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

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Message-ID: <Y7SMcMNwg1eflyCj@pendragon.ideasonboard.com>
Date:   Tue, 3 Jan 2023 22:13:36 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Ricardo Ribalda <ribalda@...omium.org>
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 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.

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