backend/drm: use DRM_IOCTL_MODE_CLOSEFB instead of RMFB

RMFB implicitly performs a modeset to turn off any CRTC which is using the FB. This prevents seamless transitions between two DRM masters from working.

Use the new CLOSEFB IOCTL which doesn't turn off anything and leave it up to the compositor to turn off outputs on shutdown if it wants to.

FWIW, this was tested by adding a sleep(5) after closing our DRM FD but before exiting. Without this patch, I see a black screen due to RMFB. With this patch, the last frame is still displayed.

mentioned in merge request !4402 (merged)

References: https://lore.kernel.org/all/20231020101926.145327-2-contact@emersion.fr/

mentioned in commit emersion/wlroots@e24c4ec7

Kernel patch has been merged to drm-misc-next.

libdrm patch: mesa/drm!332 (merged)

mentioned in commit nouvelles/kernel@d208d875

mentioned in commit emersion/wlroots@b0bd8628

added 49 commits

• 983491c2...c6b49852 - 48 commits from branch wlroots:master
• 6f18be24 - backend/drm: use DRM_IOCTL_MODE_CLOSEFB instead of RMFB

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marked this merge request as ready

Updated to use the libdrm wrapper, and fallback to RMFB if the kernel is too old.

added waiting on upstream label

removed waiting on upstream label

added 47 commits

• 6f18be24...395a08f5 - 46 commits from branch wlroots:master
• ae3d7a69 - backend/drm: use DRM_IOCTL_MODE_CLOSEFB instead of RMFB

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enabled an automatic merge when the pipeline for ae3d7a69 succeeds

merged

mentioned in issue #3807 (closed)