Udev problem

[Mikkel L. Ellertson]

Mikkel L. Ellertson wrote:
> Anne Wilson wrote:
>> I use a video capture card for my analogue camcorder, and a webcam.  Udev's 
>> habit of randomly setting video0 and video1 are a problem, so after a good 
>> bit of reading I set out to create persistent symlinks.  The idea is that the 
>> device is recognised and the link is made to whichever video* is appropriate.  
>> The links are created, but there are problems.
>>
>> First, /dev/DC10plus does not get removed at shutdown.  I'm not sure 
>> about /dev/webcam, I haven't seen any error messages (though I haven't 
>> thoroughly examined the logs).  Looking at the permissions on the links,they 
>> are owned root:root.  
>>
>> lrwxrwxrwx 1 root root 14 Jan 18 16:39 /dev/DC10plus -> mapper/control
>> lrwxrwxrwx 1 root root 6 Jan 18 16:39 /dev/webcam -> video0
>>
>> If I chown to anne:root they are properly deleted on shutdown.
>>
>> Attempting to use /dev/DC10plus gives me these errors:
>>
>> **ERROR: [lavrec] Error opening video-device (/dev/DC10plus): Permission 
>> denied
>> **ERROR: [lavrec] Something went wrong while setting up the card
>>
>> After chown:
>>
>> **ERROR: [lavrec] Error setting channel: Permission denied
>> **ERROR: [lavrec] Something went wrong while setting up the card
>>
>> It all seems to revolve around permissions.  Also, it looks as though anne may 
>> need to own the link in order to use it.  If so, I have to find some way of 
>> that being automatically set.
>>
>> Any thoughts?
>>
>> Anne
>>
> When you are using symlinks, the permissions that matter are the
> permissions of the file the link points to. You can not set the
> permissions of the symlink. You can set the permissions of the
> device in the udev rules. But you have to be careful because some
> devices get the permission changed by console.perms, so the udev
> permissions do not have any affect. Changing the permissions as root
> will only last until the owner of the console changes. Then
> console.perms will reset them.
> 
An added note - the vedio device permissions are controlled by
console.perms by default.

<v4l>=/dev/video* /dev/radio* /dev/winradio* /dev/vtx* /dev/vbi* \
      /dev/video/*

So you may need to tweak the v4l rule, or remove some devices from
the line shown above.

Mikkel
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