| /* -*- Mode: C; indent-tabs-mode:t ; c-basic-offset:8 -*- */ |
| /* |
| * I/O functions for libusb |
| * Copyright © 2007-2009 Daniel Drake <dsd@gentoo.org> |
| * Copyright © 2001 Johannes Erdfelt <johannes@erdfelt.com> |
| * Copyright © 2019 Nathan Hjelm <hjelmn@cs.umm.edu> |
| * Copyright © 2019 Google LLC. All rights reserved. |
| * |
| * This library is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU Lesser General Public |
| * License as published by the Free Software Foundation; either |
| * version 2.1 of the License, or (at your option) any later version. |
| * |
| * This library is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * Lesser General Public License for more details. |
| * |
| * You should have received a copy of the GNU Lesser General Public |
| * License along with this library; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| |
| #include "libusbi.h" |
| #include "hotplug.h" |
| |
| #include <errno.h> |
| |
| /** |
| * \page libusb_io Synchronous and asynchronous device I/O |
| * |
| * \section io_intro Introduction |
| * |
| * If you're using libusb in your application, you're probably wanting to |
| * perform I/O with devices - you want to perform USB data transfers. |
| * |
| * libusb offers two separate interfaces for device I/O. This page aims to |
| * introduce the two in order to help you decide which one is more suitable |
| * for your application. You can also choose to use both interfaces in your |
| * application by considering each transfer on a case-by-case basis. |
| * |
| * Once you have read through the following discussion, you should consult the |
| * detailed API documentation pages for the details: |
| * - \ref libusb_syncio |
| * - \ref libusb_asyncio |
| * |
| * \section theory Transfers at a logical level |
| * |
| * At a logical level, USB transfers typically happen in two parts. For |
| * example, when reading data from a endpoint: |
| * -# A request for data is sent to the device |
| * -# Some time later, the incoming data is received by the host |
| * |
| * or when writing data to an endpoint: |
| * |
| * -# The data is sent to the device |
| * -# Some time later, the host receives acknowledgement from the device that |
| * the data has been transferred. |
| * |
| * There may be an indefinite delay between the two steps. Consider a |
| * fictional USB input device with a button that the user can press. In order |
| * to determine when the button is pressed, you would likely submit a request |
| * to read data on a bulk or interrupt endpoint and wait for data to arrive. |
| * Data will arrive when the button is pressed by the user, which is |
| * potentially hours later. |
| * |
| * libusb offers both a synchronous and an asynchronous interface to performing |
| * USB transfers. The main difference is that the synchronous interface |
| * combines both steps indicated above into a single function call, whereas |
| * the asynchronous interface separates them. |
| * |
| * \section sync The synchronous interface |
| * |
| * The synchronous I/O interface allows you to perform a USB transfer with |
| * a single function call. When the function call returns, the transfer has |
| * completed and you can parse the results. |
| * |
| * If you have used the libusb-0.1 before, this I/O style will seem familiar to |
| * you. libusb-0.1 only offered a synchronous interface. |
| * |
| * In our input device example, to read button presses you might write code |
| * in the following style: |
| \code |
| unsigned char data[4]; |
| int actual_length; |
| int r = libusb_bulk_transfer(dev_handle, LIBUSB_ENDPOINT_IN, data, sizeof(data), &actual_length, 0); |
| if (r == 0 && actual_length == sizeof(data)) { |
| // results of the transaction can now be found in the data buffer |
| // parse them here and report button press |
| } else { |
| error(); |
| } |
| \endcode |
| * |
| * The main advantage of this model is simplicity: you did everything with |
| * a single simple function call. |
| * |
| * However, this interface has its limitations. Your application will sleep |
| * inside libusb_bulk_transfer() until the transaction has completed. If it |
| * takes the user 3 hours to press the button, your application will be |
| * sleeping for that long. Execution will be tied up inside the library - |
| * the entire thread will be useless for that duration. |
| * |
| * Another issue is that by tying up the thread with that single transaction |
| * there is no possibility of performing I/O with multiple endpoints and/or |
| * multiple devices simultaneously, unless you resort to creating one thread |
| * per transaction. |
| * |
| * Additionally, there is no opportunity to cancel the transfer after the |
| * request has been submitted. |
| * |
| * For details on how to use the synchronous API, see the |
| * \ref libusb_syncio "synchronous I/O API documentation" pages. |
| * |
| * \section async The asynchronous interface |
| * |
| * Asynchronous I/O is the most significant new feature in libusb-1.0. |
| * Although it is a more complex interface, it solves all the issues detailed |
| * above. |
| * |
| * Instead of providing which functions that block until the I/O has complete, |
| * libusb's asynchronous interface presents non-blocking functions which |
| * begin a transfer and then return immediately. Your application passes a |
| * callback function pointer to this non-blocking function, which libusb will |
| * call with the results of the transaction when it has completed. |
| * |
| * Transfers which have been submitted through the non-blocking functions |
| * can be cancelled with a separate function call. |
| * |
| * The non-blocking nature of this interface allows you to be simultaneously |
| * performing I/O to multiple endpoints on multiple devices, without having |
| * to use threads. |
| * |
| * This added flexibility does come with some complications though: |
| * - In the interest of being a lightweight library, libusb does not create |
| * threads and can only operate when your application is calling into it. Your |
| * application must call into libusb from it's main loop when events are ready |
| * to be handled, or you must use some other scheme to allow libusb to |
| * undertake whatever work needs to be done. |
| * - libusb also needs to be called into at certain fixed points in time in |
| * order to accurately handle transfer timeouts. |
| * - Memory handling becomes more complex. You cannot use stack memory unless |
| * the function with that stack is guaranteed not to return until the transfer |
| * callback has finished executing. |
| * - You generally lose some linearity from your code flow because submitting |
| * the transfer request is done in a separate function from where the transfer |
| * results are handled. This becomes particularly obvious when you want to |
| * submit a second transfer based on the results of an earlier transfer. |
| * |
| * Internally, libusb's synchronous interface is expressed in terms of function |
| * calls to the asynchronous interface. |
| * |
| * For details on how to use the asynchronous API, see the |
| * \ref libusb_asyncio "asynchronous I/O API" documentation pages. |
| */ |
| |
| |
| /** |
| * \page libusb_packetoverflow Packets and overflows |
| * |
| * \section packets Packet abstraction |
| * |
| * The USB specifications describe how data is transmitted in packets, with |
| * constraints on packet size defined by endpoint descriptors. The host must |
| * not send data payloads larger than the endpoint's maximum packet size. |
| * |
| * libusb and the underlying OS abstract out the packet concept, allowing you |
| * to request transfers of any size. Internally, the request will be divided |
| * up into correctly-sized packets. You do not have to be concerned with |
| * packet sizes, but there is one exception when considering overflows. |
| * |
| * \section overflow Bulk/interrupt transfer overflows |
| * |
| * When requesting data on a bulk endpoint, libusb requires you to supply a |
| * buffer and the maximum number of bytes of data that libusb can put in that |
| * buffer. However, the size of the buffer is not communicated to the device - |
| * the device is just asked to send any amount of data. |
| * |
| * There is no problem if the device sends an amount of data that is less than |
| * or equal to the buffer size. libusb reports this condition to you through |
| * the \ref libusb_transfer::actual_length "libusb_transfer.actual_length" |
| * field. |
| * |
| * Problems may occur if the device attempts to send more data than can fit in |
| * the buffer. libusb reports LIBUSB_TRANSFER_OVERFLOW for this condition but |
| * other behaviour is largely undefined: actual_length may or may not be |
| * accurate, the chunk of data that can fit in the buffer (before overflow) |
| * may or may not have been transferred. |
| * |
| * Overflows are nasty, but can be avoided. Even though you were told to |
| * ignore packets above, think about the lower level details: each transfer is |
| * split into packets (typically small, with a maximum size of 512 bytes). |
| * Overflows can only happen if the final packet in an incoming data transfer |
| * is smaller than the actual packet that the device wants to transfer. |
| * Therefore, you will never see an overflow if your transfer buffer size is a |
| * multiple of the endpoint's packet size: the final packet will either |
| * fill up completely or will be only partially filled. |
| */ |
| |
| /** |
| * @defgroup libusb_asyncio Asynchronous device I/O |
| * |
| * This page details libusb's asynchronous (non-blocking) API for USB device |
| * I/O. This interface is very powerful but is also quite complex - you will |
| * need to read this page carefully to understand the necessary considerations |
| * and issues surrounding use of this interface. Simplistic applications |
| * may wish to consider the \ref libusb_syncio "synchronous I/O API" instead. |
| * |
| * The asynchronous interface is built around the idea of separating transfer |
| * submission and handling of transfer completion (the synchronous model |
| * combines both of these into one). There may be a long delay between |
| * submission and completion, however the asynchronous submission function |
| * is non-blocking so will return control to your application during that |
| * potentially long delay. |
| * |
| * \section asyncabstraction Transfer abstraction |
| * |
| * For the asynchronous I/O, libusb implements the concept of a generic |
| * transfer entity for all types of I/O (control, bulk, interrupt, |
| * isochronous). The generic transfer object must be treated slightly |
| * differently depending on which type of I/O you are performing with it. |
| * |
| * This is represented by the public libusb_transfer structure type. |
| * |
| * \section asynctrf Asynchronous transfers |
| * |
| * We can view asynchronous I/O as a 5 step process: |
| * -# <b>Allocation</b>: allocate a libusb_transfer |
| * -# <b>Filling</b>: populate the libusb_transfer instance with information |
| * about the transfer you wish to perform |
| * -# <b>Submission</b>: ask libusb to submit the transfer |
| * -# <b>Completion handling</b>: examine transfer results in the |
| * libusb_transfer structure |
| * -# <b>Deallocation</b>: clean up resources |
| * |
| * |
| * \subsection asyncalloc Allocation |
| * |
| * This step involves allocating memory for a USB transfer. This is the |
| * generic transfer object mentioned above. At this stage, the transfer |
| * is "blank" with no details about what type of I/O it will be used for. |
| * |
| * Allocation is done with the libusb_alloc_transfer() function. You must use |
| * this function rather than allocating your own transfers. |
| * |
| * \subsection asyncfill Filling |
| * |
| * This step is where you take a previously allocated transfer and fill it |
| * with information to determine the message type and direction, data buffer, |
| * callback function, etc. |
| * |
| * You can either fill the required fields yourself or you can use the |
| * helper functions: libusb_fill_control_transfer(), libusb_fill_bulk_transfer() |
| * and libusb_fill_interrupt_transfer(). |
| * |
| * \subsection asyncsubmit Submission |
| * |
| * When you have allocated a transfer and filled it, you can submit it using |
| * libusb_submit_transfer(). This function returns immediately but can be |
| * regarded as firing off the I/O request in the background. |
| * |
| * \subsection asynccomplete Completion handling |
| * |
| * After a transfer has been submitted, one of four things can happen to it: |
| * |
| * - The transfer completes (i.e. some data was transferred) |
| * - The transfer has a timeout and the timeout expires before all data is |
| * transferred |
| * - The transfer fails due to an error |
| * - The transfer is cancelled |
| * |
| * Each of these will cause the user-specified transfer callback function to |
| * be invoked. It is up to the callback function to determine which of the |
| * above actually happened and to act accordingly. |
| * |
| * The user-specified callback is passed a pointer to the libusb_transfer |
| * structure which was used to setup and submit the transfer. At completion |
| * time, libusb has populated this structure with results of the transfer: |
| * success or failure reason, number of bytes of data transferred, etc. See |
| * the libusb_transfer structure documentation for more information. |
| * |
| * <b>Important Note</b>: The user-specified callback is called from an event |
| * handling context. It is therefore important that no calls are made into |
| * libusb that will attempt to perform any event handling. Examples of such |
| * functions are any listed in the \ref libusb_syncio "synchronous API" and any of |
| * the blocking functions that retrieve \ref libusb_desc "USB descriptors". |
| * |
| * \subsection Deallocation |
| * |
| * When a transfer has completed (i.e. the callback function has been invoked), |
| * you are advised to free the transfer (unless you wish to resubmit it, see |
| * below). Transfers are deallocated with libusb_free_transfer(). |
| * |
| * It is undefined behaviour to free a transfer which has not completed. |
| * |
| * \section asyncresubmit Resubmission |
| * |
| * You may be wondering why allocation, filling, and submission are all |
| * separated above where they could reasonably be combined into a single |
| * operation. |
| * |
| * The reason for separation is to allow you to resubmit transfers without |
| * having to allocate new ones every time. This is especially useful for |
| * common situations dealing with interrupt endpoints - you allocate one |
| * transfer, fill and submit it, and when it returns with results you just |
| * resubmit it for the next interrupt. |
| * |
| * \section asynccancel Cancellation |
| * |
| * Another advantage of using the asynchronous interface is that you have |
| * the ability to cancel transfers which have not yet completed. This is |
| * done by calling the libusb_cancel_transfer() function. |
| * |
| * libusb_cancel_transfer() is asynchronous/non-blocking in itself. When the |
| * cancellation actually completes, the transfer's callback function will |
| * be invoked, and the callback function should check the transfer status to |
| * determine that it was cancelled. |
| * |
| * Freeing the transfer after it has been cancelled but before cancellation |
| * has completed will result in undefined behaviour. |
| * |
| * \attention |
| * When a transfer is cancelled, some of the data may have been transferred. |
| * libusb will communicate this to you in the transfer callback. |
| * <b>Do not assume that no data was transferred.</b> |
| * |
| * \section asyncpartial Partial data transfer resulting from cancellation |
| * |
| * As noted above, some of the data may have been transferred at the time a |
| * transfer is cancelled. It is helpful to see how this is possible if you |
| * consider a bulk transfer to an endpoint with a packet size of 64 bytes. |
| * Supposing you submit a 512-byte transfer to this endpoint, the operating |
| * system will divide this transfer up into 8 separate 64-byte frames that the |
| * host controller will schedule for the device to transfer data. If this |
| * transfer is cancelled while the device is transferring data, a subset of |
| * these frames may be descheduled from the host controller before the device |
| * has the opportunity to finish transferring data to the host. |
| * |
| * What your application should do with a partial data transfer is a policy |
| * decision; there is no single answer that satisfies the needs of every |
| * application. The data that was successfully transferred should be |
| * considered entirely valid, but your application must decide what to do with |
| * the remaining data that was not transferred. Some possible actions to take |
| * are: |
| * - Resubmit another transfer for the remaining data, possibly with a shorter |
| * timeout |
| * - Discard the partially transferred data and report an error |
| * |
| * \section asynctimeout Timeouts |
| * |
| * When a transfer times out, libusb internally notes this and attempts to |
| * cancel the transfer. As noted in \ref asyncpartial "above", it is possible |
| * that some of the data may actually have been transferred. Your application |
| * should <b>always</b> check how much data was actually transferred once the |
| * transfer completes and act accordingly. |
| * |
| * \section bulk_overflows Overflows on device-to-host bulk/interrupt endpoints |
| * |
| * If your device does not have predictable transfer sizes (or it misbehaves), |
| * your application may submit a request for data on an IN endpoint which is |
| * smaller than the data that the device wishes to send. In some circumstances |
| * this will cause an overflow, which is a nasty condition to deal with. See |
| * the \ref libusb_packetoverflow page for discussion. |
| * |
| * \section asyncctrl Considerations for control transfers |
| * |
| * The <tt>libusb_transfer</tt> structure is generic and hence does not |
| * include specific fields for the control-specific setup packet structure. |
| * |
| * In order to perform a control transfer, you must place the 8-byte setup |
| * packet at the start of the data buffer. To simplify this, you could |
| * cast the buffer pointer to type struct libusb_control_setup, or you can |
| * use the helper function libusb_fill_control_setup(). |
| * |
| * The wLength field placed in the setup packet must be the length you would |
| * expect to be sent in the setup packet: the length of the payload that |
| * follows (or the expected maximum number of bytes to receive). However, |
| * the length field of the libusb_transfer object must be the length of |
| * the data buffer - i.e. it should be wLength <em>plus</em> the size of |
| * the setup packet (LIBUSB_CONTROL_SETUP_SIZE). |
| * |
| * If you use the helper functions, this is simplified for you: |
| * -# Allocate a buffer of size LIBUSB_CONTROL_SETUP_SIZE plus the size of the |
| * data you are sending/requesting. |
| * -# Call libusb_fill_control_setup() on the data buffer, using the transfer |
| * request size as the wLength value (i.e. do not include the extra space you |
| * allocated for the control setup). |
| * -# If this is a host-to-device transfer, place the data to be transferred |
| * in the data buffer, starting at offset LIBUSB_CONTROL_SETUP_SIZE. |
| * -# Call libusb_fill_control_transfer() to associate the data buffer with |
| * the transfer (and to set the remaining details such as callback and timeout). |
| * - Note that there is no parameter to set the length field of the transfer. |
| * The length is automatically inferred from the wLength field of the setup |
| * packet. |
| * -# Submit the transfer. |
| * |
| * The multi-byte control setup fields (wValue, wIndex and wLength) must |
| * be given in little-endian byte order (the endianness of the USB bus). |
| * Endianness conversion is transparently handled by |
| * libusb_fill_control_setup() which is documented to accept host-endian |
| * values. |
| * |
| * Further considerations are needed when handling transfer completion in |
| * your callback function: |
| * - As you might expect, the setup packet will still be sitting at the start |
| * of the data buffer. |
| * - If this was a device-to-host transfer, the received data will be sitting |
| * at offset LIBUSB_CONTROL_SETUP_SIZE into the buffer. |
| * - The actual_length field of the transfer structure is relative to the |
| * wLength of the setup packet, rather than the size of the data buffer. So, |
| * if your wLength was 4, your transfer's <tt>length</tt> was 12, then you |
| * should expect an <tt>actual_length</tt> of 4 to indicate that the data was |
| * transferred in entirety. |
| * |
| * To simplify parsing of setup packets and obtaining the data from the |
| * correct offset, you may wish to use the libusb_control_transfer_get_data() |
| * and libusb_control_transfer_get_setup() functions within your transfer |
| * callback. |
| * |
| * Even though control endpoints do not halt, a completed control transfer |
| * may have a LIBUSB_TRANSFER_STALL status code. This indicates the control |
| * request was not supported. |
| * |
| * \section asyncintr Considerations for interrupt transfers |
| * |
| * All interrupt transfers are performed using the polling interval presented |
| * by the bInterval value of the endpoint descriptor. |
| * |
| * \section asynciso Considerations for isochronous transfers |
| * |
| * Isochronous transfers are more complicated than transfers to |
| * non-isochronous endpoints. |
| * |
| * To perform I/O to an isochronous endpoint, allocate the transfer by calling |
| * libusb_alloc_transfer() with an appropriate number of isochronous packets. |
| * |
| * During filling, set \ref libusb_transfer::type "type" to |
| * \ref libusb_transfer_type::LIBUSB_TRANSFER_TYPE_ISOCHRONOUS |
| * "LIBUSB_TRANSFER_TYPE_ISOCHRONOUS", and set |
| * \ref libusb_transfer::num_iso_packets "num_iso_packets" to a value less than |
| * or equal to the number of packets you requested during allocation. |
| * libusb_alloc_transfer() does not set either of these fields for you, given |
| * that you might not even use the transfer on an isochronous endpoint. |
| * |
| * Next, populate the length field for the first num_iso_packets entries in |
| * the \ref libusb_transfer::iso_packet_desc "iso_packet_desc" array. Section |
| * 5.6.3 of the USB2 specifications describe how the maximum isochronous |
| * packet length is determined by the wMaxPacketSize field in the endpoint |
| * descriptor. |
| * Two functions can help you here: |
| * |
| * - libusb_get_max_iso_packet_size() is an easy way to determine the max |
| * packet size for an isochronous endpoint. Note that the maximum packet |
| * size is actually the maximum number of bytes that can be transmitted in |
| * a single microframe, therefore this function multiplies the maximum number |
| * of bytes per transaction by the number of transaction opportunities per |
| * microframe. |
| * - libusb_set_iso_packet_lengths() assigns the same length to all packets |
| * within a transfer, which is usually what you want. |
| * |
| * For outgoing transfers, you'll obviously fill the buffer and populate the |
| * packet descriptors in hope that all the data gets transferred. For incoming |
| * transfers, you must ensure the buffer has sufficient capacity for |
| * the situation where all packets transfer the full amount of requested data. |
| * |
| * Completion handling requires some extra consideration. The |
| * \ref libusb_transfer::actual_length "actual_length" field of the transfer |
| * is meaningless and should not be examined; instead you must refer to the |
| * \ref libusb_iso_packet_descriptor::actual_length "actual_length" field of |
| * each individual packet. |
| * |
| * The \ref libusb_transfer::status "status" field of the transfer is also a |
| * little misleading: |
| * - If the packets were submitted and the isochronous data microframes |
| * completed normally, status will have value |
| * \ref libusb_transfer_status::LIBUSB_TRANSFER_COMPLETED |
| * "LIBUSB_TRANSFER_COMPLETED". Note that bus errors and software-incurred |
| * delays are not counted as transfer errors; the transfer.status field may |
| * indicate COMPLETED even if some or all of the packets failed. Refer to |
| * the \ref libusb_iso_packet_descriptor::status "status" field of each |
| * individual packet to determine packet failures. |
| * - The status field will have value |
| * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR |
| * "LIBUSB_TRANSFER_ERROR" only when serious errors were encountered. |
| * - Other transfer status codes occur with normal behaviour. |
| * |
| * The data for each packet will be found at an offset into the buffer that |
| * can be calculated as if each prior packet completed in full. The |
| * libusb_get_iso_packet_buffer() and libusb_get_iso_packet_buffer_simple() |
| * functions may help you here. |
| * |
| * \section asynclimits Transfer length limitations |
| * |
| * Some operating systems may impose limits on the length of the transfer data |
| * buffer or, in the case of isochronous transfers, the length of individual |
| * isochronous packets. Such limits can be difficult for libusb to detect, so |
| * in most cases the library will simply try and submit the transfer as set up |
| * by you. If the transfer fails to submit because it is too large, |
| * libusb_submit_transfer() will return |
| * \ref libusb_error::LIBUSB_ERROR_INVALID_PARAM "LIBUSB_ERROR_INVALID_PARAM". |
| * |
| * The following are known limits for control transfer lengths. Note that this |
| * length includes the 8-byte setup packet. |
| * - Linux (4,096 bytes) |
| * - Windows (4,096 bytes) |
| * |
| * \section asyncmem Memory caveats |
| * |
| * In most circumstances, it is not safe to use stack memory for transfer |
| * buffers. This is because the function that fired off the asynchronous |
| * transfer may return before libusb has finished using the buffer, and when |
| * the function returns it's stack gets destroyed. This is true for both |
| * host-to-device and device-to-host transfers. |
| * |
| * The only case in which it is safe to use stack memory is where you can |
| * guarantee that the function owning the stack space for the buffer does not |
| * return until after the transfer's callback function has completed. In every |
| * other case, you need to use heap memory instead. |
| * |
| * \section asyncflags Fine control |
| * |
| * Through using this asynchronous interface, you may find yourself repeating |
| * a few simple operations many times. You can apply a bitwise OR of certain |
| * flags to a transfer to simplify certain things: |
| * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_SHORT_NOT_OK |
| * "LIBUSB_TRANSFER_SHORT_NOT_OK" results in transfers which transferred |
| * less than the requested amount of data being marked with status |
| * \ref libusb_transfer_status::LIBUSB_TRANSFER_ERROR "LIBUSB_TRANSFER_ERROR" |
| * (they would normally be regarded as COMPLETED) |
| * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER |
| * "LIBUSB_TRANSFER_FREE_BUFFER" allows you to ask libusb to free the transfer |
| * buffer when freeing the transfer. |
| * - \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_TRANSFER |
| * "LIBUSB_TRANSFER_FREE_TRANSFER" causes libusb to automatically free the |
| * transfer after the transfer callback returns. |
| * |
| * \section asyncevent Event handling |
| * |
| * An asynchronous model requires that libusb perform work at various |
| * points in time - namely processing the results of previously-submitted |
| * transfers and invoking the user-supplied callback function. |
| * |
| * This gives rise to the libusb_handle_events() function which your |
| * application must call into when libusb has work do to. This gives libusb |
| * the opportunity to reap pending transfers, invoke callbacks, etc. |
| * |
| * \note |
| * All event handling is performed by whichever thread calls the |
| * libusb_handle_events() function. libusb does not invoke any callbacks |
| * outside of this context. Consequently, any callbacks will be run on the |
| * thread that calls the libusb_handle_events() function. |
| * |
| * When to call the libusb_handle_events() function depends on which model |
| * your application decides to use. The 2 different approaches: |
| * |
| * -# Repeatedly call libusb_handle_events() in blocking mode from a dedicated |
| * thread. |
| * -# Integrate libusb with your application's main event loop. libusb |
| * exposes a set of file descriptors which allow you to do this. |
| * |
| * The first approach has the big advantage that it will also work on Windows |
| * were libusb' poll API for select / poll integration is not available. So |
| * if you want to support Windows and use the async API, you must use this |
| * approach, see the \ref eventthread "Using an event handling thread" section |
| * below for details. |
| * |
| * If you prefer a single threaded approach with a single central event loop, |
| * see the \ref libusb_poll "polling and timing" section for how to integrate libusb |
| * into your application's main event loop. |
| * |
| * \section eventthread Using an event handling thread |
| * |
| * Lets begin with stating the obvious: If you're going to use a separate |
| * thread for libusb event handling, your callback functions MUST be |
| * thread-safe. |
| * |
| * Other then that doing event handling from a separate thread, is mostly |
| * simple. You can use an event thread function as follows: |
| \code |
| void *event_thread_func(void *ctx) |
| { |
| while (event_thread_run) |
| libusb_handle_events(ctx); |
| |
| return NULL; |
| } |
| \endcode |
| * |
| * There is one caveat though, stopping this thread requires setting the |
| * event_thread_run variable to 0, and after that libusb_handle_events() needs |
| * to return control to event_thread_func. But unless some event happens, |
| * libusb_handle_events() will not return. |
| * |
| * There are 2 different ways of dealing with this, depending on if your |
| * application uses libusb' \ref libusb_hotplug "hotplug" support or not. |
| * |
| * Applications which do not use hotplug support, should not start the event |
| * thread until after their first call to libusb_open(), and should stop the |
| * thread when closing the last open device as follows: |
| \code |
| void my_close_handle(libusb_device_handle *dev_handle) |
| { |
| if (open_devs == 1) |
| event_thread_run = 0; |
| |
| libusb_close(dev_handle); // This wakes up libusb_handle_events() |
| |
| if (open_devs == 1) |
| pthread_join(event_thread); |
| |
| open_devs--; |
| } |
| \endcode |
| * |
| * Applications using hotplug support should start the thread at program init, |
| * after having successfully called libusb_hotplug_register_callback(), and |
| * should stop the thread at program exit as follows: |
| \code |
| void my_libusb_exit(void) |
| { |
| event_thread_run = 0; |
| libusb_hotplug_deregister_callback(ctx, hotplug_cb_handle); // This wakes up libusb_handle_events() |
| pthread_join(event_thread); |
| libusb_exit(ctx); |
| } |
| \endcode |
| */ |
| |
| /** |
| * @defgroup libusb_poll Polling and timing |
| * |
| * This page documents libusb's functions for polling events and timing. |
| * These functions are only necessary for users of the |
| * \ref libusb_asyncio "asynchronous API". If you are only using the simpler |
| * \ref libusb_syncio "synchronous API" then you do not need to ever call these |
| * functions. |
| * |
| * The justification for the functionality described here has already been |
| * discussed in the \ref asyncevent "event handling" section of the |
| * asynchronous API documentation. In summary, libusb does not create internal |
| * threads for event processing and hence relies on your application calling |
| * into libusb at certain points in time so that pending events can be handled. |
| * |
| * Your main loop is probably already calling poll() or select() or a |
| * variant on a set of file descriptors for other event sources (e.g. keyboard |
| * button presses, mouse movements, network sockets, etc). You then add |
| * libusb's file descriptors to your poll()/select() calls, and when activity |
| * is detected on such descriptors you know it is time to call |
| * libusb_handle_events(). |
| * |
| * There is one final event handling complication. libusb supports |
| * asynchronous transfers which time out after a specified time period. |
| * |
| * On some platforms a timerfd is used, so the timeout handling is just another |
| * fd, on other platforms this requires that libusb is called into at or after |
| * the timeout to handle it. So, in addition to considering libusb's file |
| * descriptors in your main event loop, you must also consider that libusb |
| * sometimes needs to be called into at fixed points in time even when there |
| * is no file descriptor activity, see \ref polltime details. |
| * |
| * In order to know precisely when libusb needs to be called into, libusb |
| * offers you a set of pollable file descriptors and information about when |
| * the next timeout expires. |
| * |
| * If you are using the asynchronous I/O API, you must take one of the two |
| * following options, otherwise your I/O will not complete. |
| * |
| * \section pollsimple The simple option |
| * |
| * If your application revolves solely around libusb and does not need to |
| * handle other event sources, you can have a program structure as follows: |
| \code |
| // initialize libusb |
| // find and open device |
| // maybe fire off some initial async I/O |
| |
| while (user_has_not_requested_exit) |
| libusb_handle_events(ctx); |
| |
| // clean up and exit |
| \endcode |
| * |
| * With such a simple main loop, you do not have to worry about managing |
| * sets of file descriptors or handling timeouts. libusb_handle_events() will |
| * handle those details internally. |
| * |
| * \section libusb_pollmain The more advanced option |
| * |
| * \note This functionality is currently only available on Unix-like platforms. |
| * On Windows, libusb_get_pollfds() simply returns NULL. Applications which |
| * want to support Windows are advised to use an \ref eventthread |
| * "event handling thread" instead. |
| * |
| * In more advanced applications, you will already have a main loop which |
| * is monitoring other event sources: network sockets, X11 events, mouse |
| * movements, etc. Through exposing a set of file descriptors, libusb is |
| * designed to cleanly integrate into such main loops. |
| * |
| * In addition to polling file descriptors for the other event sources, you |
| * take a set of file descriptors from libusb and monitor those too. When you |
| * detect activity on libusb's file descriptors, you call |
| * libusb_handle_events_timeout() in non-blocking mode. |
| * |
| * What's more, libusb may also need to handle events at specific moments in |
| * time. No file descriptor activity is generated at these times, so your |
| * own application needs to be continually aware of when the next one of these |
| * moments occurs (through calling libusb_get_next_timeout()), and then it |
| * needs to call libusb_handle_events_timeout() in non-blocking mode when |
| * these moments occur. This means that you need to adjust your |
| * poll()/select() timeout accordingly. |
| * |
| * libusb provides you with a set of file descriptors to poll and expects you |
| * to poll all of them, treating them as a single entity. The meaning of each |
| * file descriptor in the set is an internal implementation detail, |
| * platform-dependent and may vary from release to release. Don't try and |
| * interpret the meaning of the file descriptors, just do as libusb indicates, |
| * polling all of them at once. |
| * |
| * In pseudo-code, you want something that looks like: |
| \code |
| // initialise libusb |
| |
| libusb_get_pollfds(ctx) |
| while (user has not requested application exit) { |
| libusb_get_next_timeout(ctx); |
| poll(on libusb file descriptors plus any other event sources of interest, |
| using a timeout no larger than the value libusb just suggested) |
| if (poll() indicated activity on libusb file descriptors) |
| libusb_handle_events_timeout(ctx, &zero_tv); |
| if (time has elapsed to or beyond the libusb timeout) |
| libusb_handle_events_timeout(ctx, &zero_tv); |
| // handle events from other sources here |
| } |
| |
| // clean up and exit |
| \endcode |
| * |
| * \subsection polltime Notes on time-based events |
| * |
| * The above complication with having to track time and call into libusb at |
| * specific moments is a bit of a headache. For maximum compatibility, you do |
| * need to write your main loop as above, but you may decide that you can |
| * restrict the supported platforms of your application and get away with |
| * a more simplistic scheme. |
| * |
| * These time-based event complications are \b not required on the following |
| * platforms: |
| * - Darwin |
| * - Linux, provided that the following version requirements are satisfied: |
| * - Linux v2.6.27 or newer, compiled with timerfd support |
| * - glibc v2.9 or newer |
| * - libusb v1.0.5 or newer |
| * |
| * Under these configurations, libusb_get_next_timeout() will \em always return |
| * 0, so your main loop can be simplified to: |
| \code |
| // initialise libusb |
| |
| libusb_get_pollfds(ctx) |
| while (user has not requested application exit) { |
| poll(on libusb file descriptors plus any other event sources of interest, |
| using any timeout that you like) |
| if (poll() indicated activity on libusb file descriptors) |
| libusb_handle_events_timeout(ctx, &zero_tv); |
| // handle events from other sources here |
| } |
| |
| // clean up and exit |
| \endcode |
| * |
| * Do remember that if you simplify your main loop to the above, you will |
| * lose compatibility with some platforms (including legacy Linux platforms, |
| * and <em>any future platforms supported by libusb which may have time-based |
| * event requirements</em>). The resultant problems will likely appear as |
| * strange bugs in your application. |
| * |
| * You can use the libusb_pollfds_handle_timeouts() function to do a runtime |
| * check to see if it is safe to ignore the time-based event complications. |
| * If your application has taken the shortcut of ignoring libusb's next timeout |
| * in your main loop, then you are advised to check the return value of |
| * libusb_pollfds_handle_timeouts() during application startup, and to abort |
| * if the platform does suffer from these timing complications. |
| * |
| * \subsection fdsetchange Changes in the file descriptor set |
| * |
| * The set of file descriptors that libusb uses as event sources may change |
| * during the life of your application. Rather than having to repeatedly |
| * call libusb_get_pollfds(), you can set up notification functions for when |
| * the file descriptor set changes using libusb_set_pollfd_notifiers(). |
| * |
| * \subsection mtissues Multi-threaded considerations |
| * |
| * Unfortunately, the situation is complicated further when multiple threads |
| * come into play. If two threads are monitoring the same file descriptors, |
| * the fact that only one thread will be woken up when an event occurs causes |
| * some headaches. |
| * |
| * The events lock, event waiters lock, and libusb_handle_events_locked() |
| * entities are added to solve these problems. You do not need to be concerned |
| * with these entities otherwise. |
| * |
| * See the extra documentation: \ref libusb_mtasync |
| */ |
| |
| /** \page libusb_mtasync Multi-threaded applications and asynchronous I/O |
| * |
| * libusb is a thread-safe library, but extra considerations must be applied |
| * to applications which interact with libusb from multiple threads. |
| * |
| * The underlying issue that must be addressed is that all libusb I/O |
| * revolves around monitoring file descriptors through the poll()/select() |
| * system calls. This is directly exposed at the |
| * \ref libusb_asyncio "asynchronous interface" but it is important to note that the |
| * \ref libusb_syncio "synchronous interface" is implemented on top of the |
| * asynchronous interface, therefore the same considerations apply. |
| * |
| * The issue is that if two or more threads are concurrently calling poll() |
| * or select() on libusb's file descriptors then only one of those threads |
| * will be woken up when an event arrives. The others will be completely |
| * oblivious that anything has happened. |
| * |
| * Consider the following pseudo-code, which submits an asynchronous transfer |
| * then waits for its completion. This style is one way you could implement a |
| * synchronous interface on top of the asynchronous interface (and libusb |
| * does something similar, albeit more advanced due to the complications |
| * explained on this page). |
| * |
| \code |
| void cb(struct libusb_transfer *transfer) |
| { |
| int *completed = transfer->user_data; |
| *completed = 1; |
| } |
| |
| void myfunc() { |
| struct libusb_transfer *transfer; |
| unsigned char buffer[LIBUSB_CONTROL_SETUP_SIZE] __attribute__ ((aligned (2))); |
| int completed = 0; |
| |
| transfer = libusb_alloc_transfer(0); |
| libusb_fill_control_setup(buffer, |
| LIBUSB_REQUEST_TYPE_VENDOR | LIBUSB_ENDPOINT_OUT, 0x04, 0x01, 0, 0); |
| libusb_fill_control_transfer(transfer, dev, buffer, cb, &completed, 1000); |
| libusb_submit_transfer(transfer); |
| |
| while (!completed) { |
| poll(libusb file descriptors, 120*1000); |
| if (poll indicates activity) |
| libusb_handle_events_timeout(ctx, &zero_tv); |
| } |
| printf("completed!"); |
| // other code here |
| } |
| \endcode |
| * |
| * Here we are <em>serializing</em> completion of an asynchronous event |
| * against a condition - the condition being completion of a specific transfer. |
| * The poll() loop has a long timeout to minimize CPU usage during situations |
| * when nothing is happening (it could reasonably be unlimited). |
| * |
| * If this is the only thread that is polling libusb's file descriptors, there |
| * is no problem: there is no danger that another thread will swallow up the |
| * event that we are interested in. On the other hand, if there is another |
| * thread polling the same descriptors, there is a chance that it will receive |
| * the event that we were interested in. In this situation, <tt>myfunc()</tt> |
| * will only realise that the transfer has completed on the next iteration of |
| * the loop, <em>up to 120 seconds later.</em> Clearly a two-minute delay is |
| * undesirable, and don't even think about using short timeouts to circumvent |
| * this issue! |
| * |
| * The solution here is to ensure that no two threads are ever polling the |
| * file descriptors at the same time. A naive implementation of this would |
| * impact the capabilities of the library, so libusb offers the scheme |
| * documented below to ensure no loss of functionality. |
| * |
| * Before we go any further, it is worth mentioning that all libusb-wrapped |
| * event handling procedures fully adhere to the scheme documented below. |
| * This includes libusb_handle_events() and its variants, and all the |
| * synchronous I/O functions - libusb hides this headache from you. |
| * |
| * \section Using libusb_handle_events() from multiple threads |
| * |
| * Even when only using libusb_handle_events() and synchronous I/O functions, |
| * you can still have a race condition. You might be tempted to solve the |
| * above with libusb_handle_events() like so: |
| * |
| \code |
| libusb_submit_transfer(transfer); |
| |
| while (!completed) { |
| libusb_handle_events(ctx); |
| } |
| printf("completed!"); |
| \endcode |
| * |
| * This however has a race between the checking of completed and |
| * libusb_handle_events() acquiring the events lock, so another thread |
| * could have completed the transfer, resulting in this thread hanging |
| * until either a timeout or another event occurs. See also commit |
| * 6696512aade99bb15d6792af90ae329af270eba6 which fixes this in the |
| * synchronous API implementation of libusb. |
| * |
| * Fixing this race requires checking the variable completed only after |
| * taking the event lock, which defeats the concept of just calling |
| * libusb_handle_events() without worrying about locking. This is why |
| * libusb-1.0.9 introduces the new libusb_handle_events_timeout_completed() |
| * and libusb_handle_events_completed() functions, which handles doing the |
| * completion check for you after they have acquired the lock: |
| * |
| \code |
| libusb_submit_transfer(transfer); |
| |
| while (!completed) { |
| libusb_handle_events_completed(ctx, &completed); |
| } |
| printf("completed!"); |
| \endcode |
| * |
| * This nicely fixes the race in our example. Note that if all you want to |
| * do is submit a single transfer and wait for its completion, then using |
| * one of the synchronous I/O functions is much easier. |
| * |
| * \note |
| * The `completed` variable must be modified while holding the event lock, |
| * otherwise a race condition can still exist. It is simplest to do so from |
| * within the transfer callback as shown above. |
| * |
| * \section eventlock The events lock |
| * |
| * The problem is when we consider the fact that libusb exposes file |
| * descriptors to allow for you to integrate asynchronous USB I/O into |
| * existing main loops, effectively allowing you to do some work behind |
| * libusb's back. If you do take libusb's file descriptors and pass them to |
| * poll()/select() yourself, you need to be aware of the associated issues. |
| * |
| * The first concept to be introduced is the events lock. The events lock |
| * is used to serialize threads that want to handle events, such that only |
| * one thread is handling events at any one time. |
| * |
| * You must take the events lock before polling libusb file descriptors, |
| * using libusb_lock_events(). You must release the lock as soon as you have |
| * aborted your poll()/select() loop, using libusb_unlock_events(). |
| * |
| * \section threadwait Letting other threads do the work for you |
| * |
| * Although the events lock is a critical part of the solution, it is not |
| * enough on it's own. You might wonder if the following is sufficient... |
| \code |
| libusb_lock_events(ctx); |
| while (!completed) { |
| poll(libusb file descriptors, 120*1000); |
| if (poll indicates activity) |
| libusb_handle_events_timeout(ctx, &zero_tv); |
| } |
| libusb_unlock_events(ctx); |
| \endcode |
| * ...and the answer is that it is not. This is because the transfer in the |
| * code shown above may take a long time (say 30 seconds) to complete, and |
| * the lock is not released until the transfer is completed. |
| * |
| * Another thread with similar code that wants to do event handling may be |
| * working with a transfer that completes after a few milliseconds. Despite |
| * having such a quick completion time, the other thread cannot check that |
| * status of its transfer until the code above has finished (30 seconds later) |
| * due to contention on the lock. |
| * |
| * To solve this, libusb offers you a mechanism to determine when another |
| * thread is handling events. It also offers a mechanism to block your thread |
| * until the event handling thread has completed an event (and this mechanism |
| * does not involve polling of file descriptors). |
| * |
| * After determining that another thread is currently handling events, you |
| * obtain the <em>event waiters</em> lock using libusb_lock_event_waiters(). |
| * You then re-check that some other thread is still handling events, and if |
| * so, you call libusb_wait_for_event(). |
| * |
| * libusb_wait_for_event() puts your application to sleep until an event |
| * occurs, or until a thread releases the events lock. When either of these |
| * things happen, your thread is woken up, and should re-check the condition |
| * it was waiting on. It should also re-check that another thread is handling |
| * events, and if not, it should start handling events itself. |
| * |
| * This looks like the following, as pseudo-code: |
| \code |
| retry: |
| if (libusb_try_lock_events(ctx) == 0) { |
| // we obtained the event lock: do our own event handling |
| while (!completed) { |
| if (!libusb_event_handling_ok(ctx)) { |
| libusb_unlock_events(ctx); |
| goto retry; |
| } |
| poll(libusb file descriptors, 120*1000); |
| if (poll indicates activity) |
| libusb_handle_events_locked(ctx, 0); |
| } |
| libusb_unlock_events(ctx); |
| } else { |
| // another thread is doing event handling. wait for it to signal us that |
| // an event has completed |
| libusb_lock_event_waiters(ctx); |
| |
| while (!completed) { |
| // now that we have the event waiters lock, double check that another |
| // thread is still handling events for us. (it may have ceased handling |
| // events in the time it took us to reach this point) |
| if (!libusb_event_handler_active(ctx)) { |
| // whoever was handling events is no longer doing so, try again |
| libusb_unlock_event_waiters(ctx); |
| goto retry; |
| } |
| |
| libusb_wait_for_event(ctx, NULL); |
| } |
| libusb_unlock_event_waiters(ctx); |
| } |
| printf("completed!\n"); |
| \endcode |
| * |
| * A naive look at the above code may suggest that this can only support |
| * one event waiter (hence a total of 2 competing threads, the other doing |
| * event handling), because the event waiter seems to have taken the event |
| * waiters lock while waiting for an event. However, the system does support |
| * multiple event waiters, because libusb_wait_for_event() actually drops |
| * the lock while waiting, and reacquires it before continuing. |
| * |
| * We have now implemented code which can dynamically handle situations where |
| * nobody is handling events (so we should do it ourselves), and it can also |
| * handle situations where another thread is doing event handling (so we can |
| * piggyback onto them). It is also equipped to handle a combination of |
| * the two, for example, another thread is doing event handling, but for |
| * whatever reason it stops doing so before our condition is met, so we take |
| * over the event handling. |
| * |
| * Four functions were introduced in the above pseudo-code. Their importance |
| * should be apparent from the code shown above. |
| * -# libusb_try_lock_events() is a non-blocking function which attempts |
| * to acquire the events lock but returns a failure code if it is contended. |
| * -# libusb_event_handling_ok() checks that libusb is still happy for your |
| * thread to be performing event handling. Sometimes, libusb needs to |
| * interrupt the event handler, and this is how you can check if you have |
| * been interrupted. If this function returns 0, the correct behaviour is |
| * for you to give up the event handling lock, and then to repeat the cycle. |
| * The following libusb_try_lock_events() will fail, so you will become an |
| * events waiter. For more information on this, read \ref fullstory below. |
| * -# libusb_handle_events_locked() is a variant of |
| * libusb_handle_events_timeout() that you can call while holding the |
| * events lock. libusb_handle_events_timeout() itself implements similar |
| * logic to the above, so be sure not to call it when you are |
| * "working behind libusb's back", as is the case here. |
| * -# libusb_event_handler_active() determines if someone is currently |
| * holding the events lock |
| * |
| * You might be wondering why there is no function to wake up all threads |
| * blocked on libusb_wait_for_event(). This is because libusb can do this |
| * internally: it will wake up all such threads when someone calls |
| * libusb_unlock_events() or when a transfer completes (at the point after its |
| * callback has returned). |
| * |
| * \subsection fullstory The full story |
| * |
| * The above explanation should be enough to get you going, but if you're |
| * really thinking through the issues then you may be left with some more |
| * questions regarding libusb's internals. If you're curious, read on, and if |
| * not, skip to the next section to avoid confusing yourself! |
| * |
| * The immediate question that may spring to mind is: what if one thread |
| * modifies the set of file descriptors that need to be polled while another |
| * thread is doing event handling? |
| * |
| * There are 2 situations in which this may happen. |
| * -# libusb_open() will add another file descriptor to the poll set, |
| * therefore it is desirable to interrupt the event handler so that it |
| * restarts, picking up the new descriptor. |
| * -# libusb_close() will remove a file descriptor from the poll set. There |
| * are all kinds of race conditions that could arise here, so it is |
| * important that nobody is doing event handling at this time. |
| * |
| * libusb handles these issues internally, so application developers do not |
| * have to stop their event handlers while opening/closing devices. Here's how |
| * it works, focusing on the libusb_close() situation first: |
| * |
| * -# During initialization, libusb opens an internal pipe, and it adds the read |
| * end of this pipe to the set of file descriptors to be polled. |
| * -# During libusb_close(), libusb writes some dummy data on this event pipe. |
| * This immediately interrupts the event handler. libusb also records |
| * internally that it is trying to interrupt event handlers for this |
| * high-priority event. |
| * -# At this point, some of the functions described above start behaving |
| * differently: |
| * - libusb_event_handling_ok() starts returning 1, indicating that it is NOT |
| * OK for event handling to continue. |
| * - libusb_try_lock_events() starts returning 1, indicating that another |
| * thread holds the event handling lock, even if the lock is uncontended. |
| * - libusb_event_handler_active() starts returning 1, indicating that |
| * another thread is doing event handling, even if that is not true. |
| * -# The above changes in behaviour result in the event handler stopping and |
| * giving up the events lock very quickly, giving the high-priority |
| * libusb_close() operation a "free ride" to acquire the events lock. All |
| * threads that are competing to do event handling become event waiters. |
| * -# With the events lock held inside libusb_close(), libusb can safely remove |
| * a file descriptor from the poll set, in the safety of knowledge that |
| * nobody is polling those descriptors or trying to access the poll set. |
| * -# After obtaining the events lock, the close operation completes very |
| * quickly (usually a matter of milliseconds) and then immediately releases |
| * the events lock. |
| * -# At the same time, the behaviour of libusb_event_handling_ok() and friends |
| * reverts to the original, documented behaviour. |
| * -# The release of the events lock causes the threads that are waiting for |
| * events to be woken up and to start competing to become event handlers |
| * again. One of them will succeed; it will then re-obtain the list of poll |
| * descriptors, and USB I/O will then continue as normal. |
| * |
| * libusb_open() is similar, and is actually a more simplistic case. Upon a |
| * call to libusb_open(): |
| * |
| * -# The device is opened and a file descriptor is added to the poll set. |
| * -# libusb sends some dummy data on the event pipe, and records that it |
| * is trying to modify the poll descriptor set. |
| * -# The event handler is interrupted, and the same behaviour change as for |
| * libusb_close() takes effect, causing all event handling threads to become |
| * event waiters. |
| * -# The libusb_open() implementation takes its free ride to the events lock. |
| * -# Happy that it has successfully paused the events handler, libusb_open() |
| * releases the events lock. |
| * -# The event waiter threads are all woken up and compete to become event |
| * handlers again. The one that succeeds will obtain the list of poll |
| * descriptors again, which will include the addition of the new device. |
| * |
| * \subsection concl Closing remarks |
| * |
| * The above may seem a little complicated, but hopefully I have made it clear |
| * why such complications are necessary. Also, do not forget that this only |
| * applies to applications that take libusb's file descriptors and integrate |
| * them into their own polling loops. |
| * |
| * You may decide that it is OK for your multi-threaded application to ignore |
| * some of the rules and locks detailed above, because you don't think that |
| * two threads can ever be polling the descriptors at the same time. If that |
| * is the case, then that's good news for you because you don't have to worry. |
| * But be careful here; remember that the synchronous I/O functions do event |
| * handling internally. If you have one thread doing event handling in a loop |
| * (without implementing the rules and locking semantics documented above) |
| * and another trying to send a synchronous USB transfer, you will end up with |
| * two threads monitoring the same descriptors, and the above-described |
| * undesirable behaviour occurring. The solution is for your polling thread to |
| * play by the rules; the synchronous I/O functions do so, and this will result |
| * in them getting along in perfect harmony. |
| * |
| * If you do have a dedicated thread doing event handling, it is perfectly |
| * legal for it to take the event handling lock for long periods of time. Any |
| * synchronous I/O functions you call from other threads will transparently |
| * fall back to the "event waiters" mechanism detailed above. The only |
| * consideration that your event handling thread must apply is the one related |
| * to libusb_event_handling_ok(): you must call this before every poll(), and |
| * give up the events lock if instructed. |
| */ |
| |
| int usbi_io_init(struct libusb_context *ctx) |
| { |
| int r; |
| |
| usbi_mutex_init(&ctx->flying_transfers_lock); |
| usbi_mutex_init(&ctx->events_lock); |
| usbi_mutex_init(&ctx->event_waiters_lock); |
| usbi_cond_init(&ctx->event_waiters_cond); |
| usbi_mutex_init(&ctx->event_data_lock); |
| usbi_tls_key_create(&ctx->event_handling_key); |
| list_init(&ctx->flying_transfers); |
| list_init(&ctx->event_sources); |
| list_init(&ctx->removed_event_sources); |
| list_init(&ctx->hotplug_msgs); |
| list_init(&ctx->completed_transfers); |
| |
| r = usbi_create_event(&ctx->event); |
| if (r < 0) |
| goto err; |
| |
| r = usbi_add_event_source(ctx, USBI_EVENT_OS_HANDLE(&ctx->event), USBI_EVENT_POLL_EVENTS); |
| if (r < 0) |
| goto err_destroy_event; |
| |
| #ifdef HAVE_OS_TIMER |
| r = usbi_create_timer(&ctx->timer); |
| if (r == 0) { |
| usbi_dbg("using timer for timeouts"); |
| r = usbi_add_event_source(ctx, USBI_TIMER_OS_HANDLE(&ctx->timer), USBI_TIMER_POLL_EVENTS); |
| if (r < 0) |
| goto err_destroy_timer; |
| } else { |
| usbi_dbg("timer not available for timeouts"); |
| } |
| #endif |
| |
| return 0; |
| |
| #ifdef HAVE_OS_TIMER |
| err_destroy_timer: |
| usbi_destroy_timer(&ctx->timer); |
| usbi_remove_event_source(ctx, USBI_EVENT_OS_HANDLE(&ctx->event)); |
| #endif |
| err_destroy_event: |
| usbi_destroy_event(&ctx->event); |
| err: |
| usbi_mutex_destroy(&ctx->flying_transfers_lock); |
| usbi_mutex_destroy(&ctx->events_lock); |
| usbi_mutex_destroy(&ctx->event_waiters_lock); |
| usbi_cond_destroy(&ctx->event_waiters_cond); |
| usbi_mutex_destroy(&ctx->event_data_lock); |
| usbi_tls_key_delete(ctx->event_handling_key); |
| return r; |
| } |
| |
| static void cleanup_removed_event_sources(struct libusb_context *ctx) |
| { |
| struct usbi_event_source *ievent_source, *tmp; |
| |
| for_each_removed_event_source_safe(ctx, ievent_source, tmp) { |
| list_del(&ievent_source->list); |
| free(ievent_source); |
| } |
| } |
| |
| void usbi_io_exit(struct libusb_context *ctx) |
| { |
| #ifdef HAVE_OS_TIMER |
| if (usbi_using_timer(ctx)) { |
| usbi_remove_event_source(ctx, USBI_TIMER_OS_HANDLE(&ctx->timer)); |
| usbi_destroy_timer(&ctx->timer); |
| } |
| #endif |
| usbi_remove_event_source(ctx, USBI_EVENT_OS_HANDLE(&ctx->event)); |
| usbi_destroy_event(&ctx->event); |
| usbi_mutex_destroy(&ctx->flying_transfers_lock); |
| usbi_mutex_destroy(&ctx->events_lock); |
| usbi_mutex_destroy(&ctx->event_waiters_lock); |
| usbi_cond_destroy(&ctx->event_waiters_cond); |
| usbi_mutex_destroy(&ctx->event_data_lock); |
| usbi_tls_key_delete(ctx->event_handling_key); |
| cleanup_removed_event_sources(ctx); |
| free(ctx->event_data); |
| } |
| |
| static int calculate_timeout(struct usbi_transfer *itransfer) |
| { |
| int r; |
| unsigned int timeout = |
| USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer)->timeout; |
| |
| if (!timeout) { |
| TIMESPEC_CLEAR(&itransfer->timeout); |
| return 0; |
| } |
| |
| r = usbi_clock_gettime(USBI_CLOCK_MONOTONIC, &itransfer->timeout); |
| if (r < 0) { |
| usbi_err(ITRANSFER_CTX(itransfer), |
| "failed to read monotonic clock, errno=%d", errno); |
| return LIBUSB_ERROR_OTHER; |
| } |
| |
| itransfer->timeout.tv_sec += timeout / 1000U; |
| itransfer->timeout.tv_nsec += (timeout % 1000U) * 1000000L; |
| if (itransfer->timeout.tv_nsec >= 1000000000L) { |
| ++itransfer->timeout.tv_sec; |
| itransfer->timeout.tv_nsec -= 1000000000L; |
| } |
| |
| return 0; |
| } |
| |
| /** \ingroup libusb_asyncio |
| * Allocate a libusb transfer with a specified number of isochronous packet |
| * descriptors. The returned transfer is pre-initialized for you. When the new |
| * transfer is no longer needed, it should be freed with |
| * libusb_free_transfer(). |
| * |
| * Transfers intended for non-isochronous endpoints (e.g. control, bulk, |
| * interrupt) should specify an iso_packets count of zero. |
| * |
| * For transfers intended for isochronous endpoints, specify an appropriate |
| * number of packet descriptors to be allocated as part of the transfer. |
| * The returned transfer is not specially initialized for isochronous I/O; |
| * you are still required to set the |
| * \ref libusb_transfer::num_iso_packets "num_iso_packets" and |
| * \ref libusb_transfer::type "type" fields accordingly. |
| * |
| * It is safe to allocate a transfer with some isochronous packets and then |
| * use it on a non-isochronous endpoint. If you do this, ensure that at time |
| * of submission, num_iso_packets is 0 and that type is set appropriately. |
| * |
| * \param iso_packets number of isochronous packet descriptors to allocate. Must be non-negative. |
| * \returns a newly allocated transfer, or NULL on error |
| */ |
| DEFAULT_VISIBILITY |
| struct libusb_transfer * LIBUSB_CALL libusb_alloc_transfer( |
| int iso_packets) |
| { |
| size_t priv_size; |
| size_t alloc_size; |
| unsigned char *ptr; |
| struct usbi_transfer *itransfer; |
| struct libusb_transfer *transfer; |
| |
| assert(iso_packets >= 0); |
| if (iso_packets < 0) |
| return NULL; |
| |
| priv_size = PTR_ALIGN(usbi_backend.transfer_priv_size); |
| alloc_size = priv_size |
| + sizeof(struct usbi_transfer) |
| + sizeof(struct libusb_transfer) |
| + (sizeof(struct libusb_iso_packet_descriptor) * (size_t)iso_packets); |
| ptr = calloc(1, alloc_size); |
| if (!ptr) |
| return NULL; |
| |
| itransfer = (struct usbi_transfer *)(ptr + priv_size); |
| itransfer->num_iso_packets = iso_packets; |
| itransfer->priv = ptr; |
| usbi_mutex_init(&itransfer->lock); |
| transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer); |
| usbi_dbg("transfer %p", transfer); |
| return transfer; |
| } |
| |
| /** \ingroup libusb_asyncio |
| * Free a transfer structure. This should be called for all transfers |
| * allocated with libusb_alloc_transfer(). |
| * |
| * If the \ref libusb_transfer_flags::LIBUSB_TRANSFER_FREE_BUFFER |
| * "LIBUSB_TRANSFER_FREE_BUFFER" flag is set and the transfer buffer is |
| * non-NULL, this function will also free the transfer buffer using the |
| * standard system memory allocator (e.g. free()). |
| * |
| * It is legal to call this function with a NULL transfer. In this case, |
| * the function will simply return safely. |
| * |
| * It is not legal to free an active transfer (one which has been submitted |
| * and has not yet completed). |
| * |
| * \param transfer the transfer to free |
| */ |
| void API_EXPORTED libusb_free_transfer(struct libusb_transfer *transfer) |
| { |
| struct usbi_transfer *itransfer; |
| size_t priv_size; |
| unsigned char *ptr; |
| |
| if (!transfer) |
| return; |
| |
| usbi_dbg("transfer %p", transfer); |
| if (transfer->flags & LIBUSB_TRANSFER_FREE_BUFFER) |
| free(transfer->buffer); |
| |
| itransfer = LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); |
| usbi_mutex_destroy(&itransfer->lock); |
| |
| priv_size = PTR_ALIGN(usbi_backend.transfer_priv_size); |
| ptr = (unsigned char *)itransfer - priv_size; |
| assert(ptr == itransfer->priv); |
| free(ptr); |
| } |
| |
| /* iterates through the flying transfers, and rearms the timer based on the |
| * next upcoming timeout. |
| * must be called with flying_list locked. |
| * returns 0 on success or a LIBUSB_ERROR code on failure. |
| */ |
| #ifdef HAVE_OS_TIMER |
| static int arm_timer_for_next_timeout(struct libusb_context *ctx) |
| { |
| struct usbi_transfer *itransfer; |
| |
| if (!usbi_using_timer(ctx)) |
| return 0; |
| |
| for_each_transfer(ctx, itransfer) { |
| struct timespec *cur_ts = &itransfer->timeout; |
| |
| /* if we've reached transfers of infinite timeout, then we have no |
| * arming to do */ |
| if (!TIMESPEC_IS_SET(cur_ts)) |
| break; |
| |
| /* act on first transfer that has not already been handled */ |
| if (!(itransfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT))) { |
| usbi_dbg("next timeout originally %ums", USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer)->timeout); |
| return usbi_arm_timer(&ctx->timer, cur_ts); |
| } |
| } |
| |
| usbi_dbg("no timeouts, disarming timer"); |
| return usbi_disarm_timer(&ctx->timer); |
| } |
| #else |
| static inline int arm_timer_for_next_timeout(struct libusb_context *ctx) |
| { |
| UNUSED(ctx); |
| return 0; |
| } |
| #endif |
| |
| /* add a transfer to the (timeout-sorted) active transfers list. |
| * This function will return non 0 if fails to update the timer, |
| * in which case the transfer is *not* on the flying_transfers list. */ |
| static int add_to_flying_list(struct usbi_transfer *itransfer) |
| { |
| struct usbi_transfer *cur; |
| struct timespec *timeout = &itransfer->timeout; |
| struct libusb_context *ctx = ITRANSFER_CTX(itransfer); |
| int r; |
| int first = 1; |
| |
| r = calculate_timeout(itransfer); |
| if (r) |
| return r; |
| |
| /* if we have no other flying transfers, start the list with this one */ |
| if (list_empty(&ctx->flying_transfers)) { |
| list_add(&itransfer->list, &ctx->flying_transfers); |
| goto out; |
| } |
| |
| /* if we have infinite timeout, append to end of list */ |
| if (!TIMESPEC_IS_SET(timeout)) { |
| list_add_tail(&itransfer->list, &ctx->flying_transfers); |
| /* first is irrelevant in this case */ |
| goto out; |
| } |
| |
| /* otherwise, find appropriate place in list */ |
| for_each_transfer(ctx, cur) { |
| /* find first timeout that occurs after the transfer in question */ |
| struct timespec *cur_ts = &cur->timeout; |
| |
| if (!TIMESPEC_IS_SET(cur_ts) || TIMESPEC_CMP(cur_ts, timeout, >)) { |
| list_add_tail(&itransfer->list, &cur->list); |
| goto out; |
| } |
| first = 0; |
| } |
| /* first is 0 at this stage (list not empty) */ |
| |
| /* otherwise we need to be inserted at the end */ |
| list_add_tail(&itransfer->list, &ctx->flying_transfers); |
| out: |
| #ifdef HAVE_OS_TIMER |
| if (first && usbi_using_timer(ctx) && TIMESPEC_IS_SET(timeout)) { |
| /* if this transfer has the lowest timeout of all active transfers, |
| * rearm the timer with this transfer's timeout */ |
| usbi_dbg("arm timer for timeout in %ums (first in line)", |
| USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer)->timeout); |
| r = usbi_arm_timer(&ctx->timer, timeout); |
| } |
| #else |
| UNUSED(first); |
| #endif |
| |
| if (r) |
| list_del(&itransfer->list); |
| |
| return r; |
| } |
| |
| /* remove a transfer from the active transfers list. |
| * This function will *always* remove the transfer from the |
| * flying_transfers list. It will return a LIBUSB_ERROR code |
| * if it fails to update the timer for the next timeout. */ |
| static int remove_from_flying_list(struct usbi_transfer *itransfer) |
| { |
| struct libusb_context *ctx = ITRANSFER_CTX(itransfer); |
| int rearm_timer; |
| int r = 0; |
| |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| rearm_timer = (TIMESPEC_IS_SET(&itransfer->timeout) && |
| list_first_entry(&ctx->flying_transfers, struct usbi_transfer, list) == itransfer); |
| list_del(&itransfer->list); |
| if (rearm_timer) |
| r = arm_timer_for_next_timeout(ctx); |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| |
| return r; |
| } |
| |
| /** \ingroup libusb_asyncio |
| * Submit a transfer. This function will fire off the USB transfer and then |
| * return immediately. |
| * |
| * \param transfer the transfer to submit |
| * \returns 0 on success |
| * \returns LIBUSB_ERROR_NO_DEVICE if the device has been disconnected |
| * \returns LIBUSB_ERROR_BUSY if the transfer has already been submitted. |
| * \returns LIBUSB_ERROR_NOT_SUPPORTED if the transfer flags are not supported |
| * by the operating system. |
| * \returns LIBUSB_ERROR_INVALID_PARAM if the transfer size is larger than |
| * the operating system and/or hardware can support (see \ref asynclimits) |
| * \returns another LIBUSB_ERROR code on other failure |
| */ |
| int API_EXPORTED libusb_submit_transfer(struct libusb_transfer *transfer) |
| { |
| struct usbi_transfer *itransfer = |
| LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); |
| struct libusb_context *ctx = TRANSFER_CTX(transfer); |
| int r; |
| |
| usbi_dbg("transfer %p", transfer); |
| |
| /* |
| * Important note on locking, this function takes / releases locks |
| * in the following order: |
| * take flying_transfers_lock |
| * take itransfer->lock |
| * clear transfer |
| * add to flying_transfers list |
| * release flying_transfers_lock |
| * submit transfer |
| * release itransfer->lock |
| * if submit failed: |
| * take flying_transfers_lock |
| * remove from flying_transfers list |
| * release flying_transfers_lock |
| * |
| * Note that it takes locks in the order a-b and then releases them |
| * in the same order a-b. This is somewhat unusual but not wrong, |
| * release order is not important as long as *all* locks are released |
| * before re-acquiring any locks. |
| * |
| * This means that the ordering of first releasing itransfer->lock |
| * and then re-acquiring the flying_transfers_list on error is |
| * important and must not be changed! |
| * |
| * This is done this way because when we take both locks we must always |
| * take flying_transfers_lock first to avoid ab-ba style deadlocks with |
| * the timeout handling and usbi_handle_disconnect paths. |
| * |
| * And we cannot release itransfer->lock before the submission is |
| * complete otherwise timeout handling for transfers with short |
| * timeouts may run before submission. |
| */ |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| usbi_mutex_lock(&itransfer->lock); |
| if (itransfer->state_flags & USBI_TRANSFER_IN_FLIGHT) { |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| usbi_mutex_unlock(&itransfer->lock); |
| return LIBUSB_ERROR_BUSY; |
| } |
| itransfer->transferred = 0; |
| itransfer->state_flags = 0; |
| itransfer->timeout_flags = 0; |
| r = add_to_flying_list(itransfer); |
| if (r) { |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| usbi_mutex_unlock(&itransfer->lock); |
| return r; |
| } |
| /* |
| * We must release the flying transfers lock here, because with |
| * some backends the submit_transfer method is synchroneous. |
| */ |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| |
| r = usbi_backend.submit_transfer(itransfer); |
| if (r == LIBUSB_SUCCESS) { |
| itransfer->state_flags |= USBI_TRANSFER_IN_FLIGHT; |
| /* keep a reference to this device */ |
| libusb_ref_device(transfer->dev_handle->dev); |
| } |
| usbi_mutex_unlock(&itransfer->lock); |
| |
| if (r != LIBUSB_SUCCESS) |
| remove_from_flying_list(itransfer); |
| |
| return r; |
| } |
| |
| /** \ingroup libusb_asyncio |
| * Asynchronously cancel a previously submitted transfer. |
| * This function returns immediately, but this does not indicate cancellation |
| * is complete. Your callback function will be invoked at some later time |
| * with a transfer status of |
| * \ref libusb_transfer_status::LIBUSB_TRANSFER_CANCELLED |
| * "LIBUSB_TRANSFER_CANCELLED." |
| * |
| * \param transfer the transfer to cancel |
| * \returns 0 on success |
| * \returns LIBUSB_ERROR_NOT_FOUND if the transfer is not in progress, |
| * already complete, or already cancelled. |
| * \returns a LIBUSB_ERROR code on failure |
| */ |
| int API_EXPORTED libusb_cancel_transfer(struct libusb_transfer *transfer) |
| { |
| struct usbi_transfer *itransfer = |
| LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); |
| int r; |
| |
| usbi_dbg("transfer %p", transfer ); |
| usbi_mutex_lock(&itransfer->lock); |
| if (!(itransfer->state_flags & USBI_TRANSFER_IN_FLIGHT) |
| || (itransfer->state_flags & USBI_TRANSFER_CANCELLING)) { |
| r = LIBUSB_ERROR_NOT_FOUND; |
| goto out; |
| } |
| r = usbi_backend.cancel_transfer(itransfer); |
| if (r < 0) { |
| if (r != LIBUSB_ERROR_NOT_FOUND && |
| r != LIBUSB_ERROR_NO_DEVICE) |
| usbi_err(TRANSFER_CTX(transfer), |
| "cancel transfer failed error %d", r); |
| else |
| usbi_dbg("cancel transfer failed error %d", r); |
| |
| if (r == LIBUSB_ERROR_NO_DEVICE) |
| itransfer->state_flags |= USBI_TRANSFER_DEVICE_DISAPPEARED; |
| } |
| |
| itransfer->state_flags |= USBI_TRANSFER_CANCELLING; |
| |
| out: |
| usbi_mutex_unlock(&itransfer->lock); |
| return r; |
| } |
| |
| /** \ingroup libusb_asyncio |
| * Set a transfers bulk stream id. Note users are advised to use |
| * libusb_fill_bulk_stream_transfer() instead of calling this function |
| * directly. |
| * |
| * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103 |
| * |
| * \param transfer the transfer to set the stream id for |
| * \param stream_id the stream id to set |
| * \see libusb_alloc_streams() |
| */ |
| void API_EXPORTED libusb_transfer_set_stream_id( |
| struct libusb_transfer *transfer, uint32_t stream_id) |
| { |
| struct usbi_transfer *itransfer = |
| LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); |
| |
| itransfer->stream_id = stream_id; |
| } |
| |
| /** \ingroup libusb_asyncio |
| * Get a transfers bulk stream id. |
| * |
| * Since version 1.0.19, \ref LIBUSB_API_VERSION >= 0x01000103 |
| * |
| * \param transfer the transfer to get the stream id for |
| * \returns the stream id for the transfer |
| */ |
| uint32_t API_EXPORTED libusb_transfer_get_stream_id( |
| struct libusb_transfer *transfer) |
| { |
| struct usbi_transfer *itransfer = |
| LIBUSB_TRANSFER_TO_USBI_TRANSFER(transfer); |
| |
| return itransfer->stream_id; |
| } |
| |
| /* Handle completion of a transfer (completion might be an error condition). |
| * This will invoke the user-supplied callback function, which may end up |
| * freeing the transfer. Therefore you cannot use the transfer structure |
| * after calling this function, and you should free all backend-specific |
| * data before calling it. |
| * Do not call this function with the usbi_transfer lock held. User-specified |
| * callback functions may attempt to directly resubmit the transfer, which |
| * will attempt to take the lock. */ |
| int usbi_handle_transfer_completion(struct usbi_transfer *itransfer, |
| enum libusb_transfer_status status) |
| { |
| struct libusb_transfer *transfer = |
| USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer); |
| struct libusb_device_handle *dev_handle = transfer->dev_handle; |
| uint8_t flags; |
| int r; |
| |
| r = remove_from_flying_list(itransfer); |
| if (r < 0) |
| usbi_err(ITRANSFER_CTX(itransfer), "failed to set timer for next timeout"); |
| |
| usbi_mutex_lock(&itransfer->lock); |
| itransfer->state_flags &= ~USBI_TRANSFER_IN_FLIGHT; |
| usbi_mutex_unlock(&itransfer->lock); |
| |
| if (status == LIBUSB_TRANSFER_COMPLETED |
| && transfer->flags & LIBUSB_TRANSFER_SHORT_NOT_OK) { |
| int rqlen = transfer->length; |
| if (transfer->type == LIBUSB_TRANSFER_TYPE_CONTROL) |
| rqlen -= LIBUSB_CONTROL_SETUP_SIZE; |
| if (rqlen != itransfer->transferred) { |
| usbi_dbg("interpreting short transfer as error"); |
| status = LIBUSB_TRANSFER_ERROR; |
| } |
| } |
| |
| flags = transfer->flags; |
| transfer->status = status; |
| transfer->actual_length = itransfer->transferred; |
| usbi_dbg("transfer %p has callback %p", transfer, transfer->callback); |
| if (transfer->callback) |
| transfer->callback(transfer); |
| /* transfer might have been freed by the above call, do not use from |
| * this point. */ |
| if (flags & LIBUSB_TRANSFER_FREE_TRANSFER) |
| libusb_free_transfer(transfer); |
| libusb_unref_device(dev_handle->dev); |
| return r; |
| } |
| |
| /* Similar to usbi_handle_transfer_completion() but exclusively for transfers |
| * that were asynchronously cancelled. The same concerns w.r.t. freeing of |
| * transfers exist here. |
| * Do not call this function with the usbi_transfer lock held. User-specified |
| * callback functions may attempt to directly resubmit the transfer, which |
| * will attempt to take the lock. */ |
| int usbi_handle_transfer_cancellation(struct usbi_transfer *itransfer) |
| { |
| struct libusb_context *ctx = ITRANSFER_CTX(itransfer); |
| uint8_t timed_out; |
| |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| timed_out = itransfer->timeout_flags & USBI_TRANSFER_TIMED_OUT; |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| |
| /* if the URB was cancelled due to timeout, report timeout to the user */ |
| if (timed_out) { |
| usbi_dbg("detected timeout cancellation"); |
| return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_TIMED_OUT); |
| } |
| |
| /* otherwise its a normal async cancel */ |
| return usbi_handle_transfer_completion(itransfer, LIBUSB_TRANSFER_CANCELLED); |
| } |
| |
| /* Add a completed transfer to the completed_transfers list of the |
| * context and signal the event. The backend's handle_transfer_completion() |
| * function will be called the next time an event handler runs. */ |
| void usbi_signal_transfer_completion(struct usbi_transfer *itransfer) |
| { |
| libusb_device_handle *dev_handle = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer)->dev_handle; |
| |
| if (dev_handle) { |
| struct libusb_context *ctx = HANDLE_CTX(dev_handle); |
| unsigned int event_flags; |
| |
| usbi_mutex_lock(&ctx->event_data_lock); |
| event_flags = ctx->event_flags; |
| ctx->event_flags |= USBI_EVENT_TRANSFER_COMPLETED; |
| list_add_tail(&itransfer->completed_list, &ctx->completed_transfers); |
| if (!event_flags) |
| usbi_signal_event(&ctx->event); |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| } |
| } |
| |
| /** \ingroup libusb_poll |
| * Attempt to acquire the event handling lock. This lock is used to ensure that |
| * only one thread is monitoring libusb event sources at any one time. |
| * |
| * You only need to use this lock if you are developing an application |
| * which calls poll() or select() on libusb's file descriptors directly. |
| * If you stick to libusb's event handling loop functions (e.g. |
| * libusb_handle_events()) then you do not need to be concerned with this |
| * locking. |
| * |
| * While holding this lock, you are trusted to actually be handling events. |
| * If you are no longer handling events, you must call libusb_unlock_events() |
| * as soon as possible. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \returns 0 if the lock was obtained successfully |
| * \returns 1 if the lock was not obtained (i.e. another thread holds the lock) |
| * \ref libusb_mtasync |
| */ |
| int API_EXPORTED libusb_try_lock_events(libusb_context *ctx) |
| { |
| int r; |
| unsigned int ru; |
| |
| ctx = usbi_get_context(ctx); |
| |
| /* is someone else waiting to close a device? if so, don't let this thread |
| * start event handling */ |
| usbi_mutex_lock(&ctx->event_data_lock); |
| ru = ctx->device_close; |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| if (ru) { |
| usbi_dbg("someone else is closing a device"); |
| return 1; |
| } |
| |
| r = usbi_mutex_trylock(&ctx->events_lock); |
| if (r) |
| return 1; |
| |
| ctx->event_handler_active = 1; |
| return 0; |
| } |
| |
| /** \ingroup libusb_poll |
| * Acquire the event handling lock, blocking until successful acquisition if |
| * it is contended. This lock is used to ensure that only one thread is |
| * monitoring libusb event sources at any one time. |
| * |
| * You only need to use this lock if you are developing an application |
| * which calls poll() or select() on libusb's file descriptors directly. |
| * If you stick to libusb's event handling loop functions (e.g. |
| * libusb_handle_events()) then you do not need to be concerned with this |
| * locking. |
| * |
| * While holding this lock, you are trusted to actually be handling events. |
| * If you are no longer handling events, you must call libusb_unlock_events() |
| * as soon as possible. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \ref libusb_mtasync |
| */ |
| void API_EXPORTED libusb_lock_events(libusb_context *ctx) |
| { |
| ctx = usbi_get_context(ctx); |
| usbi_mutex_lock(&ctx->events_lock); |
| ctx->event_handler_active = 1; |
| } |
| |
| /** \ingroup libusb_poll |
| * Release the lock previously acquired with libusb_try_lock_events() or |
| * libusb_lock_events(). Releasing this lock will wake up any threads blocked |
| * on libusb_wait_for_event(). |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \ref libusb_mtasync |
| */ |
| void API_EXPORTED libusb_unlock_events(libusb_context *ctx) |
| { |
| ctx = usbi_get_context(ctx); |
| ctx->event_handler_active = 0; |
| usbi_mutex_unlock(&ctx->events_lock); |
| |
| /* FIXME: perhaps we should be a bit more efficient by not broadcasting |
| * the availability of the events lock when we are modifying pollfds |
| * (check ctx->device_close)? */ |
| usbi_mutex_lock(&ctx->event_waiters_lock); |
| usbi_cond_broadcast(&ctx->event_waiters_cond); |
| usbi_mutex_unlock(&ctx->event_waiters_lock); |
| } |
| |
| /** \ingroup libusb_poll |
| * Determine if it is still OK for this thread to be doing event handling. |
| * |
| * Sometimes, libusb needs to temporarily pause all event handlers, and this |
| * is the function you should use before polling file descriptors to see if |
| * this is the case. |
| * |
| * If this function instructs your thread to give up the events lock, you |
| * should just continue the usual logic that is documented in \ref libusb_mtasync. |
| * On the next iteration, your thread will fail to obtain the events lock, |
| * and will hence become an event waiter. |
| * |
| * This function should be called while the events lock is held: you don't |
| * need to worry about the results of this function if your thread is not |
| * the current event handler. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \returns 1 if event handling can start or continue |
| * \returns 0 if this thread must give up the events lock |
| * \ref fullstory "Multi-threaded I/O: the full story" |
| */ |
| int API_EXPORTED libusb_event_handling_ok(libusb_context *ctx) |
| { |
| unsigned int r; |
| |
| ctx = usbi_get_context(ctx); |
| |
| /* is someone else waiting to close a device? if so, don't let this thread |
| * continue event handling */ |
| usbi_mutex_lock(&ctx->event_data_lock); |
| r = ctx->device_close; |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| if (r) { |
| usbi_dbg("someone else is closing a device"); |
| return 0; |
| } |
| |
| return 1; |
| } |
| |
| |
| /** \ingroup libusb_poll |
| * Determine if an active thread is handling events (i.e. if anyone is holding |
| * the event handling lock). |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \returns 1 if a thread is handling events |
| * \returns 0 if there are no threads currently handling events |
| * \ref libusb_mtasync |
| */ |
| int API_EXPORTED libusb_event_handler_active(libusb_context *ctx) |
| { |
| unsigned int r; |
| |
| ctx = usbi_get_context(ctx); |
| |
| /* is someone else waiting to close a device? if so, don't let this thread |
| * start event handling -- indicate that event handling is happening */ |
| usbi_mutex_lock(&ctx->event_data_lock); |
| r = ctx->device_close; |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| if (r) { |
| usbi_dbg("someone else is closing a device"); |
| return 1; |
| } |
| |
| return ctx->event_handler_active; |
| } |
| |
| /** \ingroup libusb_poll |
| * Interrupt any active thread that is handling events. This is mainly useful |
| * for interrupting a dedicated event handling thread when an application |
| * wishes to call libusb_exit(). |
| * |
| * Since version 1.0.21, \ref LIBUSB_API_VERSION >= 0x01000105 |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \ref libusb_mtasync |
| */ |
| void API_EXPORTED libusb_interrupt_event_handler(libusb_context *ctx) |
| { |
| unsigned int event_flags; |
| |
| usbi_dbg(" "); |
| |
| ctx = usbi_get_context(ctx); |
| usbi_mutex_lock(&ctx->event_data_lock); |
| |
| event_flags = ctx->event_flags; |
| ctx->event_flags |= USBI_EVENT_USER_INTERRUPT; |
| if (!event_flags) |
| usbi_signal_event(&ctx->event); |
| |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| } |
| |
| /** \ingroup libusb_poll |
| * Acquire the event waiters lock. This lock is designed to be obtained under |
| * the situation where you want to be aware when events are completed, but |
| * some other thread is event handling so calling libusb_handle_events() is not |
| * allowed. |
| * |
| * You then obtain this lock, re-check that another thread is still handling |
| * events, then call libusb_wait_for_event(). |
| * |
| * You only need to use this lock if you are developing an application |
| * which calls poll() or select() on libusb's file descriptors directly, |
| * <b>and</b> may potentially be handling events from 2 threads simultaneously. |
| * If you stick to libusb's event handling loop functions (e.g. |
| * libusb_handle_events()) then you do not need to be concerned with this |
| * locking. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \ref libusb_mtasync |
| */ |
| void API_EXPORTED libusb_lock_event_waiters(libusb_context *ctx) |
| { |
| ctx = usbi_get_context(ctx); |
| usbi_mutex_lock(&ctx->event_waiters_lock); |
| } |
| |
| /** \ingroup libusb_poll |
| * Release the event waiters lock. |
| * \param ctx the context to operate on, or NULL for the default context |
| * \ref libusb_mtasync |
| */ |
| void API_EXPORTED libusb_unlock_event_waiters(libusb_context *ctx) |
| { |
| ctx = usbi_get_context(ctx); |
| usbi_mutex_unlock(&ctx->event_waiters_lock); |
| } |
| |
| /** \ingroup libusb_poll |
| * Wait for another thread to signal completion of an event. Must be called |
| * with the event waiters lock held, see libusb_lock_event_waiters(). |
| * |
| * This function will block until any of the following conditions are met: |
| * -# The timeout expires |
| * -# A transfer completes |
| * -# A thread releases the event handling lock through libusb_unlock_events() |
| * |
| * Condition 1 is obvious. Condition 2 unblocks your thread <em>after</em> |
| * the callback for the transfer has completed. Condition 3 is important |
| * because it means that the thread that was previously handling events is no |
| * longer doing so, so if any events are to complete, another thread needs to |
| * step up and start event handling. |
| * |
| * This function releases the event waiters lock before putting your thread |
| * to sleep, and reacquires the lock as it is being woken up. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param tv maximum timeout for this blocking function. A NULL value |
| * indicates unlimited timeout. |
| * \returns 0 after a transfer completes or another thread stops event handling |
| * \returns 1 if the timeout expired |
| * \ref libusb_mtasync |
| */ |
| int API_EXPORTED libusb_wait_for_event(libusb_context *ctx, struct timeval *tv) |
| { |
| int r; |
| |
| ctx = usbi_get_context(ctx); |
| if (tv == NULL) { |
| usbi_cond_wait(&ctx->event_waiters_cond, &ctx->event_waiters_lock); |
| return 0; |
| } |
| |
| r = usbi_cond_timedwait(&ctx->event_waiters_cond, |
| &ctx->event_waiters_lock, tv); |
| |
| if (r < 0) |
| return r; |
| else |
| return (r == ETIMEDOUT); |
| } |
| |
| static void handle_timeout(struct usbi_transfer *itransfer) |
| { |
| struct libusb_transfer *transfer = |
| USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer); |
| int r; |
| |
| itransfer->timeout_flags |= USBI_TRANSFER_TIMEOUT_HANDLED; |
| r = libusb_cancel_transfer(transfer); |
| if (r == LIBUSB_SUCCESS) |
| itransfer->timeout_flags |= USBI_TRANSFER_TIMED_OUT; |
| else |
| usbi_warn(TRANSFER_CTX(transfer), |
| "async cancel failed %d errno=%d", r, errno); |
| } |
| |
| static int handle_timeouts_locked(struct libusb_context *ctx) |
| { |
| int r; |
| struct timespec systime; |
| struct usbi_transfer *itransfer; |
| |
| if (list_empty(&ctx->flying_transfers)) |
| return 0; |
| |
| /* get current time */ |
| r = usbi_clock_gettime(USBI_CLOCK_MONOTONIC, &systime); |
| if (r < 0) { |
| usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno); |
| return LIBUSB_ERROR_OTHER; |
| } |
| |
| /* iterate through flying transfers list, finding all transfers that |
| * have expired timeouts */ |
| for_each_transfer(ctx, itransfer) { |
| struct timespec *cur_ts = &itransfer->timeout; |
| |
| /* if we've reached transfers of infinite timeout, we're all done */ |
| if (!TIMESPEC_IS_SET(cur_ts)) |
| return 0; |
| |
| /* ignore timeouts we've already handled */ |
| if (itransfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT)) |
| continue; |
| |
| /* if transfer has non-expired timeout, nothing more to do */ |
| if (TIMESPEC_CMP(cur_ts, &systime, >)) |
| return 0; |
| |
| /* otherwise, we've got an expired timeout to handle */ |
| handle_timeout(itransfer); |
| } |
| return 0; |
| } |
| |
| static int handle_timeouts(struct libusb_context *ctx) |
| { |
| int r; |
| |
| ctx = usbi_get_context(ctx); |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| r = handle_timeouts_locked(ctx); |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| return r; |
| } |
| |
| static int handle_event_trigger(struct libusb_context *ctx) |
| { |
| struct list_head hotplug_msgs; |
| int r = 0; |
| |
| usbi_dbg("event triggered"); |
| |
| list_init(&hotplug_msgs); |
| |
| /* take the the event data lock while processing events */ |
| usbi_mutex_lock(&ctx->event_data_lock); |
| |
| /* check if someone modified the event sources */ |
| if (ctx->event_flags & USBI_EVENT_EVENT_SOURCES_MODIFIED) |
| usbi_dbg("someone updated the event sources"); |
| |
| if (ctx->event_flags & USBI_EVENT_USER_INTERRUPT) { |
| usbi_dbg("someone purposefully interrupted"); |
| ctx->event_flags &= ~USBI_EVENT_USER_INTERRUPT; |
| } |
| |
| /* check if someone is closing a device */ |
| if (ctx->event_flags & USBI_EVENT_DEVICE_CLOSE) |
| usbi_dbg("someone is closing a device"); |
| |
| /* check for any pending hotplug messages */ |
| if (ctx->event_flags & USBI_EVENT_HOTPLUG_MSG_PENDING) { |
| usbi_dbg("hotplug message received"); |
| ctx->event_flags &= ~USBI_EVENT_HOTPLUG_MSG_PENDING; |
| assert(!list_empty(&ctx->hotplug_msgs)); |
| list_cut(&hotplug_msgs, &ctx->hotplug_msgs); |
| } |
| |
| /* complete any pending transfers */ |
| if (ctx->event_flags & USBI_EVENT_TRANSFER_COMPLETED) { |
| assert(!list_empty(&ctx->completed_transfers)); |
| while (r == 0 && !list_empty(&ctx->completed_transfers)) { |
| struct usbi_transfer *itransfer = |
| list_first_entry(&ctx->completed_transfers, struct usbi_transfer, completed_list); |
| |
| list_del(&itransfer->completed_list); |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| r = usbi_backend.handle_transfer_completion(itransfer); |
| if (r) |
| usbi_err(ctx, "backend handle_transfer_completion failed with error %d", r); |
| usbi_mutex_lock(&ctx->event_data_lock); |
| } |
| |
| if (list_empty(&ctx->completed_transfers)) |
| ctx->event_flags &= ~USBI_EVENT_TRANSFER_COMPLETED; |
| } |
| |
| /* if no further pending events, clear the event */ |
| if (!ctx->event_flags) |
| usbi_clear_event(&ctx->event); |
| |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| |
| /* process the hotplug messages, if any */ |
| while (!list_empty(&hotplug_msgs)) { |
| struct libusb_hotplug_message *message = |
| list_first_entry(&hotplug_msgs, struct libusb_hotplug_message, list); |
| |
| usbi_hotplug_match(ctx, message->device, message->event); |
| |
| /* the device left, dereference the device */ |
| if (message->event == LIBUSB_HOTPLUG_EVENT_DEVICE_LEFT) |
| libusb_unref_device(message->device); |
| |
| list_del(&message->list); |
| free(message); |
| } |
| |
| return r; |
| } |
| |
| #ifdef HAVE_OS_TIMER |
| static int handle_timer_trigger(struct libusb_context *ctx) |
| { |
| int r; |
| |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| |
| /* process the timeout that just happened */ |
| r = handle_timeouts_locked(ctx); |
| if (r < 0) |
| goto out; |
| |
| /* arm for next timeout */ |
| r = arm_timer_for_next_timeout(ctx); |
| |
| out: |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| return r; |
| } |
| #endif |
| |
| /* do the actual event handling. assumes that no other thread is concurrently |
| * doing the same thing. */ |
| static int handle_events(struct libusb_context *ctx, struct timeval *tv) |
| { |
| struct usbi_reported_events reported_events; |
| int r, timeout_ms; |
| |
| /* prevent attempts to recursively handle events (e.g. calling into |
| * libusb_handle_events() from within a hotplug or transfer callback) */ |
| if (usbi_handling_events(ctx)) |
| return LIBUSB_ERROR_BUSY; |
| |
| /* only reallocate the event source data when the list of event sources has |
| * been modified since the last handle_events(), otherwise reuse them to |
| * save the additional overhead */ |
| usbi_mutex_lock(&ctx->event_data_lock); |
| if (ctx->event_flags & USBI_EVENT_EVENT_SOURCES_MODIFIED) { |
| usbi_dbg("event sources modified, reallocating event data"); |
| |
| /* free anything removed since we last ran */ |
| cleanup_removed_event_sources(ctx); |
| |
| r = usbi_alloc_event_data(ctx); |
| if (r) { |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| return r; |
| } |
| |
| /* reset the flag now that we have the updated list */ |
| ctx->event_flags &= ~USBI_EVENT_EVENT_SOURCES_MODIFIED; |
| |
| /* if no further pending events, clear the event so that we do |
| * not immediately return from the wait function */ |
| if (!ctx->event_flags) |
| usbi_clear_event(&ctx->event); |
| } |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| |
| timeout_ms = (int)(tv->tv_sec * 1000) + (tv->tv_usec / 1000); |
| |
| /* round up to next millisecond */ |
| if (tv->tv_usec % 1000) |
| timeout_ms++; |
| |
| usbi_start_event_handling(ctx); |
| |
| r = usbi_wait_for_events(ctx, &reported_events, timeout_ms); |
| if (r != LIBUSB_SUCCESS) { |
| if (r == LIBUSB_ERROR_TIMEOUT) |
| r = handle_timeouts(ctx); |
| goto done; |
| } |
| |
| if (reported_events.event_triggered) { |
| r = handle_event_trigger(ctx); |
| if (r) { |
| /* return error code */ |
| goto done; |
| } |
| } |
| |
| #ifdef HAVE_OS_TIMER |
| if (reported_events.timer_triggered) { |
| r = handle_timer_trigger(ctx); |
| if (r) { |
| /* return error code */ |
| goto done; |
| } |
| } |
| #endif |
| |
| if (!reported_events.num_ready) |
| goto done; |
| |
| r = usbi_backend.handle_events(ctx, reported_events.event_data, |
| reported_events.event_data_count, reported_events.num_ready); |
| if (r) |
| usbi_err(ctx, "backend handle_events failed with error %d", r); |
| |
| done: |
| usbi_end_event_handling(ctx); |
| return r; |
| } |
| |
| /* returns the smallest of: |
| * 1. timeout of next URB |
| * 2. user-supplied timeout |
| * returns 1 if there is an already-expired timeout, otherwise returns 0 |
| * and populates out |
| */ |
| static int get_next_timeout(libusb_context *ctx, struct timeval *tv, |
| struct timeval *out) |
| { |
| struct timeval timeout; |
| int r = libusb_get_next_timeout(ctx, &timeout); |
| if (r) { |
| /* timeout already expired? */ |
| if (!timerisset(&timeout)) |
| return 1; |
| |
| /* choose the smallest of next URB timeout or user specified timeout */ |
| if (timercmp(&timeout, tv, <)) |
| *out = timeout; |
| else |
| *out = *tv; |
| } else { |
| *out = *tv; |
| } |
| return 0; |
| } |
| |
| /** \ingroup libusb_poll |
| * Handle any pending events. |
| * |
| * libusb determines "pending events" by checking if any timeouts have expired |
| * and by checking the set of file descriptors for activity. |
| * |
| * If a zero timeval is passed, this function will handle any already-pending |
| * events and then immediately return in non-blocking style. |
| * |
| * If a non-zero timeval is passed and no events are currently pending, this |
| * function will block waiting for events to handle up until the specified |
| * timeout. If an event arrives or a signal is raised, this function will |
| * return early. |
| * |
| * If the parameter completed is not NULL then <em>after obtaining the event |
| * handling lock</em> this function will return immediately if the integer |
| * pointed to is not 0. This allows for race free waiting for the completion |
| * of a specific transfer. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param tv the maximum time to block waiting for events, or an all zero |
| * timeval struct for non-blocking mode |
| * \param completed pointer to completion integer to check, or NULL |
| * \returns 0 on success, or a LIBUSB_ERROR code on failure |
| * \ref libusb_mtasync |
| */ |
| int API_EXPORTED libusb_handle_events_timeout_completed(libusb_context *ctx, |
| struct timeval *tv, int *completed) |
| { |
| int r; |
| struct timeval poll_timeout; |
| |
| ctx = usbi_get_context(ctx); |
| r = get_next_timeout(ctx, tv, &poll_timeout); |
| if (r) { |
| /* timeout already expired */ |
| return handle_timeouts(ctx); |
| } |
| |
| retry: |
| if (libusb_try_lock_events(ctx) == 0) { |
| if (completed == NULL || !*completed) { |
| /* we obtained the event lock: do our own event handling */ |
| usbi_dbg("doing our own event handling"); |
| r = handle_events(ctx, &poll_timeout); |
| } |
| libusb_unlock_events(ctx); |
| return r; |
| } |
| |
| /* another thread is doing event handling. wait for thread events that |
| * notify event completion. */ |
| libusb_lock_event_waiters(ctx); |
| |
| if (completed && *completed) |
| goto already_done; |
| |
| if (!libusb_event_handler_active(ctx)) { |
| /* we hit a race: whoever was event handling earlier finished in the |
| * time it took us to reach this point. try the cycle again. */ |
| libusb_unlock_event_waiters(ctx); |
| usbi_dbg("event handler was active but went away, retrying"); |
| goto retry; |
| } |
| |
| usbi_dbg("another thread is doing event handling"); |
| r = libusb_wait_for_event(ctx, &poll_timeout); |
| |
| already_done: |
| libusb_unlock_event_waiters(ctx); |
| |
| if (r < 0) |
| return r; |
| else if (r == 1) |
| return handle_timeouts(ctx); |
| else |
| return 0; |
| } |
| |
| /** \ingroup libusb_poll |
| * Handle any pending events |
| * |
| * Like libusb_handle_events_timeout_completed(), but without the completed |
| * parameter, calling this function is equivalent to calling |
| * libusb_handle_events_timeout_completed() with a NULL completed parameter. |
| * |
| * This function is kept primarily for backwards compatibility. |
| * All new code should call libusb_handle_events_completed() or |
| * libusb_handle_events_timeout_completed() to avoid race conditions. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param tv the maximum time to block waiting for events, or an all zero |
| * timeval struct for non-blocking mode |
| * \returns 0 on success, or a LIBUSB_ERROR code on failure |
| */ |
| int API_EXPORTED libusb_handle_events_timeout(libusb_context *ctx, |
| struct timeval *tv) |
| { |
| return libusb_handle_events_timeout_completed(ctx, tv, NULL); |
| } |
| |
| /** \ingroup libusb_poll |
| * Handle any pending events in blocking mode. There is currently a timeout |
| * hard-coded at 60 seconds but we plan to make it unlimited in future. For |
| * finer control over whether this function is blocking or non-blocking, or |
| * for control over the timeout, use libusb_handle_events_timeout_completed() |
| * instead. |
| * |
| * This function is kept primarily for backwards compatibility. |
| * All new code should call libusb_handle_events_completed() or |
| * libusb_handle_events_timeout_completed() to avoid race conditions. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \returns 0 on success, or a LIBUSB_ERROR code on failure |
| */ |
| int API_EXPORTED libusb_handle_events(libusb_context *ctx) |
| { |
| struct timeval tv; |
| tv.tv_sec = 60; |
| tv.tv_usec = 0; |
| return libusb_handle_events_timeout_completed(ctx, &tv, NULL); |
| } |
| |
| /** \ingroup libusb_poll |
| * Handle any pending events in blocking mode. |
| * |
| * Like libusb_handle_events(), with the addition of a completed parameter |
| * to allow for race free waiting for the completion of a specific transfer. |
| * |
| * See libusb_handle_events_timeout_completed() for details on the completed |
| * parameter. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param completed pointer to completion integer to check, or NULL |
| * \returns 0 on success, or a LIBUSB_ERROR code on failure |
| * \ref libusb_mtasync |
| */ |
| int API_EXPORTED libusb_handle_events_completed(libusb_context *ctx, |
| int *completed) |
| { |
| struct timeval tv; |
| tv.tv_sec = 60; |
| tv.tv_usec = 0; |
| return libusb_handle_events_timeout_completed(ctx, &tv, completed); |
| } |
| |
| /** \ingroup libusb_poll |
| * Handle any pending events by polling file descriptors, without checking if |
| * any other threads are already doing so. Must be called with the event lock |
| * held, see libusb_lock_events(). |
| * |
| * This function is designed to be called under the situation where you have |
| * taken the event lock and are calling poll()/select() directly on libusb's |
| * file descriptors (as opposed to using libusb_handle_events() or similar). |
| * You detect events on libusb's descriptors, so you then call this function |
| * with a zero timeout value (while still holding the event lock). |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param tv the maximum time to block waiting for events, or zero for |
| * non-blocking mode |
| * \returns 0 on success, or a LIBUSB_ERROR code on failure |
| * \ref libusb_mtasync |
| */ |
| int API_EXPORTED libusb_handle_events_locked(libusb_context *ctx, |
| struct timeval *tv) |
| { |
| int r; |
| struct timeval poll_timeout; |
| |
| ctx = usbi_get_context(ctx); |
| r = get_next_timeout(ctx, tv, &poll_timeout); |
| if (r) { |
| /* timeout already expired */ |
| return handle_timeouts(ctx); |
| } |
| |
| return handle_events(ctx, &poll_timeout); |
| } |
| |
| /** \ingroup libusb_poll |
| * Determines whether your application must apply special timing considerations |
| * when monitoring libusb's file descriptors. |
| * |
| * This function is only useful for applications which retrieve and poll |
| * libusb's file descriptors in their own main loop (\ref libusb_pollmain). |
| * |
| * Ordinarily, libusb's event handler needs to be called into at specific |
| * moments in time (in addition to times when there is activity on the file |
| * descriptor set). The usual approach is to use libusb_get_next_timeout() |
| * to learn about when the next timeout occurs, and to adjust your |
| * poll()/select() timeout accordingly so that you can make a call into the |
| * library at that time. |
| * |
| * Some platforms supported by libusb do not come with this baggage - any |
| * events relevant to timing will be represented by activity on the file |
| * descriptor set, and libusb_get_next_timeout() will always return 0. |
| * This function allows you to detect whether you are running on such a |
| * platform. |
| * |
| * Since v1.0.5. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \returns 0 if you must call into libusb at times determined by |
| * libusb_get_next_timeout(), or 1 if all timeout events are handled internally |
| * or through regular activity on the file descriptors. |
| * \ref libusb_pollmain "Polling libusb file descriptors for event handling" |
| */ |
| int API_EXPORTED libusb_pollfds_handle_timeouts(libusb_context *ctx) |
| { |
| ctx = usbi_get_context(ctx); |
| return usbi_using_timer(ctx); |
| } |
| |
| /** \ingroup libusb_poll |
| * Determine the next internal timeout that libusb needs to handle. You only |
| * need to use this function if you are calling poll() or select() or similar |
| * on libusb's file descriptors yourself - you do not need to use it if you |
| * are calling libusb_handle_events() or a variant directly. |
| * |
| * You should call this function in your main loop in order to determine how |
| * long to wait for select() or poll() to return results. libusb needs to be |
| * called into at this timeout, so you should use it as an upper bound on |
| * your select() or poll() call. |
| * |
| * When the timeout has expired, call into libusb_handle_events_timeout() |
| * (perhaps in non-blocking mode) so that libusb can handle the timeout. |
| * |
| * This function may return 1 (success) and an all-zero timeval. If this is |
| * the case, it indicates that libusb has a timeout that has already expired |
| * so you should call libusb_handle_events_timeout() or similar immediately. |
| * A return code of 0 indicates that there are no pending timeouts. |
| * |
| * On some platforms, this function will always returns 0 (no pending |
| * timeouts). See \ref polltime. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param tv output location for a relative time against the current |
| * clock in which libusb must be called into in order to process timeout events |
| * \returns 0 if there are no pending timeouts, 1 if a timeout was returned, |
| * or LIBUSB_ERROR_OTHER on failure |
| */ |
| int API_EXPORTED libusb_get_next_timeout(libusb_context *ctx, |
| struct timeval *tv) |
| { |
| struct usbi_transfer *itransfer; |
| struct timespec systime; |
| struct timespec next_timeout = { 0, 0 }; |
| int r; |
| |
| ctx = usbi_get_context(ctx); |
| if (usbi_using_timer(ctx)) |
| return 0; |
| |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| if (list_empty(&ctx->flying_transfers)) { |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| usbi_dbg("no URBs, no timeout!"); |
| return 0; |
| } |
| |
| /* find next transfer which hasn't already been processed as timed out */ |
| for_each_transfer(ctx, itransfer) { |
| if (itransfer->timeout_flags & (USBI_TRANSFER_TIMEOUT_HANDLED | USBI_TRANSFER_OS_HANDLES_TIMEOUT)) |
| continue; |
| |
| /* if we've reached transfers of infinite timeout, we're done looking */ |
| if (!TIMESPEC_IS_SET(&itransfer->timeout)) |
| break; |
| |
| next_timeout = itransfer->timeout; |
| break; |
| } |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| |
| if (!TIMESPEC_IS_SET(&next_timeout)) { |
| usbi_dbg("no URB with timeout or all handled by OS; no timeout!"); |
| return 0; |
| } |
| |
| r = usbi_clock_gettime(USBI_CLOCK_MONOTONIC, &systime); |
| if (r < 0) { |
| usbi_err(ctx, "failed to read monotonic clock, errno=%d", errno); |
| return 0; |
| } |
| |
| if (!TIMESPEC_CMP(&systime, &next_timeout, <)) { |
| usbi_dbg("first timeout already expired"); |
| timerclear(tv); |
| } else { |
| TIMESPEC_SUB(&next_timeout, &systime, &next_timeout); |
| TIMESPEC_TO_TIMEVAL(tv, &next_timeout); |
| usbi_dbg("next timeout in %ld.%06lds", (long)tv->tv_sec, (long)tv->tv_usec); |
| } |
| |
| return 1; |
| } |
| |
| /** \ingroup libusb_poll |
| * Register notification functions for file descriptor additions/removals. |
| * These functions will be invoked for every new or removed file descriptor |
| * that libusb uses as an event source. |
| * |
| * To remove notifiers, pass NULL values for the function pointers. |
| * |
| * Note that file descriptors may have been added even before you register |
| * these notifiers (e.g. at libusb_init() time). |
| * |
| * Additionally, note that the removal notifier may be called during |
| * libusb_exit() (e.g. when it is closing file descriptors that were opened |
| * and added to the poll set at libusb_init() time). If you don't want this, |
| * remove the notifiers immediately before calling libusb_exit(). |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \param added_cb pointer to function for addition notifications |
| * \param removed_cb pointer to function for removal notifications |
| * \param user_data User data to be passed back to callbacks (useful for |
| * passing context information) |
| */ |
| void API_EXPORTED libusb_set_pollfd_notifiers(libusb_context *ctx, |
| libusb_pollfd_added_cb added_cb, libusb_pollfd_removed_cb removed_cb, |
| void *user_data) |
| { |
| #if !defined(_WIN32) && !defined(__CYGWIN__) |
| ctx = usbi_get_context(ctx); |
| ctx->fd_added_cb = added_cb; |
| ctx->fd_removed_cb = removed_cb; |
| ctx->fd_cb_user_data = user_data; |
| #else |
| usbi_err(ctx, "external polling of libusb's internal event sources " \ |
| "is not yet supported on Windows"); |
| UNUSED(added_cb); |
| UNUSED(removed_cb); |
| UNUSED(user_data); |
| #endif |
| } |
| |
| /* |
| * Interrupt the iteration of the event handling thread, so that it picks |
| * up the event source change. Callers of this function must hold the event_data_lock. |
| */ |
| static void usbi_event_source_notification(struct libusb_context *ctx) |
| { |
| unsigned int event_flags; |
| |
| /* Record that there is a new poll fd. |
| * Only signal an event if there are no prior pending events. */ |
| event_flags = ctx->event_flags; |
| ctx->event_flags |= USBI_EVENT_EVENT_SOURCES_MODIFIED; |
| if (!event_flags) |
| usbi_signal_event(&ctx->event); |
| } |
| |
| /* Add an event source to the list of event sources to be monitored. |
| * poll_events should be specified as a bitmask of events passed to poll(), e.g. |
| * POLLIN and/or POLLOUT. */ |
| int usbi_add_event_source(struct libusb_context *ctx, usbi_os_handle_t os_handle, short poll_events) |
| { |
| struct usbi_event_source *ievent_source = malloc(sizeof(*ievent_source)); |
| |
| if (!ievent_source) |
| return LIBUSB_ERROR_NO_MEM; |
| |
| usbi_dbg("add " USBI_OS_HANDLE_FORMAT_STRING " events %d", os_handle, poll_events); |
| ievent_source->data.os_handle = os_handle; |
| ievent_source->data.poll_events = poll_events; |
| usbi_mutex_lock(&ctx->event_data_lock); |
| list_add_tail(&ievent_source->list, &ctx->event_sources); |
| usbi_event_source_notification(ctx); |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| |
| #if !defined(_WIN32) && !defined(__CYGWIN__) |
| if (ctx->fd_added_cb) |
| ctx->fd_added_cb(os_handle, poll_events, ctx->fd_cb_user_data); |
| #endif |
| |
| return 0; |
| } |
| |
| /* Remove an event source from the list of event sources to be monitored. */ |
| void usbi_remove_event_source(struct libusb_context *ctx, usbi_os_handle_t os_handle) |
| { |
| struct usbi_event_source *ievent_source; |
| int found = 0; |
| |
| usbi_dbg("remove " USBI_OS_HANDLE_FORMAT_STRING, os_handle); |
| usbi_mutex_lock(&ctx->event_data_lock); |
| for_each_event_source(ctx, ievent_source) { |
| if (ievent_source->data.os_handle == os_handle) { |
| found = 1; |
| break; |
| } |
| } |
| |
| if (!found) { |
| usbi_dbg("couldn't find " USBI_OS_HANDLE_FORMAT_STRING " to remove", os_handle); |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| return; |
| } |
| |
| list_del(&ievent_source->list); |
| list_add_tail(&ievent_source->list, &ctx->removed_event_sources); |
| usbi_event_source_notification(ctx); |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| |
| #if !defined(_WIN32) && !defined(__CYGWIN__) |
| if (ctx->fd_removed_cb) |
| ctx->fd_removed_cb(os_handle, ctx->fd_cb_user_data); |
| #endif |
| } |
| |
| /** \ingroup libusb_poll |
| * Retrieve a list of file descriptors that should be polled by your main loop |
| * as libusb event sources. |
| * |
| * The returned list is NULL-terminated and should be freed with libusb_free_pollfds() |
| * when done. The actual list contents must not be touched. |
| * |
| * As file descriptors are a Unix-specific concept, this function is not |
| * available on Windows and will always return NULL. |
| * |
| * \param ctx the context to operate on, or NULL for the default context |
| * \returns a NULL-terminated list of libusb_pollfd structures |
| * \returns NULL on error |
| * \returns NULL on platforms where the functionality is not available |
| */ |
| DEFAULT_VISIBILITY |
| const struct libusb_pollfd ** LIBUSB_CALL libusb_get_pollfds( |
| libusb_context *ctx) |
| { |
| #if !defined(_WIN32) && !defined(__CYGWIN__) |
| struct libusb_pollfd **ret = NULL; |
| struct usbi_event_source *ievent_source; |
| size_t i; |
| |
| static_assert(sizeof(struct usbi_event_source_data) == sizeof(struct libusb_pollfd), |
| "mismatch between usbi_event_source_data and libusb_pollfd sizes"); |
| |
| ctx = usbi_get_context(ctx); |
| |
| usbi_mutex_lock(&ctx->event_data_lock); |
| |
| i = 0; |
| for_each_event_source(ctx, ievent_source) |
| i++; |
| |
| ret = calloc(i + 1, sizeof(struct libusb_pollfd *)); |
| if (!ret) |
| goto out; |
| |
| i = 0; |
| for_each_event_source(ctx, ievent_source) |
| ret[i++] = (struct libusb_pollfd *)ievent_source; |
| |
| out: |
| usbi_mutex_unlock(&ctx->event_data_lock); |
| return (const struct libusb_pollfd **)ret; |
| #else |
| usbi_err(ctx, "external polling of libusb's internal event sources " \ |
| "is not yet supported on Windows"); |
| return NULL; |
| #endif |
| } |
| |
| /** \ingroup libusb_poll |
| * Free a list of libusb_pollfd structures. This should be called for all |
| * pollfd lists allocated with libusb_get_pollfds(). |
| * |
| * Since version 1.0.20, \ref LIBUSB_API_VERSION >= 0x01000104 |
| * |
| * It is legal to call this function with a NULL pollfd list. In this case, |
| * the function will simply do nothing. |
| * |
| * \param pollfds the list of libusb_pollfd structures to free |
| */ |
| void API_EXPORTED libusb_free_pollfds(const struct libusb_pollfd **pollfds) |
| { |
| #if !defined(_WIN32) && !defined(__CYGWIN__) |
| free((void *)pollfds); |
| #else |
| UNUSED(pollfds); |
| #endif |
| } |
| |
| /* Backends may call this from handle_events to report disconnection of a |
| * device. This function ensures transfers get cancelled appropriately. |
| * Callers of this function must hold the events_lock. |
| */ |
| void usbi_handle_disconnect(struct libusb_device_handle *dev_handle) |
| { |
| struct libusb_context *ctx = HANDLE_CTX(dev_handle); |
| struct usbi_transfer *cur; |
| struct usbi_transfer *to_cancel; |
| |
| usbi_dbg("device %d.%d", |
| dev_handle->dev->bus_number, dev_handle->dev->device_address); |
| |
| /* terminate all pending transfers with the LIBUSB_TRANSFER_NO_DEVICE |
| * status code. |
| * |
| * when we find a transfer for this device on the list, there are two |
| * possible scenarios: |
| * 1. the transfer is currently in-flight, in which case we terminate the |
| * transfer here |
| * 2. the transfer has been added to the flying transfer list by |
| * libusb_submit_transfer, has failed to submit and |
| * libusb_submit_transfer is waiting for us to release the |
| * flying_transfers_lock to remove it, so we ignore it |
| */ |
| |
| while (1) { |
| to_cancel = NULL; |
| usbi_mutex_lock(&ctx->flying_transfers_lock); |
| for_each_transfer(ctx, cur) { |
| if (USBI_TRANSFER_TO_LIBUSB_TRANSFER(cur)->dev_handle == dev_handle) { |
| usbi_mutex_lock(&cur->lock); |
| if (cur->state_flags & USBI_TRANSFER_IN_FLIGHT) |
| to_cancel = cur; |
| usbi_mutex_unlock(&cur->lock); |
| |
| if (to_cancel) |
| break; |
| } |
| } |
| usbi_mutex_unlock(&ctx->flying_transfers_lock); |
| |
| if (!to_cancel) |
| break; |
| |
| usbi_dbg("cancelling transfer %p from disconnect", |
| USBI_TRANSFER_TO_LIBUSB_TRANSFER(to_cancel)); |
| |
| usbi_mutex_lock(&to_cancel->lock); |
| usbi_backend.clear_transfer_priv(to_cancel); |
| usbi_mutex_unlock(&to_cancel->lock); |
| usbi_handle_transfer_completion(to_cancel, LIBUSB_TRANSFER_NO_DEVICE); |
| } |
| } |