linux_usbfs: Gracefully handle buggy devices with a configuration 0
The USB spec states that a configuration value of 0 is reserved and is
used to indicate the device in not configured (e.g. is in the address
state). Unfortunately some devices do exist that violate this and use 0
as the bConfigurationValue of the configuration descriptor.
Improve how the Linux backend handles such non-conformant devices by
adding special handling around the configuration value 0. Most devices
will not require this special handling, but for those that do there is
no way to distinguish between the device being unconfigured and using
configuration 0.
Closes #850
Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>
diff --git a/libusb/os/linux_usbfs.c b/libusb/os/linux_usbfs.c
index ebf8cfe..3a1894c 100644
--- a/libusb/os/linux_usbfs.c
+++ b/libusb/os/linux_usbfs.c
@@ -128,7 +128,7 @@
void *descriptors;
size_t descriptors_len;
struct config_descriptor *config_descriptors;
- uint8_t active_config; /* cache val for !sysfs_available */
+ int active_config; /* cache val for !sysfs_available */
};
struct linux_device_handle_priv {
@@ -169,6 +169,21 @@
int iso_packet_offset;
};
+static int dev_has_config0(struct libusb_device *dev)
+{
+ struct linux_device_priv *priv = usbi_get_device_priv(dev);
+ struct config_descriptor *config;
+ uint8_t idx;
+
+ for (idx = 0; idx < dev->device_descriptor.bNumConfigurations; idx++) {
+ config = &priv->config_descriptors[idx];
+ if (config->desc->bConfigurationValue == 0)
+ return 1;
+ }
+
+ return 0;
+}
+
static int get_usbfs_fd(struct libusb_device *dev, mode_t mode, int silent)
{
struct libusb_context *ctx = DEVICE_CTX(dev);
@@ -574,22 +589,12 @@
}
/* read the bConfigurationValue for a device */
-static int sysfs_get_active_config(struct libusb_device *dev, uint8_t *config)
+static int sysfs_get_active_config(struct libusb_device *dev, int *config)
{
struct linux_device_priv *priv = usbi_get_device_priv(dev);
- int ret, tmp;
- ret = read_sysfs_attr(DEVICE_CTX(dev), priv->sysfs_dir, "bConfigurationValue",
- UINT8_MAX, &tmp);
- if (ret < 0)
- return ret;
-
- if (tmp == -1)
- tmp = 0; /* unconfigured */
-
- *config = (uint8_t)tmp;
-
- return 0;
+ return read_sysfs_attr(DEVICE_CTX(dev), priv->sysfs_dir, "bConfigurationValue",
+ UINT8_MAX, config);
}
int linux_get_device_address(struct libusb_context *ctx, int detached,
@@ -765,6 +770,9 @@
}
}
+ if (config_desc->bConfigurationValue == 0)
+ usbi_warn(ctx, "device has configuration 0");
+
priv->config_descriptors[idx].desc = config_desc;
priv->config_descriptors[idx].actual_len = config_len;
@@ -798,7 +806,7 @@
{
struct linux_device_priv *priv = usbi_get_device_priv(dev);
void *config_desc;
- uint8_t active_config;
+ int active_config;
int r;
if (priv->sysfs_dir) {
@@ -810,12 +818,12 @@
active_config = priv->active_config;
}
- if (active_config == 0) {
+ if (active_config == -1) {
usbi_err(DEVICE_CTX(dev), "device unconfigured");
return LIBUSB_ERROR_NOT_FOUND;
}
- r = op_get_config_descriptor_by_value(dev, active_config, &config_desc);
+ r = op_get_config_descriptor_by_value(dev, (uint8_t)active_config, &config_desc);
if (r < 0)
return r;
@@ -863,16 +871,25 @@
/* we hit this error path frequently with buggy devices :( */
usbi_warn(DEVICE_CTX(dev), "get configuration failed, errno=%d", errno);
- } else if (active_config == 0) {
- /* some buggy devices have a configuration 0, but we're
- * reaching into the corner of a corner case here, so let's
- * not support buggy devices in these circumstances.
- * stick to the specs: a configuration value of 0 means
- * unconfigured. */
- usbi_warn(DEVICE_CTX(dev), "active cfg 0? assuming unconfigured device");
- }
- priv->active_config = active_config;
+ /* assume the current configuration is the first one if we have
+ * the configuration descriptors, otherwise treat the device
+ * as unconfigured. */
+ if (priv->config_descriptors)
+ priv->active_config = (int)priv->config_descriptors[0].desc->bConfigurationValue;
+ else
+ priv->active_config = -1;
+ } else if (active_config == 0) {
+ if (dev_has_config0(dev)) {
+ /* some buggy devices have a configuration 0, but we're
+ * reaching into the corner of a corner case here. */
+ priv->active_config = 0;
+ } else {
+ priv->active_config = -1;
+ }
+ } else {
+ priv->active_config = (int)active_config;
+ }
return LIBUSB_SUCCESS;
}
@@ -1004,9 +1021,9 @@
usbi_warn(ctx, "Missing rw usbfs access; cannot determine "
"active configuration descriptor");
if (priv->config_descriptors)
- priv->active_config = priv->config_descriptors[0].desc->bConfigurationValue;
+ priv->active_config = (int)priv->config_descriptors[0].desc->bConfigurationValue;
else
- priv->active_config = 0; /* No config dt */
+ priv->active_config = -1; /* No config dt */
return LIBUSB_SUCCESS;
}
@@ -1428,22 +1445,27 @@
uint8_t *config)
{
struct linux_device_priv *priv = usbi_get_device_priv(handle->dev);
+ int active_config;
int r;
if (priv->sysfs_dir) {
- r = sysfs_get_active_config(handle->dev, config);
+ r = sysfs_get_active_config(handle->dev, &active_config);
} else {
struct linux_device_handle_priv *hpriv = usbi_get_device_handle_priv(handle);
r = usbfs_get_active_config(handle->dev, hpriv->fd);
if (r == LIBUSB_SUCCESS)
- *config = priv->active_config;
+ active_config = priv->active_config;
}
if (r < 0)
return r;
- if (*config == 0)
- usbi_err(HANDLE_CTX(handle), "device unconfigured");
+ if (active_config == -1) {
+ usbi_warn(HANDLE_CTX(handle), "device unconfigured");
+ active_config = 0;
+ }
+
+ *config = (uint8_t)active_config;
return 0;
}
@@ -1467,11 +1489,13 @@
return LIBUSB_ERROR_OTHER;
}
- if (config == -1)
- config = 0;
+ /* if necessary, update our cached active config descriptor */
+ if (!priv->sysfs_dir) {
+ if (config == 0 && !dev_has_config0(handle->dev))
+ config = -1;
- /* update our cached active config descriptor */
- priv->active_config = (uint8_t)config;
+ priv->active_config = config;
+ }
return LIBUSB_SUCCESS;
}
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index e3bcede..db8faba 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11603
+#define LIBUSB_NANO 11604
