On Tue, 03 Apr 2018 10:57:56 +0200, Christian K6nig wrote: > > Am 03.04.2018 um 10:36 schrieb 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. > > Correct, but I agree that even in this situation it would be very > helpful to prevent the gfx drivers from loading and fallback to > efifb/vesafd (or whatever the platform provides). > > It's just that the "nomodeset" and "amdgpu.modeset=0" options are > really not well named for this task. Agreed with the naming mess. But OTOH, it's already a thing that is too popular to kill. You can add a more suitable option name, but you cannot drop these existing ones easily. It's already in a gray zone of the golden "don't break user-space" rule. thanks, Takashi
