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Subject: Re: a 4.16 kernel with Debian 9.4 "stretch" causes a log explosion
To: Guennadi Liakhovetski <g.liakhovetski@gmx.de>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Linux Media Mailing List <linux-media@vger.kernel.org>,
        Edgar Thier <info@edgarthier.net>
References: <alpine.DEB.2.20.1804110911021.18053@axis700.grange>
From: Kieran Bingham <kieran.bingham@ideasonboard.com>
Message-ID: <e79738af-8d6d-a6b1-2539-d2dbdb07bb53@ideasonboard.com>
Date: Wed, 11 Apr 2018 17:17:45 +0100
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Hi Guennadi,

On 11/04/18 10:56, Guennadi Liakhovetski wrote:
> Hi Laurent,
> 
> Not sure whether that's a kernel or a user-space problem, but UVC related 
> anyway. I've got a UVC 1.5 (!) Logitech camera, that used to work fine 
> with earlier kernels. I now installed "media 4.16" and saw, that the 
> kernel log was filling with messages like
> 
> uvcvideo: Failed to query (GET_MIN) UVC control 2 on unit 1: -32 (exp. 1).
> 
> The expected /dev/video[01] nodes were not created correctly, and the 
> hard-drive was getting full very quickly. The latter was happening because 
> the the /var/log/uvcdynctrl-udev.log file was growing. A truncated sample 
> is attached. At its bottom you see messages
> 
> [libwebcam] Warning: The driver behind device video0 has a slightly buggy implementation
>   of the V4L2_CTRL_FLAG_NEXT_CTRL flag. It does not return the next higher
>   control ID if a control query fails. A workaround has been enabled.
> 
> repeating, which continues even if the camera is unplugged. The kernel is 
> the head of the master branch of git://linuxtv.org/media_tree.git
> 
> Just figured out this commit
> 
> From: Edgar Thier <info@edgarthier.net>
> Date: Thu, 12 Oct 2017 03:54:17 -0400
> Subject: [PATCH] media: uvcvideo: Apply flags from device to actual properties
> 
> as the culprit. Without it everything is back to normal.

I've already investigated and fixed this:

Please apply:
	https://patchwork.kernel.org/patch/10299735/

You stated that this is showing up on a v4.16 kernel ... but as far as I'm aware
- this feature shouldn't make it in until v4.17. Are you using linux-next or a
media/master or such ?

Regards

Kieran

> Thanks
> Guennadi
>