On Fri, Dec 04, 2015 at 09:46:09AM +0100, Daniel Vetter wrote:
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.
Cc: Daniel Stone daniels@collabora.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch
drivers/gpu/drm/drm_atomic.c | 9 +++++++++ drivers/gpu/drm/drm_atomic_helper.c | 8 ++++++++ 2 files changed, 17 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c index 7426d40017a0..06cdb52907da 100644 --- a/drivers/gpu/drm/drm_atomic.c +++ b/drivers/gpu/drm/drm_atomic.c @@ -1265,6 +1265,15 @@ int drm_atomic_check_only(struct drm_atomic_state *state) if (config->funcs->atomic_check) ret = config->funcs->atomic_check(state->dev, state);
- /*
* 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* compositors drawing loop. This is consistent with the vblank ioctl
"compositor's".
* which also rejects service on a disabled pipe.*/diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c index 110f3db8dd05..8e281a96c35f 100644 --- a/drivers/gpu/drm/drm_atomic_helper.c +++ b/drivers/gpu/drm/drm_atomic_helper.c @@ -2283,6 +2283,14 @@ retry: goto fail; drm_atomic_set_fb_for_plane(plane_state, fb);
- state->allow_modeset = false;
Perhaps explain the reason for setting this?
Thierry