Cursor planes are a bit trickier to support via the universal plane interface than primary planes were. Legacy cursor ioctls take handles to driver buffers directly whereas the universal plane API takes drm_framebuffer's that represent a buffer; due to this mismatch it isn't possible to implement a set of cursor helpers than provide "free" generic universal cursor support without driver changes as we did with primary planes. Drivers will need to be updated to receive cursor support via the universal plane API.
If a driver tries to implement two interfaces for cursor support (legacy ioctl and universal planes), the reference counting can get very tricky/messy since we need to take into account userspace that may mix and match calls to both interfaces. To address that, patch #1 in this set causes legacy cursor ioctls to be implemented using a driver's universal plane support if the driver registers a primary plane. Calls to the legacy set_cursor ioctl will wrap the provided driver buffer in a drm_framebuffer and then pass that along to the universal plane interface. From a driver's point of view, this causes all cursor operations to arrive on the universal plane interface, regardless of which userspace API was used, which simplifies things greatly for the driver.
Patch #2 makes some minor changes to ensure drivers can successfully register a cursor plane with the DRM core.
Patch #3 does some minor i915 refactoring in preparation for the move to universal planes.
Patch #4 transitions the i915 driver to universal planes. The changes here are intentionally minimal for ease of review. It's likely that we could perform further cleanup in the future to eliminate some of the cursor state tracked in intel_crtc (e.g., cursor_width/cursor_height) since that information can be also be derived from crtc->cursor->fb.
Matt Roper (4): drm: Support legacy cursor ioctls via universal planes when possible drm: Allow drivers to register cursor planes with crtc drm/i915: Add intel_crtc_cursor_set_obj() to set cursor buffer drm/i915: Switch to unified plane cursor handling
drivers/gpu/drm/drm_crtc.c | 113 ++++++++++++++++++++- drivers/gpu/drm/i915/intel_display.c | 188 ++++++++++++++++++++++++++++------- drivers/gpu/drm/i915/intel_drv.h | 1 - include/drm/drm_crtc.h | 6 +- 4 files changed, 267 insertions(+), 41 deletions(-)