[PATCH 2/2] drm/amdgpu: Add modeset module option

[Michel Dänzer]

On 2018-04-01 07:45 PM, Ilia Mirkin wrote:
> On Sun, Apr 1, 2018 at 1:39 PM, Christian König
> <christian.koenig at amd.com> wrote:
>> Am 30.03.2018 um 22:45 schrieb Takashi Iwai:
>>>
>>> amdgpu driver lacks of modeset module option other drm drivers provide
>>> for enforcing or disabling the driver load.  Interestingly, the
>>> amdgpu_mode variable declaration is already found in the header file,
>>> but the actual implementation seems to have been forgotten.
>>>
>>> This patch adds the missing piece.
>>
>>
>> NAK, modesetting is mandatory for amdgpu and we should probably remove the
>> option to disable it from other DRM drivers without UMS support as well
>> (pretty much all of them now).
>>
>> If you want to prevent a driver from loading I think the correct way to do
>> so is to give modprobe.blacklist=amdgpu on the kernel commandline.
>>
>> That would remove the possibility to prevent the driver from loading when it
>> is compiled in, but I don't see much of a problem with that.
> 
> Having a way to kill the graphics driver is a very useful debugging
> tool, and also a quick and easy way to get out of an unpleasant
> situation where graphics are messed up / system hangs / etc. The
> modprobe blacklist kernel arg only works in certain environments (and
> only if it's a module).

Building amdgpu into the kernel isn't feasible for a generic kernel such
as a distro one, because it would require including all microcode into
the kernel as well (12M right now, and growing).

If a user decides to build amdgpu into their custom kernel and runs into
trouble due to that, that's "doctor, it hurts if I do this" territory.


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