We want this for consistency with existing page_flip semantics.
Since this spurred quite a discussion on IRC also document why we
reject even generation when the pipe is off: It's not that it's hard
to implement, but userspace has a track recording proofing 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@xxxxxxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxx>
---
drivers/gpu/drm/drm_atomic.c | 16 ++++++++++++++++
drivers/gpu/drm/drm_atomic_helper.c | 9 +++++++++
include/drm/drm_crtc.h | 3 ++-
3 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 07ab75e22b2b..029377513b1d 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -508,6 +508,22 @@ static int drm_atomic_crtc_check(struct drm_crtc *crtc,
return -EINVAL;
}
+ /*
+ * Reject event generation for when a CRTC is off and stays off.
+ * It wouldn't be hard to implement this, but userspace has a track
+ * record of happily burning through 100% cpu (or worse, crash) when the
+ * display pipe is suspended. To avoid all that fun just reject updates
+ * that ask for events since likely that indicates a bug in the
+ * compositor's drawing loop. This is consistent with the vblank IOCTL
+ * and legacy page_flip IOCTL which also reject service on a disabled
+ * pipe.
+ */
+ if (state->event && !state->active && !crtc->state->active) {
+ DRM_DEBUG_ATOMIC("[CRTC:%d] requesting event but off\n",
+ crtc->base.id);
+ return -EINVAL;
+ }
+
return 0;
}
diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 76c124b2a775..9eb367cad790 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -2282,6 +2282,15 @@ retry:
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;
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index 6fe14a773def..6da847a6cb2f 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -548,7 +548,8 @@ struct drm_crtc_funcs {
* ->page_flip() operation is already pending the callback should return
* -EBUSY. Pageflips on a disabled CRTC (either by setting a NULL mode
* or just runtime disabled through DPMS respectively the new atomic
- * "ACTIVE" state) should result in an -EINVAL error code.
+ * "ACTIVE" state) should result in an -EINVAL error code. Note that
+ * drm_atomic_helper_page_flip() checks this already for atomic drivers.
*/
int (*page_flip)(struct drm_crtc *crtc,
struct drm_framebuffer *fb,
--
2.5.1
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