drm/kms: add page flipping ioctl

This adds a page flipping ioctl to the KMS API.  The ioctl takes an fb ID
and a ctrc ID and flips the crtc to the given fb at the next vblank.
The ioctl returns immediately but the flip doesn't happen until after
any rendering that's currently queued up against the new framebuffer
is done.  After submitting a page flip, any execbuffer involving the
old front buffer will block until the flip is completed.

Optionally, a vblank event can be generated when the swap eventually
happens.

Signed-off-by: Kristian Høgsberg <krh@bitplanet.net>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/include/drm/drm_mode.h b/include/drm/drm_mode.h
index 1f908416aedb..68ddc6175ae7 100644
--- a/include/drm/drm_mode.h
+++ b/include/drm/drm_mode.h
@@ -268,4 +268,37 @@ struct drm_mode_crtc_lut {
         __u64 blue;
 };
 
+#define DRM_MODE_PAGE_FLIP_EVENT 0x01
+#define DRM_MODE_PAGE_FLIP_FLAGS DRM_MODE_PAGE_FLIP_EVENT
+
+/*
+ * Request a page flip on the specified crtc.
+ *
+ * This ioctl will ask KMS to schedule a page flip for the specified
+ * crtc.  Once any pending rendering targeting the specified fb (as of
+ * ioctl time) has completed, the crtc will be reprogrammed to display
+ * that fb after the next vertical refresh.  The ioctl returns
+ * immediately, but subsequent rendering to the current fb will block
+ * in the execbuffer ioctl until the page flip happens.  If a page
+ * flip is already pending as the ioctl is called, EBUSY will be
+ * returned.
+ *
+ * The ioctl supports one flag, DRM_MODE_PAGE_FLIP_EVENT, which will
+ * request that drm sends back a vblank event (see drm.h: struct
+ * drm_event_vblank) when the page flip is done.  The user_data field
+ * passed in with this ioctl will be returned as the user_data field
+ * in the vblank event struct.
+ *
+ * The reserved field must be zero until we figure out something
+ * clever to use it for.
+ */
+
+struct drm_mode_crtc_page_flip {
+        __u32 crtc_id;
+        __u32 fb_id;
+        __u32 flags;
+        __u32 reserved;
+        __u64 user_data;
+};
+
 #endif