linux-kernel - Re: [PATCH RESEND v2 4/7] media: uvcvideo: Do not return positive errors in uvc_query

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Date:   Thu, 29 Dec 2022 05:28:32 +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>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Hans Verkuil <hans.verkuil@...co.com>
Subject: Re: [PATCH RESEND v2 4/7] media: uvcvideo: Do not return positive
 errors in uvc_query_ctrl()

Hi Ricardo,

Thank you for the patch.

On Fri, Dec 02, 2022 at 06:21:38PM +0100, Ricardo Ribalda wrote:
> If the returned size of the query does not match the expected size or it
> is zero, return -EPIPE instead of 0 or a positive value.

The commit message should explain why: this will avoid confusing the
caller (and ultimately userspace) that doesn't expect a positive or zero
value.

> Suggested-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>

I'll update the commit message locally.

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> ---
>  drivers/media/usb/uvc/uvc_video.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 497073a50194..902f2817a743 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -83,7 +83,7 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
>  		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;
> +		return ret < 0 ? ret : -EPIPE;
>  	}
>  
>  	/* reuse data[0] to request the error code. */
> 

-- 
Regards,

Laurent Pinchart