On Tue, 26 Nov 2024 at 19:06, Laurent Pinchart
<laurent.pinchart@xxxxxxxxxxxxxxxx> wrote:
>
> On Wed, Nov 20, 2024 at 03:26:19PM +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>
> > ---
> > drivers/media/usb/uvc/uvc_video.c | 16 ++++++++++++++++
> > 1 file changed, 16 insertions(+)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index cd9c29532fb0..482c4ceceaac 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -79,6 +79,22 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
> > if (likely(ret == size))
> > return 0;
> >
> > + /*
> > + * In UVC the data is usually represented in little-endian.
>
> I had a comment about this in the previous version, did you ignore it on
> purpose because you disagreed, or was it an oversight ?
I rephrased the comment. I added "usually" to make it clear that it
might not be the case for all the data types. Like composed or xu.
I also r/package/packet/
Did I miss another comment?
>
> > + * Some devices return shorter USB control packets that expected if the
> > + * returned value can fit in less bytes. Zero all the bytes that the
> > + * device have not written.
>
> s/have/has/
>
> And if you meant to start a new paragraph here, a blank line is missing.
> Otherwise, no need to break the line before 80 columns.
The patch is already in the uvc tree. How do you want to handle this?
>
> > + * 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
--
Ricardo Ribalda
