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Date:   Tue, 18 Jun 2019 07:56:23 +0000
To:     Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
From:   Simon Ser <contact@emersion.fr>
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Subject: Re: [PATCH V2 4/5] drm/vkms: Use index instead of 0 in possible crtc
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Interestingly, even with the previous code, possible_crtcs=3D1 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=3D0, 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