Hi Herton,
On Wednesday 03 June 2009 23:02:33 Herton Ronaldo Krzesinski wrote:
> One webcam I have here exposes an invalid videostreaming interface
> format, with trace=0x2 this output is shown on kernel log:
>
> USB Video Class driver (v0.1.0)
> usb 3-7: new high speed USB device using ehci_hcd and address 5
> usb 3-7: configuration #1 chosen from 1 choice
> uvcvideo: Found format YUV 4:2:2 (YUYV).
> uvcvideo: - 640x480 (18.0 fps)
> uvcvideo: - 320x240 (30.0 fps)
> uvcvideo: - 160x120 (30.0 fps)
> uvcvideo: - 352x288 (30.0 fps)
> uvcvideo: - 176x144 (30.0 fps)
> uvcvideo: - 1280x1024 (8.0 fps)
> uvcvideo: device 5 videostreaminginterface 1 FORMAT error
> uvcvideo: Found a Status endpoint (addr 82).
> uvcvideo: Found UVC 1.00 device BisonCam, NB Pro (5986:0241)
> uvcvideo: No valid video chain found.
>
> There is an invalid videostreaming interface format exposed, which makes
> the webcam to fail to work as the error is treated as fatal, even if we
> have already found a valid format.
The invalid descriptor (I'm not sure if it's actually invalid, or just
vendor-specific and unsupported) isn't a Class Specific Interface descriptor
(bDescriptorType != 36), so it might make sense not to try to parse it instead
of trying and failing.
> Fix this by not failing entirely if we have found an invalid format, as
> we can still have a valid format. The initial problem and solution
> (patch) was debugged and done by Clevo (probably by Michael Wang),
> which uses the affected webcam in one of their laptops. I'm forwarding
> their fix plus additional code that I noticed to be needed for generic
> cases that decrements properly streaming->nformats and checks later if
> we really found at least one valid format, and if there were really no
> valid formats we make sure then to return with error.
What about modifying uvc_parse_streaming() to stop parsing the interface
descriptors when it encounters a non CS Interface descriptor instead ?
Something like
diff -r 66a270023c26 linux/drivers/media/video/uvc/uvc_driver.c
--- a/linux/drivers/media/video/uvc/uvc_driver.c Sun May 31 22:05:55
2009 +0200
+++ b/linux/drivers/media/video/uvc/uvc_driver.c Thu Jun 04 12:40:09
2009 +0200
@@ -644,7 +644,7 @@
_buflen = buflen;
/* Count the format and frame descriptors. */
- while (_buflen > 2) {
+ while (_buflen > 2 && _buffer[1] == CS_INTERFACE) {
switch (_buffer[2]) {
case VS_FORMAT_UNCOMPRESSED:
case VS_FORMAT_MJPEG:
@@ -709,7 +709,7 @@
streaming->nformats = nformats;
/* Parse the format descriptors. */
- while (buflen > 2) {
+ while (buflen > 2 && buffer[1] == CS_INTERFACE) {
switch (buffer[2]) {
case VS_FORMAT_UNCOMPRESSED:
case VS_FORMAT_MJPEG:
Best regards,
Laurent Pinchart
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