drm: refcnt drm_framebuffer (v4.1)
This simplifies drm fb lifetime, and if the crtc/plane needs to hold
a ref to the fb when disabling a pipe until the next vblank, this
avoids the need to make disabling an overlay synchronous. This is a
problem that shows up when userspace is using a drm plane to
implement a hw cursor.. making overlay disable synchronous causes
a performance problem when x11 is rapidly enabling/disabling the
hw cursor. But not making it synchronous opens up a race condition
for crashing if userspace turns around and immediately deletes the
fb. Refcnt'ing the fb makes it possible to solve this problem.
v1: original
v2: add drm_framebuffer_remove() which is called in all paths where
fb->funcs->destroy() was directly called before. This cleans
up the CRTCs/planes that the fb was attached to. You should
only directly use drm_framebuffer_unreference() if you are also
using drm_framebuffer_reference() to keep a ref to the fb.
v3: add comment explaining the fb refcount
v4: remove duplicate 'list_del(&fb->filp_head)'
[airlied: v4.1: fix local rejection]
Signed-off-by: Rob Clark <rob@ti.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/include/drm/drm_crtc.h b/include/drm/drm_crtc.h
index eb91d52..68fdb29 100644
--- a/include/drm/drm_crtc.h
+++ b/include/drm/drm_crtc.h
@@ -218,6 +218,7 @@
};
struct drm_framebuffer_funcs {
+ /* note: use drm_framebuffer_remove() */
void (*destroy)(struct drm_framebuffer *framebuffer);
int (*create_handle)(struct drm_framebuffer *fb,
struct drm_file *file_priv,
@@ -242,6 +243,16 @@
struct drm_framebuffer {
struct drm_device *dev;
+ /*
+ * Note that the fb is refcounted for the benefit of driver internals,
+ * for example some hw, disabling a CRTC/plane is asynchronous, and
+ * scanout does not actually complete until the next vblank. So some
+ * cleanup (like releasing the reference(s) on the backing GEM bo(s))
+ * should be deferred. In cases like this, the driver would like to
+ * hold a ref to the fb even though it has already been removed from
+ * userspace perspective.
+ */
+ struct kref refcount;
struct list_head head;
struct drm_mode_object base;
const struct drm_framebuffer_funcs *funcs;
@@ -919,6 +930,9 @@
extern int drm_framebuffer_init(struct drm_device *dev,
struct drm_framebuffer *fb,
const struct drm_framebuffer_funcs *funcs);
+extern void drm_framebuffer_unreference(struct drm_framebuffer *fb);
+extern void drm_framebuffer_reference(struct drm_framebuffer *fb);
+extern void drm_framebuffer_remove(struct drm_framebuffer *fb);
extern void drm_framebuffer_cleanup(struct drm_framebuffer *fb);
extern int drmfb_probe(struct drm_device *dev, struct drm_crtc *crtc);
extern int drmfb_remove(struct drm_device *dev, struct drm_framebuffer *fb);