linux-kernel - Re: 2.6.28 changes in-kernel name for UVC device ?

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Message-ID: <49760649.8000800@s5r6.in-berlin.de>
Date:	Tue, 20 Jan 2009 18:13:45 +0100
From:	Stefan Richter <stefanr@...6.in-berlin.de>
To:	Kay Sievers <kay.sievers@...y.org>
CC:	Ionut Leonte <ionut.leonte@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: 2.6.28 changes in-kernel name for UVC device ?

Kay Sievers wrote:
> On Tue, Jan 20, 2009 at 12:49, Ionut Leonte <ionut.leonte@...il.com> wrote:
>> I have a Dell laptop with an integrated webcam which works with the 'uvcvideo'
>> module. For kernel versions 2.6.27 and below the following udev rule:
>>
>>   KERNEL=="video[0-9]*",  NAME="v4l/video%n", SYMLINK+="%k", GROUP="video"
>>
>> would create '/dev/video0' as a link to '/dev/v4l/video0'. When switching to
>> 2.6.28 the rule creates '/dev/video1394-0' instead. Obviously most user-space
>> apps were quite surprised by this (as was I).
>>
>> Is this change intended or is it the accidental result of some modification ?
> 
> These rules are broken, and match also on firewire devices and not
> only video4linux devices.
> 
> Such rules are not part of the standard udev setup and need to be
> fixed to work as intended. There is no change or fault at the kernel
> side.

Exactly.

> You may just disable the firefire drivers if you don't need them.

It is not even necessary to disable the drivers; it would be sufficient
to not force-load the video1394 module.  (Or to fix the udev rule.)
Presence of a Firewire card does not cause video1394 to be auto-loaded;
only certain types of FireWire cameras cause respective uevents and thus
autoloading of the special-purpose driver video1394.  Ergo, Ionut's
userland has a configuration somewhere which loads video1394 explicitly.

> Btw, swapping default kernel names to devfs names and create symlinks
> for the kernel names is not recommended at all.
> 
> Kay

-- 
Stefan Richter
-=====-==--= ---= =-=--
http://arcgraph.de/sr/
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