diff options
| -rw-r--r-- | Documentation/DocBook/drm.tmpl | 6 | ||||
| -rw-r--r-- | drivers/gpu/drm/drm_crtc.c | 7 |
2 files changed, 13 insertions, 0 deletions
diff --git a/Documentation/DocBook/drm.tmpl b/Documentation/DocBook/drm.tmpl index 51e1904ac4c7..a6428ddfcfc2 100644 --- a/Documentation/DocBook/drm.tmpl +++ b/Documentation/DocBook/drm.tmpl @@ -1161,6 +1161,12 @@ int max_width, max_height;</synopsis> any new rendering to the frame buffer until the page flip completes. </para> <para> + If a page flip can be successfully scheduled the driver must set the + <code>drm_crtc-<fb</code> field to the new framebuffer pointed to + by <code>fb</code>. This is important so that the reference counting + on framebuffers stays balanced. + </para> + <para> If a page flip is already pending, the <methodname>page_flip</methodname> operation must return -<errorname>EBUSY</errorname>. diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index 781aef524b3b..3bdf2a650d9c 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -3792,6 +3792,13 @@ int drm_mode_page_flip_ioctl(struct drm_device *dev, /* Keep the old fb, don't unref it. */ old_fb = NULL; } else { + /* + * Warn if the driver hasn't properly updated the crtc->fb + * field to reflect that the new framebuffer is now used. + * Failing to do so will screw with the reference counting + * on framebuffers. + */ + WARN_ON(crtc->fb != fb); /* Unref only the old framebuffer. */ fb = NULL; } |