omap: add refcnting and handle tracking

There can be scenarios, especially when re-importing an existing buffer,
where you end up with multiple 'struct omap_bo's wrapping a single GEM
object handle.  Which causes badness when the first of the evil-clones
is omap_bo_del()'d.

To do this, introduce reference counting and a hashtable to track the
handles per fd.

First, to avoid bo's slipping through the crack if multiple 'struct
omap_device's are created for one drm fd, a hashtable mapping drm
fd to omap_device, and the omap_device itself is reference counted.
Per omap_device, we keep a handle_table mapping GEM handle to omap_bo.
When buffers are imported from flink name or dmabuf fd, the handle
table is consulted, and if an omap_bo already exists, it's refcnt is
incremented and it is returned.  For good measure, to avoid the
handle_table being deleted before the omap_bo is freed, the omap_bo
holds a reference to the omap_device.

TODO: check the overhead of the hashtable.  If too much we could maybe
get away with only tracking exported and imported bo's in the table.

TODO: all the import/export flink/dmabuf operations are generic DRM
ioctls.  Really all this functionality could be handled by a generic
drm_bo and drm_device "base class" that could be extended by omap,
exynos, etc.  That would also allow more common userspace code by
avoiding artificial libdrm_omap dependencies.

Signed-off-by: Rob Clark <rob@ti.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/omap/omap_drmif.h b/omap/omap_drmif.h
index 284b9ccc..e62d1278 100644
--- a/omap/omap_drmif.h
+++ b/omap/omap_drmif.h
@@ -38,6 +38,7 @@ struct omap_device;
  */
 
 struct omap_device * omap_device_new(int fd);
+struct omap_device * omap_device_ref(struct omap_device *dev);
 void omap_device_del(struct omap_device *dev);
 int omap_get_param(struct omap_device *dev, uint64_t param, uint64_t *value);
 int omap_set_param(struct omap_device *dev, uint64_t param, uint64_t value);
@@ -49,6 +50,7 @@ struct omap_bo * omap_bo_new(struct omap_device *dev,
 		uint32_t size, uint32_t flags);
 struct omap_bo * omap_bo_new_tiled(struct omap_device *dev,
 		uint32_t width, uint32_t height, uint32_t flags);
+struct omap_bo * omap_bo_ref(struct omap_bo *bo);
 struct omap_bo * omap_bo_from_name(struct omap_device *dev, uint32_t name);
 struct omap_bo * omap_bo_from_dmabuf(struct omap_device *dev, int fd);
 void omap_bo_del(struct omap_bo *bo);