Historically drm lacked fb refcounting, so the updating of crtc->fb was done by the lower levels at a point convenient to get their own refcounting (e.g. refcounts for the underlying gem bo, pinning refcounts) right. With the introduction of refcounted fbs the drm core handled the fb refcounts, but still relied on drivers to update the crtc->fb pointer (this approach required the least invasive changes in drivers).
Enforce this contract with a WARN_ON.
Signed-off-by: Daniel Vetter daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_crtc.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c index baee575..bcee25a 100644 --- a/drivers/gpu/drm/drm_crtc.c +++ b/drivers/gpu/drm/drm_crtc.c @@ -1939,6 +1939,9 @@ int drm_mode_set_config_internal(struct drm_mode_set *set)
ret = crtc->funcs->set_config(set); if (ret == 0) { + /* crtc->fb must be updated by ->set_config, enforces this. */ + WARN_ON(fb != crtc->fb); + if (old_fb) drm_framebuffer_unreference(old_fb); if (fb)