There were fallbacks in place in case IN_FORMATS didn't yield any usable
formats: the formats in the drmModePlane struct, and a hard coded array.
The lack of these fallbacks in place could result in a segfault as code
using the supported plane formats assumed there were at least something
in there.
https://gitlab.gnome.org/GNOME/mutter/merge_requests/662
This commit introduces, and makes use of, a transactional API used for
setting up KMS state, later to be applied, potentially atomically. From
an API point of view, so is always the case, but in the current
implementation, it still uses legacy drmMode* API to apply the state
non-atomically.
The API consists of various buliding blocks:
* MetaKmsUpdate - a set of configuration changes, the higher level
handle for handing over configuration to the impl backend. It's used to
set mode, assign framebuffers to planes, queue page flips and set
connector properties.
* MetaKmsPlaneAssignment - the assignment of a framebuffer to a plane.
Currently used to map a framebuffer to the primary plane of a CRTC. In
the legacy KMS implementation, the plane assignment is used to derive
the framebuffer used for mode setting and page flipping.
This also means various high level changes:
State, excluding configuring the cursor plane and creating/destroying
DRM framebuffer handles, are applied in the end of a clutter frame, in
one go. From an API point of view, this is done atomically, but as
mentioned, only the non-atomic implementation exists so far.
From MetaRendererNative's point of view, a page flip now initially
always succeeds; the handling of EBUSY errors are done asynchronously in
the MetaKmsImpl backend (still by retrying at refresh rate, but
postponing flip callbacks instead of manipulating the frame clock).
Handling of falling back to mode setting instead of page flipping is
notified after the fact by a more precise page flip feedback API.
EGLStream based page flipping relies on the impl backend not being
atomic, as the page flipping is done in the EGLStream backend (e.g.
nvidia driver). It uses a 'custom' page flip queueing method, keeping
the EGLStream logic inside meta-renderer-native.c.
Page flip handling is moved to meta-kms-impl-device.c from
meta-gpu-kms.c. It goes via an extra idle callback before reaching
meta-renderer-native.c to make sure callbacks are invoked outside of the
impl context.
While dummy power save page flipping is kept in meta-renderer-native.c, the
EBUSY handling is moved to meta-kms-impl-simple.c. Instead of freezing the
frame clock, actual page flip callbacks are postponed until all EBUSY retries
have either succeeded or failed due to some other error than EBUSY. This
effectively inhibits new frames to be drawn, meaning we won't stall waiting on
the file descriptor for pending page flips.
https://gitlab.gnome.org/GNOME/mutter/issues/548https://gitlab.gnome.org/GNOME/mutter/merge_requests/525
A plane is one of three possible: primary, overlay and cursor. Each
plane can have various properties, such as possible rotations, formats
etc. Each plane can also be used with a set of CRTCs.
A primary plane is the "backdrop" of a CRTC, i.e. the primary output for
the composited frame that covers the whole CRTC. In general, mutter
composites to a stage view frame onto a framebuffer that is then put on
the primary plane.
An overlay plane is a rectangular area that can be displayed on top of
the primary plane. Eventually it will be used to place non-fullscreen
surfaces, potentially avoiding stage redraws.
A cursor plane is a plane placed on top of all the other planes, usually
used to put the mouse cursor sprite.
Initially, we only fetch the rotation properties, and we so far
blacklist all rotations except ones that ends up with the same
dimensions as with no rotations. This is because non-180° rotations
doesn't work yet due to incorrect buffer modifiers. To make it possible
to use non-180° rotations, changes necessary include among other things
finding compatible modifiers using atomic modesetting. Until then,
simply blacklist the ones we know doesn't work.
https://gitlab.gnome.org/GNOME/mutter/issues/548https://gitlab.gnome.org/GNOME/mutter/merge_requests/525
