The previous fix tried to side-step cursor->pending_fb completely.
However that messes up our buffer locking mechanism.
Instead, stop clearing the pending cursor FB on a failed commit. The
pending cursor FB will remain for the next commit.
Fixes: 6c3d080e25 ("backend/drm: populate cursor plane's current_fb")
This reverts commit 6c3d080e25.
Populating wlr_drm_plane.current_fb messes up the buffer's locking.
The previous buffer is released while it's still being displayed
on-screen.
Custom backends and renderers need to implement
wlr_backend_impl.get_buffer_caps and
wlr_renderer_impl.get_render_buffer_caps. They can't if enum
wlr_buffer_cap isn't made public.
Right now, when a new output state field is added, all backends by
default won't reject it. This means we need to add new checks to
each and every backend when we introduce a new state field.
Instead, introduce a bitmask of supported output state fields in
each backend, and error out if the user has submitted an unknown
field.
Some fields don't need any backend involvment to work. These are
listed in WLR_OUTPUT_STATE_BACKEND_OPTIONAL as a convenience.
This moves the magic incantation into libdrm and is clearer. See
[1] for details.
While at it, fixup the doc comment and improve logging.
[1]: 523b3658aa
The set_cursor() hook is a little bit special: it's not really
synchronized to commit() or test(). Once set_cursor() returns true,
the new cursor is part of the current state.
This fixes a state where wlr_drm_connector.cursor_enabled is true
but there is no FB available. This is triggered by set_cursor()
followed by a failed commit(), which resets pending_fb.
We should definitely fix the output interface to make the cursor part
of the pending state, but that's a more involved change.
Instead of trying to perform a real modeset in init_renderer,
perform an atomic test-only commit to find out whether disabling
modifiers is necessary because of bandwidth limitations.
This decouples init_renderer from the actual commit, making it
possible to modeset an output with a user-supplied buffer instead
of a black frame.
We loose the ability to make sure the buffers coming from the
swapchain will work fine when using the legacy interface. This
can break i915 when atomic is disabled and modifiers enabled.
But i915 always has atomic (so the user must explicitly disable it
to run into potential bandwidth limitations) and is the only known
problematic driver.
Rely on wlr_output's generic swapchain support instead of creating our
own. The headless output now simply keeps a reference to the front buffer
and does nothing else.
Instead of passing a wlr_texture to the backend, directly pass a
wlr_buffer. Use get_cursor_size and get_cursor_formats to create
a wlr_buffer that can be used as a cursor.
We don't want to pass a wlr_texture because we want to remove as
many rendering bits from the backend as possible.
When picking a format, the backend needs to know whether the
buffers allocated by the allocator will be DMA-BUFs or shared
memory. So far, the backend used the renderer's supported
buffer types to guess this information.
This is pretty fragile: renderers in general don't care about the
SHM cap (they only care about the DATA_PTR one). Additionally,
nothing stops a renderer from supporting both DMA-BUFs and shared
memory, but this would break the backend's guess.
Instead, use wlr_allocator.buffer_caps. This is more reliable since
the buffers created with the allocator are guaranteed to have these
caps.
Instead of managing our own renderer and allocator, let the common
code do it.
Because wlr_headless_backend_create_with_renderer needs to re-use
the parent renderer, we have to hand-roll some of the renderer
initialization.
This new functions cleans up the common backend state. While this
currently only emits the destroy signal, this will also clean up
the renderer and allocator in upcoming patches.
Backend-initiated mode changes can use this function instead of
going through drm_connector_set_mode. drm_connector_set_mode becomes
a mere drm_connector_commit_state helper.
