[PATCH libdrm] libdrm: Allow dynamic drm majors on linux

[Thomas Hellstrom]

On 08/31/2018 04:49 PM, Michel Dänzer wrote:
> On 2018-08-31 4:46 p.m., Thomas Hellstrom wrote:
>> On 08/31/2018 04:38 PM, Michel Dänzer wrote:
>>> [ Adding the amd-gfx list ]
>>>
>>> On 2018-08-31 3:05 p.m., Thomas Hellstrom wrote:
>>>> On 08/31/2018 02:30 PM, Emil Velikov wrote:
>>>>> On 31 August 2018 at 12:54, Thomas Hellstrom <thellstrom at vmware.com>
>>>>> wrote:
>>>>>> To determine whether a device node is a drm device node or not, the
>>>>>> code
>>>>>> currently compares the node's major number to the static drm major
>>>>>> device
>>>>>> number.
>>>>>>
>>>>>> This breaks the standalone vmwgfx driver on XWayland dri clients,
>>>>>>
>>>>> Any particular reason why the code doesn't use a fixed node there?
>>>>> It will make the diff vs the in-kernel driver a bit smaller.
>>>> Because then it won't be able to interoperate with other in-tree
>>>> drivers, like virtual drm drivers or passthrough usb drm drivers.
>>>> There is no clean way to share the minor number allocation with in-tree
>>>> drm, so standalone vmwgfx is using dynamic major allocation.
>>> I wonder why I haven't heard of any of these issues with the standalone
>>> version of amdgpu shipped in packaged AMD releases. Does that also use a
>>> different major number? If yes, maybe it's just that nobody has tried
>>> Xwayland clients with that driver. If no, how does it avoid the other
>>> issues described above?
>>>
>>>
>> Is standalone AMD supposed to be able to coexist with in-tree drm drivers?
> Yes, it does, it's working e.g. on laptops with an Intel integrated and
> an AMD discrete GPU.
>
>

Hmm. The symptoms with xf86-video-vmware are that when mesa initializes, 
we get:
MESA-LOADER: failed to retrieve device information
MESA-LOADER: failed to retrieve device information
MESA-LOADER: failed to retrieve device information

but then vmwgfx_dri.so loads anyway.

With XWayland, mesa just silently tries swrast instead of vmwgfx.

Not sure this has always been the case though. It might be due to a 
recent XWayland change. In any case, the change to libdrm silence the 
warnings on Xorg and makes mesa try vmwgfx on XWayland.

/Thomas