drm/atomic-helper: Reject legacy flips on a disabled pipe
We want this for consistency with existing page_flip semantics.
Since this spurred quite a discussion on IRC also document why we
reject event generation when the pipe is off: It's not that it's hard
to implement, but userspace has a track recording which proves that it's
way too easy to accidentally abuse and cause havoc. We want to make
sure userspace doesn't get away with that.
v2: Somehow thought we do reject events already, but that code only
existed in my imagination ... Also suggestions from Thierry.
Cc: Daniel Stone <daniels@collabora.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Thierry Reding <thierry.reding@gmail.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449564561-3896-4-git-send-email-daniel.vetter@ffwll.ch
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 26d258d..738104b 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -2284,6 +2284,15 @@
goto fail;
drm_atomic_set_fb_for_plane(plane_state, fb);
+ /* Make sure we don't accidentally do a full modeset. */
+ state->allow_modeset = false;
+ if (!crtc_state->active) {
+ DRM_DEBUG_ATOMIC("[CRTC:%d] disabled, rejecting legacy flip\n",
+ crtc->base.id);
+ ret = -EINVAL;
+ goto fail;
+ }
+
ret = drm_atomic_async_commit(state);
if (ret != 0)
goto fail;