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? /Thomas > /Thomas >
