linux-kernel - Re: [PATCH v2 2/2] media: uvcvideo: Add more logging to uvc_query

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Message-ID: <CANiDSCu_-sy1XyEAPmoGELbzamO01UdA5-Dj0PCkOBeFUS2hbg@mail.gmail.com>
Date: Mon, 18 Nov 2024 18:16:31 +0100
From: Ricardo Ribalda <ribalda@...omium.org>
To: Hans de Goede <hdegoede@...hat.com>
Cc: Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
	Mauro Carvalho Chehab <mchehab@...nel.org>, linux-media@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH v2 2/2] media: uvcvideo: Add more logging to uvc_query_ctrl()

Hi Hans

On Mon, 18 Nov 2024 at 17:45, Hans de Goede <hdegoede@...hat.com> wrote:
>
> Hi Ricardo,
>
> Thank you for your patch.
>
> On 8-Oct-24 5:00 PM, Ricardo Ribalda wrote:
> > If we fail to query the ctrl error code there is no information on dmesg
> > or in uvc_dbg. This makes difficult to debug the issue.
> >
> > Print a proper error message when we cannot retrieve the error code from
> > the device.
> >
> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index f125b3ba50f2..6efbfa609059 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -111,8 +111,12 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
> >       error = *(u8 *)data;
> >       *(u8 *)data = tmp;
> >
> > -     if (ret != 1)
> > -             return ret < 0 ? ret : -EPIPE;
> > +     if (ret != 1) {
> > +             dev_err(&dev->udev->dev,
> > +                     "Failed to query (%s) UVC error code control %u on unit %u: %d (exp. 1).\n",
> > +                     uvc_query_name(query), cs, unit, ret);
> > +             return ret ? ret : -EPIPE;
>
> Adding error logging is always good, but again please drop the change
> to the return condition and stick with the:
>
>         return ret < 0 ? ret : -EPIPE;
>
> pattern used everywhere.
>
> Also in this case the return condition change really should have
> been in a separate patch since unlike before the success condition
> did not change, so it really is unrelated to adding the error
> logging.

It doesn't really change: __uvc_query_ctrl() in this case can return
1, 0 or a retval.
But I agree, the change does not provide anything (and I did not
mentioned it on the commit msg) let me restore the original return

Thanks

>
> Regards,
>
> Hans
>
>
>


-- 
Ricardo Ribalda