Only disable planes we can make use of.
Disabling other planes causes same noise and failures if the plane
is still being used on another CRTC.
One motivation for disabling all planes may be to potentially get
more bandwidth to work with. However, we can only increase the
avilable bandwidth by disabling previously enabled planes. KMS will
refuse to switch a plane's CRTC without completely disabling it
first.
When the caller wants to perform a modeset, they will need to pass
DRM_MODE_ATOMIC_ALLOW_MODESET in the atomic commit flags, otherwise the driver
will fail the commit. libliftoff also needs to provide these flags in its
test-only commits.
On debug verbosity logging every reuse of planes is spamming the log making it
difficult to debug the process.
With this patch only the change of reusing the same allocation is logged and
how often the allocation was reused after this changed back again.
Compositors need to drive multiple connectors, each with its own vblank timings.
For each device, there's one separate rendering loop per output.
It's not possible to call liftoff_device_apply each time we want to submit a new
frame to one output, because this could touch another's output state, submitting
a new frame there in the process. When the other output will submit a new frame,
it'll get EBUSY (can't submit two frames without waiting for vblank).
Closes: https://github.com/emersion/libliftoff/issues/21
Start from scratch since we may be able to come up with a better allocation
(if the layer made another layer fall back to composition for instance).
Closes: https://github.com/emersion/libliftoff/issues/30
Keep track of the number of layer updates per 60 page-flips.
We could implement a more fine-grained tracking, for instance with a sliding
window. However it's a lot more complex than the current solution and the gains
are not clear. I'd prefer to keep the current solution and experiment with other
solutions once we have a good test-bed.
References: https://github.com/emersion/libliftoff/issues/22
