Re: [PATCH V2 4/5] drm/vkms: Use index instead of 0 in possible crtc

[Simon Ser]

Interestingly, even with the previous code, possible_crtcs=1 was
exposed to userspace [1]. I think this is because of a safeguard in
drm_crtc_init_with_planes (drm_crtc.c:284) which sets the primary and
cursor plane's possible_crtcs to the first CRTC if zero.

If we want to warn on possible_crtcs=0, we should probably remove this
safeguard. Checking first whether this safeguard is used by any driver
is probably a good idea.

[1]: https://drmdb.emersion.fr/devices/f218d1242714