Hi Ricardo,
On Tue, Oct 08, 2024 at 07:06:14AM +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()")
Is this really the patch that introduced the problem?
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_video.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index cd9c29532fb0..853dfb7b5f7b 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -79,11 +79,16 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
> if (likely(ret == size))
> return 0;
>
> + if (ret > 0 && ret < size) {
> + memset(data + ret, 0, size - ret);
It'd be nice to have a comment in the code why this is being done
(including it's little endian).
> + return 0;
> + }
> +
> if (ret != -EPIPE) {
> dev_err(&dev->udev->dev,
> "Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",
> uvc_query_name(query), cs, unit, ret, size);
> - return ret < 0 ? ret : -EPIPE;
> + return ret ? ret : -EPIPE;
> }
>
> /* Reuse data[0] to request the error code. */
>
--
Kind regards,
Sakari Ailus
