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>

2 files changed, 100 insertions, 21 deletions

diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
index 201dcd3c2e9d..47b06dfa454d 100644
--- a/Documentation/DocBook/gpu.tmpl
+++ b/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>
diff --git a/include/drm/drm_gem.h b/include/drm/drm_gem.h
index 15e7f007380f..0b3e11ab8757 100644
--- a/include/drm/drm_gem.h
+++ b/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)
 {