Re: The controlD device

[Thomas Hellstrom <thellstrom@vmware.com>]

On 10/21/2011 04:36 PM, Dave Airlie wrote:
> On Fri, Oct 21, 2011 at 3:18 PM, Dave Airlie<airlied@gmail.com>  wrote:
>    
>> On Fri, Oct 21, 2011 at 3:06 PM, Thomas Hellstrom<thellstrom@vmware.com>  wrote:
>>      
>>> Dave,
>>>
>>> What is the drm control device nodes really used for?
>>>
>>> On my fc14 system it seems like it has world rw privileges, and full access
>>> to all modesetting ioctls.
>>> Is that the intention?
>>>        
>> No, and I just realised we packaged a broken udev rule.
>>
>> It should be root only, oops.
>>
>> Its intention is for setting up multi-seat and gpgpu access to the drm.
>>
>> change /etc/udev/rules.d/91-modeset.rules to be 0600.
>>      
> I've filed updates to Fedora to fix this, no other distro should be
> using or caring about these device nodes yet, since we never really
> got GPGPU going yet.
>
> Dave.
>    
Sounds good. I was actually mostly curios on the intended usage pattern 
of the control node.
I found some things on the DRM wikis, but it doesn't at all seem 
consistent with what's in DRM.

Why do we have CONTROL_ALLOW on all modesetting ioctls?, also this code 
in drm_crtc.c  seems odd:

if (file_priv->master->minor->type == DRM_MINOR_CONTROL) {
...

Isn't that equivalent to

if (file_priv->minor->type == DRM_MINOR_CONTROL) { ?

Any enlightenment would be appreciated.

Thanks,
/Thomas