[Mesa-dev] [PATCH] gbm: add support for loading third-party backend

[Michel Dänzer]

On 25/01/17 07:34 PM, Yu, Qiang wrote:
>> From: Michel Dänzer <michel at daenzer.net>
>> On 24/01/17 12:36 PM, Qiang Yu wrote:
>>> Third-party can put their backend to a directory configured with
>>> '--with-gbm-backenddir' and create a /etc/gbm.conf.d/*.conf file
>>> which contains the backend so file name to overwrite the default
>>> builtin DRI backend.
>>>
>>> The /etc/gbm.conf.d/*.conf will be sorted and the backends added
>>> will be tried one-by-one until one can successfully create a gbm
>>> device. The default DRI backend is tried at last.
>> 
>> If I understand correctly, any third-party backends will always take
>> priority over Mesa-internal backends. Is everyone okay with that? I'm a
>> little worried it might cause problems, but I can't come up with a
>> specific scenario now, and maybe it can be addressed if and when it
>> causes a problem in practice.
> 
> Right, the order can only be overwrite with GBM_BACKEND environment
> variable.
> 
> If we make the DRI backend also configurable by the conf file or give
> a "priority" property to a backend in conf and assign a default
> priority to DRI backend, your worry can be addressed.

Yeah, something like that is probably needed. Otherwise, I suspect e.g.
glamor will break if the amdgpu-pro GBM backend is installed, but the GL
libraries use Mesa, e.g. via GLVND.

Ideally, the GLVND and GBM backend selection mechanisms would be
integrated somehow to prevent that kind of inconsistency (at least by
default, unless the user goes out of their way to shoot themselves in
the foot :).


-- 
Earthling Michel Dänzer               |               http://www.amd.com
Libre software enthusiast             |             Mesa and X developer