libusb/libusb.h

/*
 * Public libusb header file
 * Copyright (C) 2007-2008 Daniel Drake <dsd@gentoo.org>
 * Copyright (c) 2001 Johannes Erdfelt <johannes@erdfelt.com>
 *
 * 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
 */

#ifndef __LIBUSB_H__
#define __LIBUSB_H__

#include <stdint.h>
#include <sys/time.h>
#include <time.h>

#ifdef __cplusplus
extern "C" {
#endif

/* standard USB stuff */

/** \ingroup desc
 * Device and/or Interface Class codes */
enum libusb_class_code {
	/** In the context of a \ref libusb_device_descriptor "device descriptor",
	 * this bDeviceClass value indicates that each interface specifies its
	 * own class information and all interfaces operate independently.
	 */
	LIBUSB_CLASS_PER_INTERFACE = 0,

	/** Audio class */
	LIBUSB_CLASS_AUDIO = 1,

	/** Communications class */
	LIBUSB_CLASS_COMM = 2,

	/** Human Interface Device class */
	LIBUSB_CLASS_HID = 3,

	/** Printer dclass */
	LIBUSB_CLASS_PRINTER = 7,

	/** Picture transfer protocol class */
	LIBUSB_CLASS_PTP = 6,

	/** Mass storage class */
	LIBUSB_CLASS_MASS_STORAGE = 8,

	/** Hub class */
	LIBUSB_CLASS_HUB = 9,

	/** Data class */
	LIBUSB_CLASS_DATA = 10,

	/** Class is vendor-specific */
	LIBUSB_CLASS_VENDOR_SPEC = 0xff,
};

/** \ingroup desc
 * Descriptor types as defined by the USB specification. */
enum libusb_descriptor_type {
	/** Device descriptor. See libusb_device_descriptor. */
	LIBUSB_DT_DEVICE = 0x01,

	/** Configuration descriptor. See libusb_config_descriptor. */
	LIBUSB_DT_CONFIG = 0x02,

	/** String descriptor */
	LIBUSB_DT_STRING = 0x03,

	/** Interface descriptor. See libusb_interface_descriptor. */
	LIBUSB_DT_INTERFACE = 0x04,

	/** Endpoint descriptor. See libusb_endpoint_descriptor. */
	LIBUSB_DT_ENDPOINT = 0x05,

	/** HID descriptor */
	LIBUSB_DT_HID = 0x21,

	/** HID report descriptor */
	LIBUSB_DT_REPORT = 0x22,

	/** Physical descriptor */
	LIBUSB_DT_PHYSICAL = 0x23,

	/** Hub descriptor */
	LIBUSB_DT_HUB = 0x29,
};

/* Descriptor sizes per descriptor type */
#define LIBUSB_DT_DEVICE_SIZE			18
#define LIBUSB_DT_CONFIG_SIZE			9
#define LIBUSB_DT_INTERFACE_SIZE		9
#define LIBUSB_DT_ENDPOINT_SIZE		7
#define LIBUSB_DT_ENDPOINT_AUDIO_SIZE	9	/* Audio extension */
#define LIBUSB_DT_HUB_NONVAR_SIZE		7

#define LIBUSB_ENDPOINT_ADDRESS_MASK	0x0f    /* in bEndpointAddress */
#define LIBUSB_ENDPOINT_DIR_MASK		0x80

/** \ingroup desc
 * Endpoint direction. Values for bit 7 of the
 * \ref libusb_endpoint_descriptor::bEndpointAddress "endpoint address" scheme.
 */
enum libusb_endpoint_direction {
	/** In: device-to-host */
	LIBUSB_ENDPOINT_IN = 0x80,

	/** Out: host-to-device */
	LIBUSB_ENDPOINT_OUT = 0x00,
};

/* FIXME: 9.6.6 calls these "transfer types", not endpoint types. */
#define LIBUSB_ENDPOINT_TYPE_MASK			0x03    /* in bmAttributes */

/** \ingroup desc
 * Endpoint transfer type. Values for bits 0:1 of the
 * \ref libusb_endpoint_descriptor::bmAttributes "endpoint attributes" field.
 */
enum libusb_endpoint_type {
	/** Control endpoint */
	LIBUSB_ENDPOINT_TYPE_CONTROL = 0,

	/** Isochronous endpoint */
	LIBUSB_ENDPOINT_TYPE_ISOCHRONOUS = 1,

	/** Bulk endpoint */
	LIBUSB_ENDPOINT_TYPE_BULK = 2,

	/** Interrupt endpoint */
	LIBUSB_ENDPOINT_TYPE_INTERRUPT = 3,
};

/** Standard requests, as defined in table 9-3 of the USB2 specifications */
enum libusb_standard_request {
	/** Request status of the specific recipient */
	LIBUSB_REQUEST_GET_STATUS = 0x00,

	/** Clear or disable a specific feature */
	LIBUSB_REQUEST_CLEAR_FEATURE = 0x01,

	/* 0x02 is reserved */

	/** Set or enable a specific feature */
	LIBUSB_REQUEST_SET_FEATURE = 0x03,

	/* 0x04 is reserved */

	/** Set device address for all future accesses */
	LIBUSB_REQUEST_SET_ADDRESS = 0x05,

	/** Get the specified descriptor */
	LIBUSB_REQUEST_GET_DESCRIPTOR = 0x06,

	/** Used to update existing descriptors or add new descriptors */
	LIBUSB_REQUEST_SET_DESCRIPTOR = 0x07,

	/** Get the current device configuration value */
	LIBUSB_REQUEST_GET_CONFIGURATION = 0x08,

	/** Set device configuration */
	LIBUSB_REQUEST_SET_CONFIGURATION = 0x09,

	/** Return the selected alternate setting for the specified interface */
	LIBUSB_REQUEST_GET_INTERFACE = 0x0A,
	
	/** Select an alternate interface for the specified interface */
	LIBUSB_REQUEST_SET_INTERFACE = 0x0B,

	/** Set then report an endpoint's synchronization frame */
	LIBUSB_REQUEST_SYNCH_FRAME = 0x0C,
};

/** \ingroup misc
 * Request type bits of the
 * \ref libusb_control_setup::bmRequestType "bmRequestType" field in control
 * transfers. */
enum libusb_request_type {
	/** Standard */
	LIBUSB_REQUEST_TYPE_STANDARD = (0x00 << 5),

	/** Class */
	LIBUSB_REQUEST_TYPE_CLASS = (0x01 << 5),

	/** Vendor */
	LIBUSB_REQUEST_TYPE_VENDOR = (0x02 << 5),

	/** Reserved */
	LIBUSB_REQUEST_TYPE_RESERVED = (0x03 << 5),
};

/** \ingroup misc
 * Recipient bits of the
 * \ref libusb_control_setup::bmRequestType "bmRequestType" field in control
 * transfers. Values 4 through 31 are reserved. */
enum libusb_request_recipient {
	/** Device */
	LIBUSB_RECIPIENT_DEVICE = 0x00,

	/** Interface */
	LIBUSB_RECIPIENT_INTERFACE = 0x01,

	/** Endpoint */
	LIBUSB_RECIPIENT_ENDPOINT = 0x02,

	/** Other */
	LIBUSB_RECIPIENT_OTHER = 0x03,
};

#define LIBUSB_ISO_SYNC_TYPE_MASK		0x0C

/** \ingroup desc
 * Synchronization type for isochronous endpoints. Values for bits 2:3 of the
 * \ref libusb_endpoint_descriptor::bmAttributes "bmAttributes" field in
 * libusb_endpoint_descriptor.
 */
enum libusb_iso_sync_type {
	/** No synchronization */
	LIBUSB_ISO_SYNC_TYPE_NONE = 0,

	/** Asynchronous */
	LIBUSB_ISO_SYNC_TYPE_ASYNC = 1,

	/** Adaptive */
	LIBUSB_ISO_SYNC_TYPE_ADAPTIVE = 2,

	/** Synchronous */
	LIBUSB_ISO_SYNC_TYPE_SYNC = 3,
};

#define LIBUSB_ISO_USAGE_TYPE_MASK 0x30

/** \ingroup desc
 * Usage type for isochronous endpoints. Values for bits 4:5 of the
 * \ref libusb_endpoint_descriptor::bmAttributes "bmAttributes" field in
 * libusb_endpoint_descriptor.
 */
enum libusb_iso_usage_type {
	/** Data endpoint */
	LIBUSB_ISO_USAGE_TYPE_DATA = 0,

	/** Feedback endpoint */
	LIBUSB_ISO_USAGE_TYPE_FEEDBACK = 1,

	/** Implicit feedback Data endpoint */
	LIBUSB_ISO_USAGE_TYPE_IMPLICIT = 2,
};

/** \ingroup desc
 * A structure representing the standard USB device descriptor. This
 * descriptor is documented in section 9.6.1 of the USB 2.0 specification.
 * All multiple-byte fields are represented in host-endian format.
 */
struct libusb_device_descriptor {
	/** Size of this descriptor (in bytes) */
	uint8_t  bLength;

	/** Descriptor type. Will have value
	 * \ref libusb_descriptor_type::LIBUSB_DT_DEVICE LIBUSB_DT_DEVICE in this
	 * context. */
	uint8_t  bDescriptorType;

	/** USB specification release number in binary-coded decimal. A value of
	 * 0x0200 indicates USB 2.0, 0x0110 indicates USB 1.1, etc. */
	uint16_t bcdUSB;

	/** USB-IF class code for the device. See \ref libusb_class_code. */
	uint8_t  bDeviceClass;

	/** USB-IF subclass code for the device, qualified by the bDeviceClass
	 * value */
	uint8_t  bDeviceSubClass;

	/** USB-IF protocol code for the device, qualified by the bDeviceClass and
	 * bDeviceSubClass values */
	uint8_t  bDeviceProtocol;

	/** Maximum packet size for endpoint 0 */
	uint8_t  bMaxPacketSize0;

	/** USB-IF vendor ID */
	uint16_t idVendor;

	/** USB-IF product ID */
	uint16_t idProduct;

	/** Device release number in binary-coded decimal */
	uint16_t bcdDevice;

	/** Index of string descriptor describing manufacturer */
	uint8_t  iManufacturer;

	/** Index of string descriptor describing product */
	uint8_t  iProduct;

	/** Index of string descriptor containing device serial number */
	uint8_t  iSerialNumber;

	/** Number of possible configurations */
	uint8_t  bNumConfigurations;
};

/** \ingroup desc
 * A structure representing the standard USB endpoint descriptor. This
 * descriptor is documented in section 9.6.3 of the USB 2.0 specification.
 * All multiple-byte fields are represented in host-endian format.
 */
struct libusb_endpoint_descriptor {
	/** Size of this descriptor (in bytes) */
	uint8_t  bLength;

	/** Descriptor type. Will have value
	 * \ref libusb_descriptor_type::LIBUSB_DT_ENDPOINT LIBUSB_DT_ENDPOINT in
	 * this context. */
	uint8_t  bDescriptorType;

	/** The address of the endpoint described by this descriptor. Bits 0:3 are
	 * the endpoint number. Bits 4:6 are reserved. Bit 7 indicates direction,
	 * see \ref libusb_endpoint_direction.
	 */
	uint8_t  bEndpointAddress;

	/** Attributes which apply to the endpoint when it is configured using
	 * the bConfigurationValue. Bits 0:1 determine the transfer type and
	 * correspond to \ref libusb_endpoint_type. Bits 2:3 are only used for
	 * isochronous endpoints and correspond to \ref libusb_iso_sync_type.
	 * Bits 4:5 are also only used for isochronous endpoints and correspond to
	 * \ref libusb_iso_usage_type. Bits 6:7 are reserved.
	 */
	uint8_t  bmAttributes;

	/** Maximum packet size this endpoint is capable of sending/receiving. */
	uint16_t wMaxPacketSize;

	/** Interval for polling endpoint for data transfers. */
	uint8_t  bInterval;

	uint8_t  bRefresh;
	uint8_t  bSynchAddress;

	const unsigned char *extra;	/* Extra descriptors */
	int extralen;
};

/** \ingroup desc
 * A structure representing the standard USB interface descriptor. This
 * descriptor is documented in section 9.6.5 of the USB 2.0 specification.
 * All multiple-byte fields are represented in host-endian format.
 */
struct libusb_interface_descriptor {
	/** Size of this descriptor (in bytes) */
	uint8_t  bLength;

	/** Descriptor type. Will have value
	 * \ref libusb_descriptor_type::LIBUSB_DT_INTERFACE LIBUSB_DT_INTERFACE
	 * in this context. */
	uint8_t  bDescriptorType;

	/** Number of this interface */
	uint8_t  bInterfaceNumber;

	/** Value used to select this alternate setting for this interface */
	uint8_t  bAlternateSetting;

	/** Number of endpoints used by this interface (excluding the control
	 * endpoint). */
	uint8_t  bNumEndpoints;
	
	/** USB-IF class code for this interface. See \ref libusb_class_code. */
	uint8_t  bInterfaceClass;

	/** USB-IF subclass code for this interface, qualified by the
	 * bInterfaceClass value */
	uint8_t  bInterfaceSubClass;

	/** USB-IF protocol code for this interface, qualified by the
	 * bInterfaceClass and bInterfaceSubClass values */
	uint8_t  bInterfaceProtocol;

	/** Index of string descriptor describing this interface */
	uint8_t  iInterface;

	/** Array of endpoint descriptors. This length of this array is determined
	 * by the bNumEndpoints field. */
	const struct libusb_endpoint_descriptor *endpoint;

	const unsigned char *extra;	/* Extra descriptors */
	int extralen;
};

/** \ingroup desc
 * A collection of alternate settings for a particular USB interface.
 */
struct libusb_interface {
	/** Array of interface descriptors. The length of this array is determined
	 * by the num_altsetting field. */
	const struct libusb_interface_descriptor *altsetting;

	/** The number of alternate settings that belong to this interface */
	int num_altsetting;
};

/** \ingroup desc
 * A structure representing the standard USB configuration descriptor. This
 * descriptor is documented in section 9.6.3 of the USB 2.0 specification.
 * All multiple-byte fields are represented in host-endian format.
 */
struct libusb_config_descriptor {
	/** Size of this descriptor (in bytes) */
	uint8_t  bLength;

	/** Descriptor type. Will have value
	 * \ref libusb_descriptor_type::LIBUSB_DT_CONFIG LIBUSB_DT_CONFIG
	 * in this context. */
	uint8_t  bDescriptorType;

	/** Total length of data returned for this configuration */
	uint16_t wTotalLength;

	/** Number of interfaces supported by this configuration */
	uint8_t  bNumInterfaces;

	/** Identifier value for this configuration */
	uint8_t  bConfigurationValue;

	/** Index of string descriptor describing this configuration */
	uint8_t  iConfiguration;

	/** Configuration characteristics */
	uint8_t  bmAttributes;

	/** Maximum power consumption of the USB device from this bus in this
	 * configuration when the device is fully opreation. Expressed in units
	 * of 2 mA. */
	uint8_t  MaxPower;

	/** Array of interfaces supported by this configuration. The length of
	 * this array is determined by the bNumInterfaces field. */
	const struct libusb_interface *interface;

	const unsigned char *extra;	/* Extra descriptors */
	int extralen;
};

/** \ingroup asyncio
 * Setup packet for control transfers. */
struct libusb_control_setup {
	/** Request type. Bits 0:4 determine recipient, see
	 * \ref libusb_request_recipient. Bits 5:6 determine type, see
	 * \ref libusb_request_type. Bit 7 determines data transfer direction, see
	 * \ref libusb_endpoint_direction.
	 */
	uint8_t  bmRequestType;

	/** Request. If the type bits of bmRequestType are equal to
	 * \ref libusb_request_type::LIBUSB_REQUEST_TYPE_STANDARD
	 * "LIBUSB_REQUEST_TYPE_STANDARD" then this field refers to
	 * \ref libusb_standard_request. For other cases, use of this field is
	 * application-specific. */
	uint8_t  bRequest;

	/** Value. Varies according to request */
	uint16_t wValue;

	/** Index. Varies according to request, typically used to pass an index
	 * or offset */
	uint16_t wIndex;

	/** Number of bytes to transfer */
	uint16_t wLength;
} __attribute__((packed));

#define LIBUSB_CONTROL_SETUP_SIZE (sizeof(struct libusb_control_setup))

/* libusb */

struct libusb_device;
typedef struct libusb_device libusb_device;

struct libusb_device_handle;
typedef struct libusb_device_handle libusb_device_handle;

/** \ingroup asyncio
 * Transfer status codes */
enum libusb_transfer_status {
	/** Transfer completed without error. Note that this does not indicate
	 * that the entire amount of requested data was transferred. */
	LIBUSB_TRANSFER_COMPLETED,

	/** Transfer failed */
	LIBUSB_TRANSFER_ERROR,

	/** Transfer timed out */
	LIBUSB_TRANSFER_TIMED_OUT,

	/** Transfer was cancelled */
	LIBUSB_TRANSFER_CANCELLED,
};

/** \ingroup asyncio
 * libusb_transfer.flags values */
enum libusb_transfer_flags {
	/** Report short frames as errors */
	LIBUSB_TRANSFER_SHORT_NOT_OK = 1<<0,

	/** Automatically free() transfer buffer during libusb_free_transfer() */
	LIBUSB_TRANSFER_FREE_BUFFER = 1<<1,

	/** Automatically call libusb_free_transfer() after callback returns.
	 * If this flag is set, it is illegal to call libusb_free_transfer() 
	 * from your transfer callback, as this will result in a double-free
	 * when this flag is acted upon. */
	LIBUSB_TRANSFER_FREE_TRANSFER = 1<<2,
};

/** \ingroup asyncio
 * Isochronous packet descriptor. */
struct libusb_iso_packet_descriptor {
	/** Length of data to request in this packet */
	unsigned int length;

	/** Amount of data that was actually transferred */
	unsigned int actual_length;

	/** Status code for this packet */
	enum libusb_transfer_status status;
};

struct libusb_transfer;

typedef void (*libusb_transfer_cb_fn)(struct libusb_transfer *transfer);

/** \ingroup asyncio
 * The generic USB transfer structure.
 */
struct libusb_transfer {
	/** Handle of the device that this transfer will be submitted to */
	libusb_device_handle *dev_handle;

	/** A bitwise OR combination of \ref libusb_transfer_flags. */
	uint8_t flags;

	/** Address of the endpoint where this transfer will be sent. */
	unsigned char endpoint;

	/** Type of the endpoint from \ref libusb_endpoint_type */
	unsigned char endpoint_type;

	/** Timeout for this transfer in millseconds. A value of 0 indicates no
	 * timeout. */
	unsigned int timeout;

	/* FIXME: make const? */
	/** The status of the transfer. Read-only, and only for use within
	 * transfer callback function.
	 *
	 * If this is an isochronous transfer, this field may read COMPLETED even
	 * if there were errors in the frames. Use the
	 * \ref libusb_iso_packet_descriptor::status "status" field in each packet
	 * to determine if errors occurred. */
	enum libusb_transfer_status status;

	/** Length of the data buffer */
	int length;

	/** Actual length of data that was transferred. Read-only, and only for
	 * use within transfer callback function. Not valid for isochronous
	 * endpoint transfers. */
	int actual_length;

	/** Callback function. This will be invoked when the transfer completes,
	 * fails, or is cancelled. */
	libusb_transfer_cb_fn callback;

	/** User context data to pass to the callback function. */
	void *user_data;

	/** Data buffer */
	unsigned char *buffer;

	/** Number of isochronous packets. Only used for I/O with isochronous
	 * endpoints. */
	int num_iso_packets;

	/** Isochronous packet descriptors, for isochronous transfers only. */
	struct libusb_iso_packet_descriptor iso_packet_desc[0];
};

int libusb_init(void);
void libusb_exit(void);

int libusb_get_device_list(libusb_device ***list);
void libusb_free_device_list(libusb_device **list, int unref_devices);
const struct libusb_device_descriptor *libusb_get_device_descriptor(
	libusb_device *dev);
const struct libusb_config_descriptor *libusb_get_config_descriptor(
	libusb_device *dev);
libusb_device *libusb_device_ref(libusb_device *dev);
void libusb_device_unref(libusb_device *dev);

libusb_device_handle *libusb_open(libusb_device *dev);
void libusb_close(libusb_device_handle *dev_handle);
libusb_device *libusb_get_device(libusb_device_handle *dev_handle);
int libusb_claim_interface(libusb_device_handle *dev, int iface);
int libusb_release_interface(libusb_device_handle *dev, int iface);

libusb_device_handle *libusb_open_device_with_vid_pid(uint16_t vendor_id,
	uint16_t product_id);

int libusb_set_interface_altsetting(libusb_device_handle *dev, int iface,
	int altsetting);

/* async I/O */

/** \ingroup asyncio
 * Get the data section of a control transfer. This convenience function is here
 * to remind you that the data does not start until 8 bytes into the actual
 * buffer, as the setup packet comes first. 
 *
 * Calling this function only makes sense from a transfer callback function,
 * or situations where you have already allocated a suitably sized buffer at
 * transfer->buffer.
 *
 * \param transfer a transfer
 * \returns pointer to the first byte of the data section
 */
static inline unsigned char *libusb_control_transfer_get_data(
	struct libusb_transfer *transfer)
{
	return transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
}

/** \ingroup asyncio
 * Get the control setup packet of a control transfer. This convenience
 * function is here to remind you that the control setup occupies the first
 * 8 bytes of the transfer data buffer.
 *
 * Calling this function only makes sense from a transfer callback function,
 * or situations where you have already allocated a suitably sized buffer at
 * transfer->buffer.
 *
 * \param transfer a transfer
 * \returns a casted pointer to the start of the transfer data buffer
 */
static inline struct libusb_control_setup *libusb_control_transfer_get_setup(
	struct libusb_transfer *transfer)
{
	return (struct libusb_control_setup *) transfer->buffer;
}

/** \ingroup asyncio
 * Helper function to populate the setup packet (first 8 bytes of the data
 * buffer) for a control transfer.
 * 
 * \param buffer buffer to output the setup packet into
 * \param bmRequestType see the
 * \ref libusb_control_setup::bmRequestType "bmRequestType" field of
 * \ref libusb_control_setup
 * \param bRequest see the
 * \ref libusb_control_setup::bRequest "bRequest" field of 
 * \ref libusb_control_setup
 * \param wValue see the
 * \ref libusb_control_setup::wValue "wValue" field of 
 * \ref libusb_control_setup
 * \param wIndex see the
 * \ref libusb_control_setup::wIndex "wIndex" field of 
 * \ref libusb_control_setup
 * \param wLength see the
 * \ref libusb_control_setup::wLength "wLength" field of 
 * \ref libusb_control_setup
 */
static inline void libusb_fill_control_setup(unsigned char *buffer,
	uint8_t bmRequestType, uint8_t bRequest, uint16_t wValue, uint16_t wIndex,
	uint16_t wLength)
{
	struct libusb_control_setup *setup = (struct libusb_control_setup *) buffer;
	setup->bmRequestType = bmRequestType;
	setup->bRequest = bRequest;
	setup->wValue = wValue;
	setup->wIndex = wIndex;
	setup->wLength = wLength;
}

size_t libusb_get_transfer_alloc_size(void);
void libusb_init_transfer(struct libusb_transfer *transfer);

struct libusb_transfer *libusb_alloc_transfer(int iso_packets);
int libusb_submit_transfer(struct libusb_transfer *transfer);
int libusb_cancel_transfer(struct libusb_transfer *transfer);
void libusb_free_transfer(struct libusb_transfer *transfer);

/** \ingroup asyncio
 * Helper function to populate the required \ref libusb_transfer fields
 * for a control transfer.
 *
 * If you pass a transfer buffer to this function, the first 8 bytes will
 * be interpreted as a control setup packet, and the wLength field will be
 * used to automatically populate the \ref libusb_transfer::length "length"
 * field of the transfer. Therefore the recommended approach is:
 * -# Allocate a suitably sized data buffer (including space for control setup)
 * -# Call libusb_fill_control_setup()
 * -# If this is a host-to-device transfer with a data stage, put the data
 *    in place after the setup packet
 * -# Call this function
 * -# Call libusb_submit_transfer()
 *
 * It is also legal to pass a NULL buffer to this function, in which case this
 * function will not attempt to populate the length field. Remember that you
 * must populate the buffer and length fields later.
 *
 * \param transfer the transfer to populate
 * \param dev_handle handle of the device that will handle the transfer
 * \param buffer data buffer. If provided, this function will interpret the
 * first 8 bytes as a setup packet and infer the transfer length from that.
 * \param callback callback function to be invoked on transfer completion
 * \param user_data user data to pass to callback function
 * \param timeout timeout for the transfer in milliseconds
 */
static inline void libusb_fill_control_transfer(
	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
	unsigned char *buffer, libusb_transfer_cb_fn callback, void *user_data,
	unsigned int timeout)
{
	struct libusb_control_setup *setup = (struct libusb_control_setup *) buffer;
	transfer->dev_handle = dev_handle;
	transfer->endpoint = 0;
	transfer->endpoint_type = LIBUSB_ENDPOINT_TYPE_CONTROL;
	transfer->timeout = timeout;
	transfer->buffer = buffer;
	if (setup)
		transfer->length = LIBUSB_CONTROL_SETUP_SIZE + setup->wLength;
	transfer->user_data = user_data;
	transfer->callback = callback;
}

/** \ingroup asyncio
 * Helper function to populate the required \ref libusb_transfer fields
 * for a bulk transfer.
 *
 * \param transfer the transfer to populate
 * \param dev_handle handle of the device that will handle the transfer
 * \param endpoint address of the endpoint where this transfer will be sent
 * \param buffer data buffer
 * \param length length of data buffer
 * \param callback callback function to be invoked on transfer completion
 * \param user_data user data to pass to callback function
 * \param timeout timeout for the transfer in milliseconds
 */
static inline void libusb_fill_bulk_transfer(struct libusb_transfer *transfer,
	libusb_device_handle *dev_handle, unsigned char endpoint,
	unsigned char *buffer, int length, libusb_transfer_cb_fn callback,
	void *user_data, unsigned int timeout)
{
	transfer->dev_handle = dev_handle;
	transfer->endpoint = endpoint;
	transfer->endpoint_type = LIBUSB_ENDPOINT_TYPE_BULK;
	transfer->timeout = timeout;
	transfer->buffer = buffer;
	transfer->length = length;
	transfer->user_data = user_data;
	transfer->callback = callback;
}

/** \ingroup asyncio
 * Helper function to populate the required \ref libusb_transfer fields
 * for an interrupt transfer.
 *
 * \param transfer the transfer to populate
 * \param dev_handle handle of the device that will handle the transfer
 * \param endpoint address of the endpoint where this transfer will be sent
 * \param buffer data buffer
 * \param length length of data buffer
 * \param callback callback function to be invoked on transfer completion
 * \param user_data user data to pass to callback function
 * \param timeout timeout for the transfer in milliseconds
 */
static inline void libusb_fill_interrupt_transfer(
	struct libusb_transfer *transfer, libusb_device_handle *dev_handle,
	unsigned char endpoint, unsigned char *buffer, int length,
	libusb_transfer_cb_fn callback, void *user_data, unsigned int timeout)
{
	transfer->dev_handle = dev_handle;
	transfer->endpoint = endpoint;
	transfer->endpoint_type = LIBUSB_ENDPOINT_TYPE_INTERRUPT;
	transfer->timeout = timeout;
	transfer->buffer = buffer;
	transfer->length = length;
	transfer->user_data = user_data;
	transfer->callback = callback;
}

/** \ingroup asyncio
 * Helper function to populate the required \ref libusb_transfer fields
 * for an isochronous transfer.
 *
 * \param transfer the transfer to populate
 * \param dev_handle handle of the device that will handle the transfer
 * \param endpoint address of the endpoint where this transfer will be sent
 * \param buffer data buffer
 * \param length length of data buffer
 * \param num_iso_packets the number of isochronous packets
 * \param callback callback function to be invoked on transfer completion
 * \param user_data user data to pass to callback function
 * \param timeout timeout for the transfer in milliseconds
 */
static inline void libusb_fill_iso_transfer(struct libusb_transfer *transfer,
	libusb_device_handle *dev_handle, unsigned char endpoint,
	unsigned char *buffer, int length, int num_iso_packets,
	libusb_transfer_cb_fn callback, void *user_data, unsigned int timeout)
{
	transfer->dev_handle = dev_handle;
	transfer->endpoint = endpoint;
	transfer->endpoint_type = LIBUSB_ENDPOINT_TYPE_ISOCHRONOUS;
	transfer->timeout = timeout;
	transfer->buffer = buffer;
	transfer->length = length;
	transfer->num_iso_packets = num_iso_packets;
	transfer->user_data = user_data;
	transfer->callback = callback;
}

/* sync I/O */

int libusb_control_transfer(libusb_device_handle *dev_handle,
	uint8_t request_type, uint8_t request, uint16_t value, uint16_t index,
	unsigned char *data, uint16_t length, unsigned int timeout);

int libusb_bulk_transfer(libusb_device_handle *dev_handle,
	unsigned char endpoint, unsigned char *data, int length,
	int *actual_length, unsigned int timeout);

int libusb_interrupt_transfer(libusb_device_handle *dev_handle,
	unsigned char endpoint, unsigned char *data, int length,
	int *actual_length, unsigned int timeout);

/* polling and timeouts */

/** \ingroup poll
 * File descriptor for polling
 */
struct libusb_pollfd {
	/** Numeric file descriptor */
	int fd;

	/** Event flags to poll for from <poll.h>. POLLIN indicates that you
	 * should monitor this file descriptor for becoming ready to read from,
	 * and POLLOUT indicates that you should monitor this file descriptor for
	 * nonblocking write readiness. */
	short events;
};

int libusb_handle_events_timeout(struct timeval *tv);
int libusb_handle_events(void);
int libusb_get_next_timeout(struct timeval *tv);
const struct libusb_pollfd **libusb_get_pollfds(void);

typedef void (*libusb_pollfd_added_cb)(int fd, short events);
typedef void (*libusb_pollfd_removed_cb)(int fd);
void libusb_set_pollfd_notifiers(libusb_pollfd_added_cb added_cb,
	libusb_pollfd_removed_cb removed_cb);

#ifdef __cplusplus
}
#endif

#endif