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media: uvcvideo: Support partial control reads 

Some cameras, like the ELMO MX-P3, do not return all the bytes
requested from a control if it can fit in less bytes.
Eg: Returning 0xab instead of 0x00ab.
usb 3-9: Failed to query (GET_DEF) UVC control 3 on unit 2: 1 (exp. 2).

Extend the returned value from the camera and return it.

Cc: stable@vger.kernel.org
Fixes: a763b9fb58 ("media: uvcvideo: Do not return positive errors in uvc_query_ctrl()")
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Link: https://lore.kernel.org/r/20241128-uvc-readless-v5-1-cf16ed282af8@chromium.org
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
pull/1134/merge
Ricardo Ribalda 2024-11-28 20:53:41 +00:00 committed by Mauro Carvalho Chehab
parent c31cffd5ae
commit f00ee2ca8d
1 changed files with 21 additions and 0 deletions
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21
drivers/media/usb/uvc/uvc_video.c
View File

@ -79,6 +79,27 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
if (likely(ret == size))
return 0;
/*
* Some devices return shorter USB control packets than expected if the
* returned value can fit in less bytes. Zero all the bytes that the
* device has not written.
*
* This quirk is applied to all controls, regardless of their data type.
* Most controls are little-endian integers, in which case the missing
* bytes become 0 MSBs. For other data types, a different heuristic
* could be implemented if a device is found needing it.
*
* We exclude UVC_GET_INFO from the quirk. UVC_GET_LEN does not need
* to be excluded because its size is always 1.
*/
if (ret > 0 && query != UVC_GET_INFO) {
memset(data + ret, 0, size - ret);
dev_warn_once(&dev->udev->dev,
"UVC non compliance: %s control %u on unit %u returned %d bytes when we expected %u.\n",
uvc_query_name(query), cs, unit, ret, size);
return 0;
}
if (ret != -EPIPE) {
dev_err(&dev->udev->dev,
"Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",