PRIME support for buffer sharing has become mandatory since the renderer
rewrite. Make sure we check for the appropriate capabilities in backend,
allocator and renderer.
See also #2819.
Downgrade errors to DEBUG level, because drm_fb_create is used in
test_buffer, so errors aren't always fatal. Add ERROR logs at call
sites where a failure is fatal, to make it clear something wrong
happened.
If the import to KMS succeeds, we have a better chance to be able to
scan it out.
Importing is also necessary for test-only commits, which we want to
add in the future.
Compute only the transform matrix in the output. The projection matrix
will be calculated inside the gles2 renderer when we start rendering.
The goal is to help the pixman rendering process.
In 93cd3a79b2 ("backend/drm: stop using GBM flags"), we stopped
using the GBM_BO_USE_LINEAR flag in favor of a modifier list set
to { DRM_FORMAT_MOD_LINEAR }. However, the last argument of
drm_plane_init_surface disables modifiers -- so the buffer will just
get allocated with an implicit modifier, without necessarily being
LINEAR.
To fix this, allow modifiers when allocating the cursor buffers.
wlr_drm_plane.formats should already have the necessary LINEAR
restrictions.
Fixes: 93cd3a79b2 ("backend/drm: stop using GBM flags")
This allows a compositor to get a KMS connector object ID from a
wlr_output. The compositor can then query more information about
the connector via libdrm.
This gives more freedom to compositors and allows them to read
KMS properties that wlroots doesn't know about. For instance,
they could read the EDID or the suggested_{X,Y} properties and
change their output configuration based on that.
The subconnector property indicates the connector sub-type. This is
useful because that usually indicates what kind of connector the user
has plugged in to their monitor, e.g. a DisplayPort-to-DVI cable will
indicate a DVI subconnector. Also some laptops have non-DP connectors
that are internally linked to a DP port on the GPU.
Set the output description accordingly.
See https://drmdb.emersion.fr/properties/3233857728/subconnector
Since 5b1b43c68c ("backend/drm: make wlr_drm_plane.{pending,queued,current}_fb
pointers"), current_fb can be NULL if there's no buffer. If current_fb
is not NULL, current_fb->wlr_buf is guaranteed to not be NULL.
Closes: https://github.com/swaywm/wlroots/issues/2634
Stop keeping track of buffers on the parent GPU when multi-GPU is used.
This removes support for export_dmabuf on secondary GPUs, but renderer
v6 will bring this back by managing the swapchains in wlr_output instead
of the backends.
wlr_drm_connector.crtc may be updated by the DRM backend while a
page-flip is pending. In this case, the page-flip handler won't be able
to find the right wlr_drm_connector from the CRTC ID.
Save the CRTC when performing a page-flip to ensure we always find the
right connector when we get the event.
We now properly mark the cursor plane's formats as linear-only, and we
now have a version of wlr_drm_format_intersect that handles the case of
linear-only formats and implicit modifiers.
We can remove the special drm_plane_init_surface flag we had for cursor
planes. This also allows us to use a non-linear layout for cursor planes
on drivers that support it.
Tested on amdgpu GFX9.
If the kernel driver doesn't support modifiers, it still expects cursor
FBs to have a LINEAR layout. See [1] for expectations for framebuffers
attached to the cursor plane.
[1]: https://patchwork.freedesktop.org/patch/408512/
Parse WLR_DRM_NO_MODIFIERS at startup. Don't parse IN_FORMATS when
WLR_DRM_NO_MODIFIERS is set, so that the legacy behaviour is better
reproduced.
When modifiers aren't supported, try the initial page-flip once only.
This was lost during the refactoring. We were previously calling
wlr_output_destroy, which destroyed the connector as well.
Fixes: 248c7787c7 ("backend/drm: refactor wlr_output destruction")
The DRM backend is a little special when it comes to wlr_outputs: the
wlr_drm_connectors are long-lived and are created even when no screen is
connected.
A wlr_drm_connector only advertises a wlr_output to the compositor when
a screen is connected. As such, most of wlr_output's state is invalid
when the connector is disconnected.
We want to stop using wlr_output state on disconnected connectors.
Introduce wlr_drm_connector.name which is always valid regardless of the
connector status to avoid reading wlr_output.name when disconnected.
Simplify and unify connector-specific logging with a new
wlr_drm_conn_log macro. This makes it easier to understand which
connector a failure is about, without having to explicitly integrate the
connector name in each log message.
The workaround is broken because drm_fb_acquire doesn't leave the EGL
context current anymore. We'll need to re-introduce it.
References: https://github.com/swaywm/wlroots/issues/2525
gbm_bo_create_with_modifiers doesn't take GBM flags, so our
wlr_gbm_allocator interface doesn't either. We were still internally
using GBM flags in the DRM backend, leading to awkward back-and-forth
conversions.
The only flag passed to drm_plane_init_surface was GBM_BO_USE_LINEAR, so
turn that into a bool to make sure other flags can't be passed in.
Move the "force linear" logic out of init_drm_surface, because the
supplied wlr_drm_format should already contain that information.
After discussing with Pekka and Daniel on #dri-devel, we concluded [1]
that user-space shouldn't need to force-probe connectors. Force-probing
can take some time, so using drmModeGetConnectorCurrent can result in
faster start-up.
Users can manually trigger a force-probe if necessary:
echo detect | sudo tee /sys/class/drm/card0-DP-1/status
Or just by running a tool like drm_info.
A similar change has been submitted to Weston [2].
[1]: https://lists.freedesktop.org/archives/dri-devel/2020-November/287728.html
[2]: https://gitlab.freedesktop.org/wayland/weston/-/issues/437
We would always return the GAMMA_LUT_SIZE property if available, and
only fall back to legacy gamma size otherwise. This leads to issues if
both are available in differs in size while we use the legacy backend.
Ensure that we only return the legacy size if we're using the legacy
backend.
Closes: https://github.com/swaywm/wlroots/issues/2429
When performing a modeset, the DRM backend will request a page-flip
event. However frame_pending wasn't set to true, so any subsequent
wlr_output_schedule_frame calls would imemdiately trigger a synthetic
frame event, asking the compositor to submit a new frame. Committing the
new frame fails with "a page-flip is already pending" error in the DRM
backend.
When an output is disabled one last pageflip will happen to disable it.
Currently this pageflip causes a frame event.
Since the output is disabled we don't want to send this frame event.
get_drm_prop_blob does not set path_len if it returns NULL. Check the
return value before path_len to avoid reading uninitialized memory.
(Granted, this doesn't change the logic at all, but it does make
Valgrind a bit happier.)
drm_connector_set_cursor wasn't checking the return value of the
drm_surface_make_current call. On failure, this results in a failed
assertion in wlr_renderer_begin (because no rendering context is
current).
The output backend API is now mostly state-less thanks to the atomic
hooks (commit and test). There is one exception though: attach_render.
This function makes the rendering context current. However sometimes the
compositor might decide not to render after attach_render (e.g. when
there's nothing new to render to the back buffer). Thus
wlr_output_rollback has been introduced to revert the pending state.
Because the output backend API is mostly state-less, the only thing
wlr_output_impl.rollback needs to do is revert the current rendering
context. Rename the function to rollback_render to make this clear. Add
a check in the common wlr_output code to only call rollback_render when
attach_buffer has been previously called.
On the long term, we'll be able to remove attach_render and
rollback_render together.
This patch fixes this failure:
01:57:16.642 [ERROR] [backend/drm/drm.c:360] Failed to page-flip output 'eDP-1': a page-flip is already pending
01:57:16.684 [ERROR] [backend/drm/drm.c:360] Failed to page-flip output 'eDP-1': a page-flip is already pending
01:57:16.684 [ERROR] [backend/drm/drm.c:732] Failed to initialize renderer on connector 'eDP-1': initial page-flip failed
01:57:16.684 [ERROR] [backend/drm/drm.c:805] Failed to initialize renderer for plane
01:57:16.684 [sway/config/output.c:423] Failed to commit output eDP-1
References: https://github.com/swaywm/sway/issues/5101
When the mode, status or buffer hasn't changed, drm_connector_commit was
a no-op. Because of this individual changes to the gamma LUT or adaptive
sync status were ignored (if committed without a buffer).
Instead, perform a commit to apply the changes.
A test commit doesn't apply the pending state.
The CRTC state will be populated again if the compositor decides to
perform a regular commit afterwards.
Previously, we only had the pending state (crtc->pending, crtc->mode and
crtc->active). This causes issues when a commit fails: the pending state
is left as-is, and the next commit may read stale data from it.
This will also cause issues when implementing test-only commits: we need
to rollback the pending CRTC state after a test-only commit.
Introduce separate pending and current CRTC states. Properly update the
current state after a commit.
retry_pageflip is now dead code, since drm_connector_start_renderer
isn't called anymore. It was previously called when enabling an output.
The name "retry_pageflip" was a little confusing because the function
retried a modeset and the timer wasn't set up while performing a simple
page-flip.
Let's just remove this altogether for now. We can discuss whether it's
worth it to bring it back. Should we only do it on failed page-flips?
Should we only do it on EBUSY?
After swapping buffers, it doesn't make sense to perform more rendering
operations. Unset the context to reflect this.
This commit makes it so the context is always only current between
wlr_egl_make_current and wlr_egl_swap_buffers.
This is an alternative to [1].
[1]: https://github.com/swaywm/wlroots/pull/2212
This function can be called after wlr_egl_make_current to cleanup the
EGL context. This avoids having lingering EGL contexts that make things
work by chance.
Closes: https://github.com/swaywm/wlroots/issues/2197
dealloc_crtc was destroying GBM surfaces, but the cursor_enabled flag
was left as-is. When re-enabling the output, atomic_crtc_pageflip would
try enabling the cursor plane, but would fail because no framebuffer is
available.
Closes: https://github.com/swaywm/wlroots/issues/2150
When an output is enabled and modeset at the same time,
drm_connector_commit would first try to modeset then try to commit. This
won't work because both will trigger a page-flip. KMS will reject that.
Change the logic to only enable an output if no modeset has been
requested. The logic in wlr_output already checks that the user isn't
doing a modeset and disabling the output at the same time.
We have a workaround for legacy drivers that support drmModeSetCursor
without exposing a cursor plane. It doesn't work anymore now that we've
moved to a more atomic interface.
Let's just remove this workaround and fallback to software cursors.
Closes: https://github.com/swaywm/wlroots/issues/2166
We don't need a per-CRTC atomic request anymore. Let's make the request
per-commit so that it's easier to debug.
This is also groundwork for supporting wlr_output_test properly.
GAMMA_LUT_SIZE isn't an atomic property. It can be used with the legacy
interface too. So we can unify both codepaths and remove
wlr_drm_interface.crtc_get_gamma_size.
It's no guaranteed to exist though, so we still need to keep the
fallback.
The logs don't currently display the importance of a line. It's easy to
read "skipping page-flip" as a debug message instead of an error
message.
Change the error message to make it more explicit.
References: https://github.com/swaywm/wlroots/pull/2147
Reconnecting an external display fails on initial
page-flip. This occurs when the pageflip_pending flag
has been set on the connector at the time the monitor
is removed. Once the connector's CRTC has been deallocated,
page_flip_handler cannot find the connector by its crtc_id,
so pageflip_pending will remain set. This causes
initialization to fail when the monitor is reconnected
with the error messages:
Skipping pageflip on output 'X'
Failed to initialize renderer on connector 'X': initial page-flip failed
To fix this problem, clear the pageflip_pending flag
when cleaning up the connector.
This is a type which manages gbm_surfaces and imported dmabufs in the
same place, and makes the lifetime management between the two shared. It
should lead to easier to understand code, and fewer special cases.
This also contains a fair bit of refactoring to start using this new
type.
Co-authored-by: Simon Ser <contact@emersion.fr>
Most of the pending output state is not forwarded to the backend prior
to an output commit. For instance, wlr_output_set_mode just stashes the
mode without calling any wlr_output_impl function.
wlr_output_impl.commit is responsible for applying the pending mode.
However, there are exceptions to this rule. The first one is
wlr_output_attach_render. It won't go away before renderer v6 is
complete, because it needs to set the current EGL surface.
The second one is wlr_output_attach_buffer.
wlr_output_impl.attach_buffer is removed in [1].
When wlr_output_rollback is called, all pending state is supposed to be
cleared. This works for all the state except the two exceptions
mentionned above. To fix this, introduce wlr_output_impl.rollback.
Right now, the backend resets the current EGL surface. This prevents GL
commands from affecting the output after wlr_output_rollback.
This patch is required for FBO-based outputs to work properly. The
compositor might be using FBOs for its own purposes [2], having leftover
FBO state can have bad consequences.
[1]: https://github.com/swaywm/wlroots/pull/2097
[2]: https://github.com/swaywm/wlroots/pull/2063#issuecomment-597614312
Check that buffer can be scanned out in wlr_output_test instead of
wlr_output_attach_buffer. This allows the backend to have access to the
whole pending state when performing the check.
This brings the wlr_output API more in line with the KMS API.
This removes the need for wlr_output_attach_buffer to return a value,
and for wlr_output_impl.attach_buffer.
Consumers call wlr_buffer_lock. Once all consumers are done with the
buffer, only the producer should have a reference to the buffer. In this
case, we can release the buffer (and let the producer re-use it).
This function allowed backends to provide a custom function for frame
scheduling. Before resuming the rendering loop, the DRM and Wayland
backends would wait for vsync.
There isn't a clear benefit of doing this. The only upside is that we
get more stable timings: the delay between two repaints doesn't change too
much and is close to a mutliple of the refresh rate.
However this introduces latency, especially when a client misses a
frame. For instance a fullscreen game missing vblank will need to wait
more than a whole frame before being able to display new content. This
worst case scenario happens as follows:
- Client is still rendering its frame and cannot submit it in time
- Deadline is reached
- Compositor decides to stop the rendering loop since nothing changed on
screen
- Client finally manages to render its frame, submits it
- Compositor calls wlr_output_schedule_frame
- DRM backend waits for next vblank
- The wlr_output frame event is fired, compositor draws new content on screen
- On the second next vblank, the new content reaches the screen
With this patch, the wlr_output frame event is fired immediately when
the client submits its late frame.
This change also makes it easier to support variable refresh rate, since
VRR is all about being able to present too-late frames earlier.
References: https://github.com/swaywm/wlroots/issues/1925
The previous PR was overzealous in adding a finish_drm_surface call
which was also done by the caller. Remove the call and also move the
comment to the correct code location.
In some cases modesets fail if the planes are initialized with
modifiers. Since in this case possibly all planes need to reinitialized,
which is not possible in the current wlroots design, add an environment
variable for affected users.
This fixes a segfault in drm_connector_set_mode (mode = NULL).
This happens because we set wlr_output.enabled to true if the connector
is attached to the CRTC. When the user disables an output in the
wlroots-based compositor, switches to another VT (enabling the output),
then switches back, wlroots sets wlr_output.enabled to true but
wlr_output.current_mode is NULL.
We should consider not reading properties from KMS after a TTY switch,
disabling all connectors. However this may result in flickering (outputs
being disabled then re-enabled).
Closes: https://github.com/swaywm/wlroots/issues/1874
wlr_output.description is a string containing a human-readable string
identifying the output. Compositors can customise it via
wlr_output_set_description, for instance to make the name more
user-friendly.
References: https://github.com/swaywm/wlroots/issues/1623
This is set to the value of wlr_output.commit_seq when the frame has
been submitted. This allows tracking presentation with more then 1 full
frame of latency.
References: https://github.com/swaywm/wlroots/issues/1917
Instead of checking that the path property is not 0 to determine if the
connector is an MST connector, check if the path contains the mst:
string.
Fixes#1813
Instead of waiting for the next pageflip, destroy the output immediately
since we can now handle flips for outputs which no longer exist.
Also demote the missing crtc on flip to debug.
Fixes#1739
This commit makes more output properties (mode, enabled, scale and transform)
atomic. This means that they are double-buffered and only applied on commit.
Compositors now need to call wlr_output_commit after setting any of those
properties.
Internally, backends still apply properties sequentially. The behaviour should
be exactly the same as before. Future commits will update some backends to take
advantage of the atomic interface. Some backends are non-atomic by design, e.g.
the X11 backend or the legacy DRM backend.
Updates: https://github.com/swaywm/wlroots/issues/1640
The documentation for wayland-server.h says:
> Use of this header file is discouraged. Prefer including
> wayland-server-core.h instead, which does not include the server protocol
> header and as such only defines the library PI, excluding the deprecated API
> below.
Replacing wayland-server.h with wayland-server-core.h allows us to drop the
WL_HIDE_DEPRECATED declaration.
atomic and legacy now both pass the backend as the user data for the
pageflip event. We than retrieve the correct connector by matching on
the crtc_id passed to the page_flip_handler2.
Wlroots also requires the DRM_CRTC_IN_VBLANK_EVENT capability now.
Fixes#1297
The backend doesn't need to handle transform changes, since everything is done
in software. In fact, all of the implementations were all identical and just
set the transform.
We could add support for hardware transforms, but:
- This would require a different field (something like hardware_transform)
- Not all combinations are possible because there often are hardware
limitations
- The Wayland protocol isn't ready for this (in particular xdg-output, see [1])
This belongs to a different patch series anyway.
[1]: https://patchwork.freedesktop.org/series/52324/
This updates the backend part of the output API. This is mostly renaming:
make_current becomes attach_render and swap_buffers becomes commit.
This also fixes the RDP backend to support NULL damage.
The deleted includes are redundant, because other headers will include
the necessary files. Additionally, they cause build failures, because
including EGL/egl.h or EGL/eglext.h directly, instead of through
wlr/render/egl.h or wlr/render/interface.h, will mean that
MESA_EGL_NO_X11_HEADERS will not have been defined, and so the EGL
headers will attempt to pull in unnecessary X11 headers that may not
exist on the system.
For the headers produced by glgen.sh, the includes couldn't simply be
deleted, because no other header would include the EGL headers. Neither
wlr/render/egl.h or wlr/render/interface.h felt appropriate to include,
so I opted instead to copy the MESA_EGL_NO_X11_HEADERS definition before
the EGL includes.
* wlr_output: Indicate modes link
* wlr_output: Introduce preferred flag
This indicates an outputs preferred mode.
* drm: Set preferred flag for an outputs preferred mode
If *changed_outputs is not supplied by the calling function, track the local
allocation with a bool variable and free the allocation at the end of the
function.
On DRM resume, such as switching back to a TTY, the output needs to be
modeset to the current mode. However, wlr_output_set_mode will return
early when attempting to set the mode to the current mode. This just
steps around wlr_output_set_mode and calls drm_connector_set_mode
directly.
There is no point in modesetting an output to a mode that it is already
set to. Modesetting will cause the output to briefly flicker which is
undesirable for a noop. This returns early in `drm_connector_set_mode`
when attempting to modeset to the current mode.
In order for a surface to be used as a cursor plane framebuffer, it
appears that requiring the buffer to be linear is sufficient.
GBM_BO_USE_SCANOUT is added in case GBM_BO_USE_LINEAR isn't sufficient
on untested hardware.
Fixes#1323
Removed wlr_drm_plane.cursor_bo as it does not serve any purpose
anymore.
Relevant analysis (taken from the PR description):
While trying to implement a fix for #1323, I found that when exporting
the rendered surface into a DMA-BUF and reimporting it with
`GBM_BO_USE_CURSOR`, the resulting object does not appear to be valid.
After some digging (turning on drm-kms debugging and switching to legacy
mode), I managed to extract the following error: ```
[drm:__setplane_check.isra.1 [drm]] Invalid pixel format AR24
little-endian (0x34325241), modifier 0x100000000000001 ``` The format
itself refers to ARGB8888 which is the same format as
`renderer->gbm_format` used in master to create the cursor bo. However,
using `gbm_bo_create` with `GBM_BO_USE_CURSOR` results in a modifier of
0. A modifier of zero represents a linear buffer while the modifier of
the surface that is rendered to is `I915_FORMAT_MOD_X_TILED` (see
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/include/uapi/drm/drm_fourcc.h?h=v4.20.6#n263).
In order to fix this mismatch in modifier, I added the
`GBM_BO_USE_LINEAR` to the render surface and everything started to work
just fine. I wondered however, whether the export and import is really
necessary. I then decided to test if the back buffer of the render
surface works as well, and at least on my hardware (Intel HD 530 and
Intel UHD 620) it does. This is the patch in this PR and this requires
no exporting and importing.
I have to note that I cheated in order to import DMA_BUFs into a cursor
bo when doing the first tests, since on import the Intel drivers check
that the cursor is 64x64. This is strange since cursor sizes other than
64x64 have been around for quite some time now
(https://lists.freedesktop.org/archives/mesa-commit/2014-June/050268.html).
Removing this check made everything work fine. I later (while writing
this PR) found out that `__DRI_IMAGE_USE_CURSOR` (to which
`GBM_BO_USE_CURSOR` translates) has been deprecated in mesa
(https://gitlab.freedesktop.org/mesa/mesa/blob/master/include/GL/internal/dri_interface.h#L1296),
which makes me wonder what the usecase of `GBM_BO_USE_CURSOR` is. The
reason we never encountered this is that when specifying
`GBM_BO_USE_WRITE`, a dumb buffer is created trough DRM and the usage
flag never reaches the Intel driver directly. The relevant code is in
https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/gbm/backends/dri/gbm_dri.c#L1011-1089
. From this it seems that as long as the size, format and modifiers are
right, any surface can be used as a cursor.
We create the EGL config with GBM_FORMAT_ARGB8888, but then initialize GBM BOs
with GBM_FORMAT_XRGB8888. This mismatch confuses Mesa.
Instead, we can always use GBM_FORMAT_ARGB8888, and use DRM_FORMAT_XRGB8888
when calling drmModeAddFB2.
Fixes https://github.com/swaywm/wlroots/issues/1438
When there aren't enough CRTCs for all outputs, we try to move a CRTC from a
disabled output to an enabled one. When this happens, the old output's state
wasn't changed, so the compositor thought it was still enabled and rendering.
This commit marks the old output as WLR_DRM_CONN_NEEDS_MODESET and sets its
current mode to NULL.
This commit changes `scan_drm_connectors` to add new outputs to the end of the
list. That way, it's easier to understand what's going on with indices.
When we need to destroy outputs, we now walk the list in reverse order. This
ensures indices remain correct while iterating and removing items from the
list.
We now also make outputs without a CRTC disappear (those are in
WLR_DRM_CONN_NEEDS_MODESET state).
There was a missing copy_drm_surface_mgpu call in drm_connector_schedule_frame
so we asked for a pageflip with an unknown BO, resulting in ENOENT.
Additionally, this commit makes schedule_frame return a bool indicating
failures. This allows schedule_frame_handle_idle_timer to only set
frame_pending to true if a frame has been successfully scheduled. Thus, if a
pageflip fails, rendering won't be blocked forever anymore.
In case a pageflip is already pending, true is returned because a frame has
already been scheduled and will be sent sometime soon.
If a pageflip is pending before cleanup, it's still pending after. This
is used line 1177: drm_connector_cleanup is called and
conn->pageflip_pending is checked afterwards.
Fixes#1297
This prevents the idle event to be activated on a destroyed
output.
This also makes the backend responsible for free-ing modes, as it
is the one allocating them and adding them to the list. Note that
the DRM backend (the only one using modes) already frees them.
This desynchronizes our rendering loop with the vblank cycle.
In case a compositor doesn't swap buffers but schedules a frame,
emitting a frame event immediately enters a busy-loop.
Instead, ask the backend to send a frame when appropriate. On
Wayland we can just register a frame callback on our surface. On
DRM we can do a no-op pageflip.
Fixes#617Fixesswaywm/sway#2748
When a pageflip is pending, we'll get a DRM event for the connector
in the future. We don't want to free the connector immediately
otherwise we'll use-after-free in the pageflip handler.
This commit adds a new state, "DISAPPEARED". This asks the pageflip
handler to destroy the output after it's done pageflipping.
This commit allows outputs that need a CRTC to steal it from
user-disabled outputs. Note that in the case there are enough
CRTCs, disabled outputs don't loose it (so there's no modeset
and plane initialization needed after DPMS). CRTC allocation
still prefers to keep the old configuration, even if that means
allocating an extra CRTC to a disabled output.
CRTC reallocation now happen when enabling/disabling an output as
well as when trying to modeset. When enabling an output without a
CRTC, we realloc to try to steal a CRTC from a disabled output
(that doesn't really need the CRTC). When disabling an output, we
try to give our CRTC to an output that needs one. Modesetting is
similar to enabling.
A new DRM connector field has been added: `desired_enabled`.
Outputs without CRTCs get automatically disabled. This field keeps
track of the state desired by the user, allowing to automatically
re-enable outputs when a CRTC becomes free.
This required some changes to the allocation algorithm. Previously,
the algorithm tried to keep the previous configuration even if a
new configuration with a better score was possible (it only changed
configuration when the old one didn't work anymore). This is now
changed and the old configuration (still preferred) is only
retained without considering new possibilities when it's perfect
(all outputs have CRTCs).
User-disabled outputs now have `possible_crtcs` set to 0, meaning
they can only retain a previous CRTC (not acquire a new one). The
allocation algorithm has been updated to do not bump the score
when assigning a CRTC to a disabled output.
This commit handles better situations in which the number of
connected outputs is greater than the number of available CRTCs.
It'll enable as many outputs as possible, and transfer CRTCs to
outputs that need one on unplug.
This changes CRTC and plane reallocation to happen after scanning
DRM connectors instead of on modeset.
This cleanups CRTCs and planes on unplug to allow them to be
re-used for other outputs.
On modeset, if an output doesn't have a CRTC, the desired mode is
saved and used later when the output gains a CRTC.
Future work includes giving priority to enabled outputs over
disabled ones for CRTC allocation. This requires the compositor to
know about all outputs (even outputs without CRTCs) to properly
modeset outputs enabled in the compositor config file and disable
outputs disabled in the config file.
This prevents receiving modesetting requests from the compositor
while we don't have the whole picture (ie. while we haven't yet
scanned all connectors).
This also makes connectors without CRTCs disabled (they can't be
enabled yet even if some CRTCs are free'd -- this is future work).
