drm: Update GEM refcounting docs

I just realized that I've forgotten to update all the gem refcounting
docs. For pennance also add pretty docs for the overall drm_gem_object
structure, with a few links thrown in fore good.

As usually we need to make sure the kerneldoc reference is at most a
sect2 for otherwise it won't be listed.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1445533889-7661-1-git-send-email-daniel.vetter@ffwll.ch
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Documentation/DocBook/gpu.tmpl

@@ -635,10 +635,10 @@ char *date;</synopsis>
           acquired and release by <function>calling drm_gem_object_reference</function>
           and <function>drm_gem_object_unreference</function> respectively. The
           caller must hold the <structname>drm_device</structname>
-          <structfield>struct_mutex</structfield> lock. As a convenience, GEM
-          provides the <function>drm_gem_object_reference_unlocked</function> and
-          <function>drm_gem_object_unreference_unlocked</function> functions that
-          can be called without holding the lock.
+	  <structfield>struct_mutex</structfield> lock when calling
+	  <function>drm_gem_object_reference</function>. As a convenience, GEM
+	  provides <function>drm_gem_object_unreference_unlocked</function>
+	  functions that can be called without holding the lock.
         </para>
         <para>
           When the last reference to a GEM object is released the GEM core calls
@@ -836,10 +836,11 @@ char *date;</synopsis>
           abstracted from the client in libdrm.
         </para>
       </sect3>
-      <sect3>
-        <title>GEM Function Reference</title>
+    </sect2>
+    <sect2>
+      <title>GEM Function Reference</title>
 !Edrivers/gpu/drm/drm_gem.c
-      </sect3>
+!Iinclude/drm/drm_gem.h
     </sect2>
     <sect2>
       <title>VMA Offset Manager</title>

include/drm/drm_gem.h

@@ -35,76 +35,129 @@
  */
 
 /**
- * This structure defines the drm_mm memory object, which will be used by the
- * DRM for its buffer objects.
+ * struct drm_gem_object - GEM buffer object
+ *
+ * This structure defines the generic parts for GEM buffer objects, which are
+ * mostly around handling mmap and userspace handles.
+ *
+ * Buffer objects are often abbreviated to BO.
  */
 struct drm_gem_object {
-	/** Reference count of this object */
+	/**
+	 * @refcount:
+	 *
+	 * Reference count of this object
+	 *
+	 * Please use drm_gem_object_reference() to acquire and
+	 * drm_gem_object_unreference() or drm_gem_object_unreference_unlocked()
+	 * to release a reference to a GEM buffer object.
+	 */
 	struct kref refcount;
 
 	/**
-	 * handle_count - gem file_priv handle count of this object
+	 * @handle_count:
+	 *
+	 * This is the GEM file_priv handle count of this object.
 	 *
 	 * Each handle also holds a reference. Note that when the handle_count
 	 * drops to 0 any global names (e.g. the id in the flink namespace) will
 	 * be cleared.
 	 *
 	 * Protected by dev->object_name_lock.
-	 * */
+	 */
 	unsigned handle_count;
 
-	/** Related drm device */
+	/**
+	 * @dev: DRM dev this object belongs to.
+	 */
 	struct drm_device *dev;
 
-	/** File representing the shmem storage */
+	/**
+	 * @filp:
+	 *
+	 * SHMEM file node used as backing storage for swappable buffer objects.
+	 * GEM also supports driver private objects with driver-specific backing
+	 * storage (contiguous CMA memory, special reserved blocks). In this
+	 * case @filp is NULL.
+	 */
 	struct file *filp;
 
-	/* Mapping info for this object */
+	/**
+	 * @vma_node:
+	 *
+	 * Mapping info for this object to support mmap. Drivers are supposed to
+	 * allocate the mmap offset using drm_gem_create_mmap_offset(). The
+	 * offset itself can be retrieved using drm_vma_node_offset_addr().
+	 *
+	 * Memory mapping itself is handled by drm_gem_mmap(), which also checks
+	 * that userspace is allowed to access the object.
+	 */
 	struct drm_vma_offset_node vma_node;
 
 	/**
+	 * @size:
+	 *
 	 * Size of the object, in bytes.  Immutable over the object's
 	 * lifetime.
 	 */
 	size_t size;
 
 	/**
+	 * @name:
+	 *
 	 * Global name for this object, starts at 1. 0 means unnamed.
-	 * Access is covered by the object_name_lock in the related drm_device
+	 * Access is covered by dev->object_name_lock. This is used by the GEM_FLINK
+	 * and GEM_OPEN ioctls.
 	 */
 	int name;
 
 	/**
-	 * Memory domains. These monitor which caches contain read/write data
+	 * @read_domains:
+	 *
+	 * Read memory domains. These monitor which caches contain read/write data
 	 * related to the object. When transitioning from one set of domains
 	 * to another, the driver is called to ensure that caches are suitably
-	 * flushed and invalidated
+	 * flushed and invalidated.
 	 */
 	uint32_t read_domains;
+
+	/**
+	 * @write_domain: Corresponding unique write memory domain.
+	 */
 	uint32_t write_domain;
 
 	/**
+	 * @pending_read_domains:
+	 *
 	 * While validating an exec operation, the
 	 * new read/write domain values are computed here.
 	 * They will be transferred to the above values
 	 * at the point that any cache flushing occurs
 	 */
 	uint32_t pending_read_domains;
+
+	/**
+	 * @pending_write_domain: Write domain similar to @pending_read_domains.
+	 */
 	uint32_t pending_write_domain;
 
 	/**
-	 * dma_buf - dma buf associated with this GEM object
+	 * @dma_buf:
+	 *
+	 * dma-buf associated with this GEM object.
 	 *
 	 * Pointer to the dma-buf associated with this gem object (either
 	 * through importing or exporting). We break the resulting reference
 	 * loop when the last gem handle for this object is released.
 	 *
-	 * Protected by obj->object_name_lock
+	 * Protected by obj->object_name_lock.
 	 */
 	struct dma_buf *dma_buf;
 
 	/**
-	 * import_attach - dma buf attachment backing this object
+	 * @import_attach:
+	 *
+	 * dma-buf attachment backing this object.
 	 *
 	 * Any foreign dma_buf imported as a gem object has this set to the
 	 * attachment point for the device. This is invariant over the lifetime
@@ -133,12 +186,30 @@ int drm_gem_mmap_obj(struct drm_gem_object *obj, unsigned long obj_size,
 		     struct vm_area_struct *vma);
 int drm_gem_mmap(struct file *filp, struct vm_area_struct *vma);
 
+/**
+ * drm_gem_object_reference - acquire a GEM BO reference
+ * @obj: GEM buffer object
+ *
+ * This acquires additional reference to @obj. It is illegal to call this
+ * without already holding a reference. No locks required.
+ */
 static inline void
 drm_gem_object_reference(struct drm_gem_object *obj)
 {
 	kref_get(&obj->refcount);
 }
 
+/**
+ * drm_gem_object_unreference - release a GEM BO reference
+ * @obj: GEM buffer object
+ *
+ * This releases a reference to @obj. Callers must hold the dev->struct_mutex
+ * lock when calling this function, even when the driver doesn't use
+ * dev->struct_mutex for anything.
+ *
+ * For drivers not encumbered with legacy locking use
+ * drm_gem_object_unreference_unlocked() instead.
+ */
 static inline void
 drm_gem_object_unreference(struct drm_gem_object *obj)
 {
@@ -149,6 +220,13 @@ drm_gem_object_unreference(struct drm_gem_object *obj)
 	}
 }
 
+/**
+ * drm_gem_object_unreference_unlocked - release a GEM BO reference
+ * @obj: GEM buffer object
+ *
+ * This releases a reference to @obj. Callers must not hold the
+ * dev->struct_mutex lock when calling this function.
+ */
 static inline void
 drm_gem_object_unreference_unlocked(struct drm_gem_object *obj)
 {