On 09/03/2018 06:33 PM, Daniel Vetter wrote: > On Mon, Sep 03, 2018 at 11:16:29AM +0200, Thomas Hellstrom wrote: >> On 08/31/2018 05:30 PM, Thomas Hellstrom wrote: >>> On 08/31/2018 05:27 PM, Emil Velikov wrote: >>>> On 31 August 2018 at 15:38, Michel Dänzer <michel at daenzer.net> 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? >>>>> >>>> AFAICT, the difference is that the standalone vmwgfx uses an internal >>>> copy of drm core. >>>> It doesn't reuse the in-kernel drm, hence it cannot know which minor >>>> it can use. >>>> >>>> -Emil >>> Actually, standalone vmwgfx could perhaps also try to allocate minors >>> from 63 and downwards. That might work, but needs some verification. >>> >> So unfortuntately this doesn't work since the in-tree drm's file operations >> are registered with the DRM_MAJOR. >> So I still think the patch is the way to go. If people are concerned that >> also fbdev file descriptors are allowed, perhaps there are other sysfs >> traits we can look at? > Somewhat out of curiosity, but why do you have to overwrite all of drm? > amdgpu seems to be able to pull their stunt off without ... > -Daniel At the time we launched the standalone vmwgfx, the DRM <-> driver interface was moving considerably more rapidly than the DRM <-> kernel interface. I think that's still the case. Hence less work for us. Also meant we can install the full driver stack with latest features on fairly old VMs without backported DRM functionality. /Thomas
