Hi Ricardo,
Thank you for the patch.
On Mon, Nov 18, 2024 at 05:16:51PM +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()")
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> drivers/media/usb/uvc/uvc_video.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index cd9c29532fb0..e165850397a0 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -76,8 +76,22 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
>
> ret = __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
> UVC_CTRL_CONTROL_TIMEOUT);
> - if (likely(ret == size))
> + if (ret > 0) {
> + if (size == ret)
> + return 0;
Why is this within the ret > 0 block ? I would write
if (likely(ret == size))
return 0;
if (ret > 0) {
> +
> + /*
> + * In UVC the data is represented in little-endian by default.
By default, or always ?
> + * Some devices return shorter control packages that expected
What's a "control package" ?
I think you meants "than expected", not "that expected".
> + * if the return value can fit in less bytes.
> + * Zero all the bytes that the device have not written.
> + */
Do we want to apply this workaround to GET_INFO and GET_LEN, or can we
restrict it to GET_CUR, GET_MIN, GET_MAX and GET_RES ?
> + 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,
>
--
Regards,
Laurent Pinchart
