Currently, there's nothing actually stopping a driver from only registering
vblank support for some of it's CRTCs and not for others. As far as I can
tell, this isn't really defined behavior on the C side of things - as the
documentation explicitly mentions to not use drm_vblank_init() if you don't
have vblank support - since DRM then steps in and adds its own vblank
emulation implementation.
So, let's fix this edge case and check to make sure it's all or none.
Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
Fixes: 3ed4351a83ca ("drm: Extract drm_vblank.[hc]")
Cc: Stefan Agner <stefan@xxxxxxxx>
Cc: Daniel Vetter <daniel.vetter@xxxxxxxxx>
Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Cc: Maxime Ripard <mripard@xxxxxxxxxx>
Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: David Airlie <airlied@xxxxxxxxx>
Cc: Simona Vetter <simona@xxxxxxxx>
Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
Cc: <stable@xxxxxxxxxxxxxxx> # v4.13+
---
drivers/gpu/drm/drm_vblank.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 94e45ed6869d0..4d00937e8ca2e 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -525,9 +525,19 @@ static void drm_vblank_init_release(struct drm_device *dev, void *ptr)
*/
int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
{
+ struct drm_crtc *crtc;
int ret;
unsigned int i;
+ // Confirm that the required vblank functions have been filled out for all CRTCS
+ drm_for_each_crtc(crtc, dev) {
+ if (!crtc->funcs->enable_vblank || !crtc->funcs->disable_vblank) {
+ drm_err(dev, "CRTC vblank functions not initialized for %s, abort\n",
+ crtc->name);
+ return -EINVAL;
+ }
+ }
+
spin_lock_init(&dev->vbl_lock);
spin_lock_init(&dev->vblank_time_lock);
base-commit: 22512c3ee0f47faab5def71c4453638923c62522
--
2.46.1
