drm: GPF in drm_getcap

[Dmitry Vyukov]

On Mon, Nov 28, 2016 at 8:14 AM, Michel Dänzer <michel at daenzer.net> wrote:
> On 28/11/16 03:55 PM, Daniel Vetter wrote:
>> On Sat, Nov 26, 2016 at 7:22 PM, David Herrmann <dh.herrmann at gmail.com> wrote:
>>> On Sat, Nov 26, 2016 at 7:07 PM, Dmitry Vyukov <dvyukov at google.com> wrote:
>>>> grep "card0" dmesg:
>>>> [    5.298617] device: 'card0': device_add
>>>> [    5.298946] PM: Adding info for No Bus:card0
>>>> [    6.436178] device: 'card0': device_add
>>>> [    6.436488] PM: Adding info for No Bus:card0
>>>>
>>>>
>>>> # ls -l /dev/dri/card0
>>>> crw-rw---T 1 root video 226, 0 Nov 26 18:05 /dev/dri/card0
>>>>
>>>> # ls -lt /sys/class/drm/card0/device/
>>>> ls: cannot access /sys/class/drm/card0/device/: No such file or directory
>>>>
>>>> # ls -lt /sys/class/drm/card0/device/driver
>>>> ls: cannot access /sys/class/drm/card0/device/driver: No such file or directory
>>>
>>> Looks like vgem. Something like this should help:
>>>
>>>     https://gist.github.com/dvdhrm/1bcdf4f3485aa1614a0198a7b90515e2
>>>
>>> I wonder whether it would be more appropriate to return -ENOTSUPP rather than 0.
>
> Can't see how that would matter FWIW.
>
>
>> Seems a bit overkill, but can't hurt. This is most likely a
>> regression, probably introduced in
>>
>> commit f837297ad82480024d3ad08cd84f6670bcafa862
>> Author: Michel Dänzer <michel.daenzer at amd.com>
>> Date:   Mon Aug 8 16:23:39 2016 +0900
>>
>>     drm: Add DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE/RELATIVE flags v2
>>
>> Michel, can you pls take care of this? Either with a minimal fix, or
>> by adopting David's patch?
>
> Can't we just use David's patch as-is? If not, I think Dmitry or someone
> else would be better equipped than me to extract a minimal fix from it
> and test it.


I know nothing about DRM code. Reproducer is attached to the first email.