On Thu, Nov 28, 2024 at 08:53:41PM +0000, Ricardo Ribalda wrote:
> 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@xxxxxxxxxxxxxxx
> Fixes: a763b9fb58be ("media: uvcvideo: Do not return positive errors in uvc_query_ctrl()")
> Reviewed-by: Hans de Goede <hdegoede@xxxxxxxxxx>
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_video.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index cd9c29532fb0..67f714bca417 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -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",
--
Regards,
Laurent Pinchart
