When generating events for a atomic commit involving multiple crtc's it's not possible to distinguish which crtc belongs to which page flip event. Solve this by putting crtc_id in the reserved member of page_flip_event.
I've checked weston, and the following ddx: modesetting (xserver), i915, nouveau, ati, vmwgfx.
None of them depend in any way on the reserved member, so setting it to non-zero should be safe. A lot of them use libdrm, which hides the page flip event struct and only passes its members.
This is why I also changed libdrm to pass crtc_id in page_flip_handler2. Any compositor that uses drmHandleEvent will be able to get information about the crtc_id too, if available.
Maarten Lankhorst (2): (kernel) drm/core: Reuse the reserved member in drm_event_vblank for crtc_id. (libdrm) Add support for crtc_id in page flip events
Kernel: drivers/gpu/drm/drm_irq.c | 2 ++ include/uapi/drm/drm.h | 2 +- 2 files changed, 3 insertions(+), 1 deletion(-)
Libdrm: include/drm/drm.h | 2 +- tests/modetest/modetest.c | 20 ++++++++++++++++++-- xf86drm.h | 16 +++++++++++++++- xf86drmMode.c | 23 ++++++++++++++++------- 4 files changed, 50 insertions(+), 11 deletions(-)