diff mbox

[1/3] drm: Update GEM refcounting docs

Message ID 1445533889-7661-1-git-send-email-daniel.vetter@ffwll.ch
State New, archived
Headers show

Commit Message

Daniel Vetter Oct. 22, 2015, 5:11 p.m. UTC
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>
---
 Documentation/DocBook/gpu.tmpl |  15 +++---
 include/drm/drm_gem.h          | 106 +++++++++++++++++++++++++++++++++++------
 2 files changed, 100 insertions(+), 21 deletions(-)

Comments

Alex Deucher Oct. 22, 2015, 5:54 p.m. UTC | #1
On Thu, Oct 22, 2015 at 1:11 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> 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>

Patches 1 and 3 are:
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

> ---
>  Documentation/DocBook/gpu.tmpl |  15 +++---
>  include/drm/drm_gem.h          | 106 +++++++++++++++++++++++++++++++++++------
>  2 files changed, 100 insertions(+), 21 deletions(-)
>
> diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> index 90c2aab31269..6c5865bb5ee8 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)
>  {
> --
> 2.5.1
>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/dri-devel
Daniel Vetter Oct. 22, 2015, 7:46 p.m. UTC | #2
On Thu, Oct 22, 2015 at 01:54:17PM -0400, Alex Deucher wrote:
> On Thu, Oct 22, 2015 at 1:11 PM, Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > 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>
> 
> Patches 1 and 3 are:
> Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

Thanks, applied to drm-misc.
-Daniel

> 
> > ---
> >  Documentation/DocBook/gpu.tmpl |  15 +++---
> >  include/drm/drm_gem.h          | 106 +++++++++++++++++++++++++++++++++++------
> >  2 files changed, 100 insertions(+), 21 deletions(-)
> >
> > diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
> > index 90c2aab31269..6c5865bb5ee8 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)
> >  {
> > --
> > 2.5.1
> >
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/dri-devel
diff mbox

Patch

diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl
index 90c2aab31269..6c5865bb5ee8 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)
 {