drm/atomic: Reject events for inactive crtc's.

[Maarten Lankhorst]

This will cause drm_atomic_helper_page_flip and drm_mode_atomic_ioctl to
fail with -EINVAL if a event is requested on a inactive crtc.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
---
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index d719ce0b10a0..679577e8e02d 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -476,6 +476,12 @@ static int drm_atomic_crtc_check(struct drm_crtc *crtc,
 		return -EINVAL;
 	}
 
+	if (!state->active && state->event) {
+		DRM_DEBUG_ATOMIC("[CRTC:%d] requesting event and not active\n",
+				 crtc->base.id);
+		return -EINVAL;
+	}
+
 	/* The state->enable vs. state->mode_blob checks can be WARN_ON,
 	 * as this is a kernel-internal detail that userspace should never
 	 * be able to trigger. */