On 2018-04-03 11:02 AM, Takashi Iwai wrote: > 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. That's quite a stretch argument, given that amdgpu has never supported the modeset parameter. Also, module parameters aren't UAPI. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Mesa and X developer
