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

From: Daniel Vetter
Date: Tue Jun 18 2019 - 07:14:26 EST

On Tue, Jun 18, 2019 at 07:56:23AM +0000, Simon Ser wrote:
> 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]:

Yeaht it's a bit a mess, that's why I've suggested we should bite this
bullet and fix it for real. There's a bunch others such bitmasks that many
drivers seem to not set correctly.
Daniel Vetter
Software Engineer, Intel Corporation