The BO handle table exists to avoid double-closing a BO handle,
which aren't reference-counted by the kernel. But if we can
guarantee that there is only ever a single ref for each BO handle,
then we don't need the BO handle table anymore.
This is possible if we create the handle right before the ADDFB2
IOCTL, and close the handle right after. The handles are very
short-lived and we don't need to track their lifetime.
Because of multi-planar FBs, we need to be a bit careful: some
FB planes might share the same handle. But with a small check, it's
easy to avoid double-closing the same handle (which wouldn't be a
big deal anyways).
There's one gotcha though: drmModeSetCursor2 takes a BO handle as
input. Saving the handles until drmModeSetCursor2 time would require
us to track BO handle lifetimes, so we wouldn't be able to get rid
of the BO handle table. As a workaround, use drmModeGetFB to turn the
FB ID back to a BO handle, call drmModeSetCursor2 and then immediately
close the BO handle. The overhead should be minimal since these IOCTLs
are pretty cheap.
Closes: https://github.com/swaywm/wlroots/issues/3164
drmModeAddFB2 doesn't support explicit modifiers. Only accept INVALID
which indicates an implicit modifier and LINEAR which may indicate
that GBM_BO_USE_LINEAR has been used.
Instead of ensuring the renderer and allocator are initialized in each
backend, do it in wlr_backend_autocreate. This allows compositors to
create backends without any renderer/allocator if they side-step
wlr_backend_autocreate.
Since the wlr_backend_get_renderer and backend_get_allocator end up
calling wlr_renderer_autocreate and wlr_allocator_autocreate, it sounds
like a good idea to centralize all of the opimionated bits in one place.
Expose the panel orientation with wlr_drm_connector_get_panel_orientation.
Leave it to the compositor to consume this information and configure the
output accordingly.
Closes: https://github.com/swaywm/wlroots/issues/1581
Modesets require a buffer. The DRM backend tried to auto-enable
outputs when a CRTC becomes available in the past, but now that
fails because no buffer is available.
Instead of having this magic inside the DRM backend, a better
approach is to do it in the compositor or in an optional helper.
Previously, we were copying wlr_output_state on the stack and
patching it up to be guaranteed to have a proper drmModeModeInfo
stored in it (and not a custom mode). Also, we had a bunch of
helpers deriving DRM-specific information from the generic
wlr_output_state.
Copying the wlr_output_state worked fine so far, but with output
layers we'll be getting a wl_list in there. An empty wl_list stores
two pointers to itself, copying it on the stack blindly results in
infinite loops in wl_list_for_each.
To fix this, rework our DRM backend to stop copying wlr_output_state,
instead add a new struct wlr_drm_connector_state which holds both
the wlr_output_state and additional DRM-specific information.
Using GBM to import DRM dumb buffers tends to not work well. By
using GBM we're calling some driver-specific functions in Mesa.
These functions check whether Mesa can work with the buffer.
Sometimes Mesa has requirements which differ from DRM dumb buffers
and the GBM import will fail (e.g. on amdgpu).
Instead, drop GBM and use drmPrimeFDToHandle directly. But there's
a twist: BO handles are not ref'counted by the kernel and need to
be ref'counted in user-space [1]. libdrm usually performs this
bookkeeping and is used under-the-hood by Mesa.
We can't re-use libdrm for this task without using driver-specific
APIs. So let's just re-implement the ref'counting logic in wlroots.
The wlroots implementation is inspired from amdgpu's in libdrm [2].
Closes: https://github.com/swaywm/wlroots/issues/2916
[1]: https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/110
[2]: 1a4c0ec9ae/amdgpu/handle_table.c
The Coordinated Video Timings (CVT) spec [1] defines two types of
timings: the "CVT standard CRT" timings and the "CVT reduced blanking"
timings (see section 3.6).
The standard CRT timings include pauses in the video stream to allow
CRT displays to reposition their electron beam at the end of each
horizontal scan line [2]. While this was desirable a few decades ago,
nowadays we can just generate a CVT reduced blanking timing by default.
wlroots users can still set full custom DRM modes via
wlr_drm_connector_add_mode.
[1]: https://glenwing.github.io/docs/VESA-CVT-1.2.pdf
[2]: https://en.wikipedia.org/wiki/Coordinated_Video_Timings#Reduced_blanking
To retrieve the formats, an allocated crtc is required. If there is no
currently no crtc available, try to allocate it. This reproducable by
having a disabled output and going through a suspend cycle with amdgpu.
On start CRTCs look like this:
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1099] Reallocating CRTCs
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1110] State before reallocation:
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'DP-1' crtc=0 state=1 desired_enabled=1
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'DP-2' crtc=1 state=1 desired_enabled=1
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'HDMI-A-1' crtc=-1 state=0 desired_enabled=0
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'HDMI-A-2' crtc=-1 state=0 desired_enabled=0
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'DVI-D-1' crtc=-1 state=0 desired_enabled=0
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1167] State after reallocation:
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'DP-1' crtc=0 state=1 desired_enabled=1
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'DP-2' crtc=1 state=1 desired_enabled=1
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'HDMI-A-1' crtc=-1 state=0 desired_enabled=0
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'HDMI-A-2' crtc=-1 state=0 desired_enabled=0
00:00:00.588 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'DVI-D-1' crtc=-1 state=0 desired_enabled=0
where DP-1 is than disabled. After suspend/resume, allocation turns into:
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1099] Reallocating CRTCs
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1110] State before reallocation:
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'DP-1' crtc=-1 state=1 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'DP-2' crtc=1 state=3 desired_enabled=1
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'HDMI-A-1' crtc=-1 state=0 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'HDMI-A-2' crtc=-1 state=0 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1116] 'DVI-D-1' crtc=-1 state=0 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1167] State after reallocation:
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'DP-1' crtc=-1 state=1 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'DP-2' crtc=1 state=3 desired_enabled=1
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'HDMI-A-1' crtc=-1 state=0 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'HDMI-A-2' crtc=-1 state=0 desired_enabled=0
00:30:22.680 [DEBUG] [wlr] [backend/drm/drm.c:1174] 'DVI-D-1' crtc=-1 state=0 desired_enabled=0
where the crtc for DP-1 is now NULL. Trying to enable the output results
in:
10:43:36.906 [DEBUG] [sway/config/output.c:351] Turning on output DP-1
10:43:36.906 [DEBUG] [sway/config/output.c:360] Set preferred mode
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [sway/config/output.c:366] Preferred mode rejected, falling back to another mode
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.906 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.906 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.906 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [DEBUG] [sway/config/output.c:400] Auto-detected output scale: 1.000000
10:43:36.907 [DEBUG] [sway/config/output.c:430] Committing output DP-1
10:43:36.907 [DEBUG] [wlr] [backend/drm/drm.c:464] connector DP-1: Can't enable an output without a buffer
10:43:36.907 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
10:43:36.907 [ERROR] [wlr] [types/wlr_output.c:512] Failed to get primary display formats
10:43:36.907 [ERROR] [sway/config/output.c:435] Failed to commit output DP-1
where the primary format can't be queried since there is no crtc
allocated for the connector. Allocating the connector inside
drm_connector_get_primary_formats() fixes this issue. This is possible
since the only user of get_primary_formats() is the swapchain allocation
function, which is only called on output enable. Do the same thing for
the cursor formats in case the user queries them before the output is
enabled.
This allows the kernel to access our buffer damage. Some drivers
can take advantage of this, e.g. for PSR2 panels (Panel Self
Refresh) or for transfer over USB.
Closes: https://github.com/swaywm/wlroots/issues/1267
This reverts commit 85757665e6.
We now check if the output is enabled within wlr_output_send_frame, no
need to handle this explicitly in the DRM backend. This also fixes a
race which was introduced with this commit: if we schedule the flip,
disable and commit the output before the flip happens,
output.frame_pending will not be reset to false. We than always fail to
enable the output subsequently:
00:07:13.276 [INFO] [sway/commands.c:257] Handling command 'output DP-2 enable'
00:07:13.276 [DEBUG] [sway/commands.c:428] Subcommand: enable
00:07:13.276 [DEBUG] [sway/config/output.c:204] Merging on top of existing output config
00:07:13.276 [DEBUG] [sway/config/output.c:227] Config stored for output DP-2 (enabled: 1) (-1x-1@-1.000000Hz position 0,0 scale -1.000000 subpixel unknown transform -1) (bg /home/phoenix/Pictures/Wallpapers/mine/oper.jpg fill) (dpms 1) (max render time: -1)
00:07:13.276 [DEBUG] [sway/config/output.c:351] Turning on output DP-2
00:07:13.276 [DEBUG] [sway/config/output.c:360] Set preferred mode
00:07:13.276 [DEBUG] [wlr] [backend/drm/drm.c:465] connector DP-2: Can't enable an output without a buffer
00:07:13.276 [DEBUG] [wlr] [types/wlr_output.c:689] Attaching empty buffer to output for modeset
00:07:13.277 [DEBUG] [sway/config/output.c:329] Output DPI: 162.560000x161.364706
00:07:13.277 [DEBUG] [sway/config/output.c:400] Auto-detected output scale: 1.000000
00:07:13.277 [DEBUG] [sway/config/output.c:430] Committing output DP-2
00:07:13.277 [DEBUG] [wlr] [types/wlr_output.c:729] Tried to commit a buffer while a frame is pending
since the basic_output_test will always fail.
Reset frame_pending to false even if the output has been disabled in the
meantime.
Fixes https://github.com/swaywm/wlroots/issues/3109
When testing a modeset, make sure the caller has also provided a
buffer. This allows df0e75ba05 ("output: try skipping buffer
allocation if the backend allows it") to work as expected with the
DRM backend.
Closes: https://github.com/swaywm/wlroots/issues/3086
Unless we're dealing with a multi-GPU setup and the backend being
initialized is secondary, we don't need a renderer nor an allocator.
Stop initializing these.
Historically we haven't allowed direct scan-out for legacy KMS,
because legacy misses the functionality to make sure a buffer can
be scanned out. However with renderer v6 the backend can't figure
out anymore whether the buffer comes from its internal swap-chain,
because the backend doesn't have an internal swap-chain.
The legacy KMS API guarantees that the driver won't reject a buffer
as long as it's been allocated with the same parameters as the
previous one. Let's check this in legacy_crtc_test.
This is the cause of the spurious "drmHandleEvent failed" messages
at exit. restore_drm_outputs calls handle_drm_event in a loop without
checking whether the FD is readable, so drmHandleEvent ends up with a
short read (0 bytes) and returns an error.
The loop's goal is to wait for all queued page-flip events to complete,
to allow drmModeSetCrtc calls to succeed without EBUSY. The
drmModeSetCrtc calls are supposed to restore whatever KMS state we were
started with. But it's not clear from my PoV that restoring the KMS
state on exit is desirable.
KMS clients are supposed to save and restore the (full) KMS state on VT
switch, but not on exit. Leaving our KMS state on exit avoids unnecessary
modesets and allows flicker-free transitions between clients. See [1]
for more details, and note that with Pekka we've concluded that a new
flag to reset some KMS props to their default value on compositor
start-up is the best way forward. As a side note, Weston doesn't restore
the CRTC by does disable the cursor plane on exit (see
drm_output_deinit_planes, I still think disabling the cursor plane
shouldn't be necessary on exit).
Additionally, restore_drm_outputs only a subset of the KMS state.
Gamma and other atomic properties aren't accounted for. If the previous
KMS client had some outputs disabled, restore_drm_outputs would restore
a garbage mode.
[1]: https://blog.ffwll.ch/2016/01/vt-switching-with-atomic-modeset.html
wl_event_loop_add_fd was called with a NULL data argument, but the
function expects the data argument to be set to the wlr_drm_backend.
Fixes: 053ebe7c27 ("backend/drm: terminate display on drmHandleEvent failure")
