linux-kernel - Re: [PATCH v3 2/8] media: uvcvideo: improve error logging in uvc_query

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Message-ID: <CANiDSCvgrScOzeCBmccC_SbGCZQp=dKbb43rQd=4L8oiHmRrvg@mail.gmail.com>
Date:   Tue, 3 Jan 2023 21:15:36 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Hans Verkuil <hans.verkuil@...co.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>
Subject: Re: [PATCH v3 2/8] media: uvcvideo: improve error logging in uvc_query_ctrl()

Hi Laurent

On Tue, 3 Jan 2023 at 21:13, Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
>
> On Tue, Jan 03, 2023 at 03:36:20PM +0100, Ricardo Ribalda wrote:
> > From: Hans Verkuil <hverkuil-cisco@...all.nl>
> >
> > Standard use of the driver may result in error messages on the kernel
> > ring buffer. This can hide other more important messages, and alert
>
> I assume you meant log (or log buffer), not ring buffer. I'll fix that
> when applying.

I tried to use the best term. And I found this:
https://man7.org/linux/man-pages/man1/dmesg.1.html

seems that kernel ring buffer is the correct term (but I might confess
that I use dmesg or simply log)

In this case, anything works for me ;)

Thanks!

>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
>
> > unnecessarily the user. Let's keep dev_err() for the important
> > occasions.
> >
> > If __uvc_query_ctrl() failed with a non -EPIPE error, then report that
> > with dev_err. If an error code is obtained, then report that with
> > dev_dbg.
> >
> > Reviewed-by: Ricardo Ribalda <ribalda@...omium.org>
> > Signed-off-by: Hans Verkuil <hans.verkuil@...co.com>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index d2eb9066e4dc..6b20a23bc3cf 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -79,13 +79,14 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
> >       if (likely(ret == size))
> >               return 0;
> >
> > -     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);
> > -
> > -     if (ret != -EPIPE)
> > +     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;
> > +     }
> >
> > +     /* Reuse data[0] to request the error code. */
> >       tmp = *(u8 *)data;
> >
> >       ret = __uvc_query_ctrl(dev, UVC_GET_CUR, 0, intfnum,
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda