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Commit 4cba6850 authored by Daniel Vetter's avatar Daniel Vetter
Browse files

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: default avatarDaniel Stone <daniels@collabora.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1449564561-3896-4-git-send-email-daniel.vetter@ffwll.ch
parent 4cd9fa52

drivers/gpu/drm/drm_atomic.c

+16 −0
Original line number Diff line number Diff line
@@ -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;

}

drivers/gpu/drm/drm_atomic_helper.c

+9 −0
Original line number Diff line number Diff line
@@ -2284,6 +2284,15 @@ int drm_atomic_helper_page_flip(struct drm_crtc *crtc, 
		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;

include/drm/drm_crtc.h

+2 −1
Original line number Diff line number Diff line
@@ -551,7 +551,8 @@ 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,