drm: Introduce drm_mode_object_{get,put}()

For consistency with other reference counting APIs in the kernel, add
drm_mode_object_get() and drm_mode_object_put() to reference count DRM
mode objects.

Compatibility aliases are added to keep existing code working. To help
speed up the transition, all the instances of the old functions in the
DRM core are already replaced in this commit.

A semantic patch is provided that can be used to convert all drivers to
the new helpers.

Reviewed-by: Sean Paul <[e-mail]>
Acked-by: Christian König <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_atomic.c

···
 		}
 
 		if (!obj->properties) {
-			drm_mode_object_unreference(obj);
+			drm_mode_object_put(obj);
 			ret = -ENOENT;
 			goto out;
 		}
 
 		if (get_user(count_props, count_props_ptr + copied_objs)) {
-			drm_mode_object_unreference(obj);
+			drm_mode_object_put(obj);
 			ret = -EFAULT;
 			goto out;
 		}
···
 			struct drm_property *prop;
 
 			if (get_user(prop_id, props_ptr + copied_props)) {
-				drm_mode_object_unreference(obj);
+				drm_mode_object_put(obj);
 				ret = -EFAULT;
 				goto out;
 			}
 
 			prop = drm_mode_obj_find_prop_id(obj, prop_id);
 			if (!prop) {
-				drm_mode_object_unreference(obj);
+				drm_mode_object_put(obj);
 				ret = -ENOENT;
 				goto out;
 			}
···
 			if (copy_from_user(&prop_value,
 					   prop_values_ptr + copied_props,
 					   sizeof(prop_value))) {
-				drm_mode_object_unreference(obj);
+				drm_mode_object_put(obj);
 				ret = -EFAULT;
 				goto out;
 			}
 
 			ret = atomic_set_prop(state, obj, prop, prop_value);
 			if (ret) {
-				drm_mode_object_unreference(obj);
+				drm_mode_object_put(obj);
 				goto out;
 			}
 
···
 			plane_mask |= (1 << drm_plane_index(plane));
 			plane->old_fb = plane->fb;
 		}
-		drm_mode_object_unreference(obj);
+		drm_mode_object_put(obj);
 	}
 
 	ret = prepare_crtc_signaling(dev, state, arg, file_priv, &fence_state,

drivers/gpu/drm/drm_mode_object.c

···
  *
  * This function is used to look up a modeset object. It will acquire a
  * reference for reference counted objects. This reference must be dropped again
- * by callind drm_mode_object_unreference().
+ * by callind drm_mode_object_put().
  */
 struct drm_mode_object *drm_mode_object_find(struct drm_device *dev,
 		uint32_t id, uint32_t type)
···
 EXPORT_SYMBOL(drm_mode_object_find);
 
 /**
- * drm_mode_object_unreference - decr the object refcnt
- * @obj: mode_object
+ * drm_mode_object_put - release a mode object reference
+ * @obj: DRM mode object
  *
  * This function decrements the object's refcount if it is a refcounted modeset
  * object. It is a no-op on any other object. This is used to drop references
- * acquired with drm_mode_object_reference().
+ * acquired with drm_mode_object_get().
  */
-void drm_mode_object_unreference(struct drm_mode_object *obj)
+void drm_mode_object_put(struct drm_mode_object *obj)
 {
 	if (obj->free_cb) {
 		DRM_DEBUG("OBJ ID: %d (%d)\n", obj->id, atomic_read(&obj->refcount.refcount));
 		kref_put(&obj->refcount, obj->free_cb);
 	}
 }
-EXPORT_SYMBOL(drm_mode_object_unreference);
+EXPORT_SYMBOL(drm_mode_object_put);
 
 /**
- * drm_mode_object_reference - incr the object refcnt
- * @obj: mode_object
+ * drm_mode_object_get - acquire a mode object reference
+ * @obj: DRM mode object
  *
  * This function increments the object's refcount if it is a refcounted modeset
  * object. It is a no-op on any other object. References should be dropped again
- * by calling drm_mode_object_unreference().
+ * by calling drm_mode_object_put().
  */
-void drm_mode_object_reference(struct drm_mode_object *obj)
+void drm_mode_object_get(struct drm_mode_object *obj)
 {
 	if (obj->free_cb) {
 		DRM_DEBUG("OBJ ID: %d (%d)\n", obj->id, atomic_read(&obj->refcount.refcount));
 		kref_get(&obj->refcount);
 	}
 }
-EXPORT_SYMBOL(drm_mode_object_reference);
+EXPORT_SYMBOL(drm_mode_object_get);
 
 /**
  * drm_object_attach_property - attach a property to a modeset object
···
 			&arg->count_props);
 
 out_unref:
-	drm_mode_object_unreference(obj);
+	drm_mode_object_put(obj);
 out:
 	drm_modeset_unlock_all(dev);
 	return ret;
···
 	drm_property_change_valid_put(property, ref);
 
 out_unref:
-	drm_mode_object_unreference(arg_obj);
+	drm_mode_object_put(arg_obj);
 out:
 	drm_modeset_unlock_all(dev);
 	return ret;

drivers/gpu/drm/drm_property.c

···
 	if (!blob)
 		return;
 
-	drm_mode_object_unreference(&blob->base);
+	drm_mode_object_put(&blob->base);
 }
 EXPORT_SYMBOL(drm_property_unreference_blob);
 
···
  */
 struct drm_property_blob *drm_property_reference_blob(struct drm_property_blob *blob)
 {
-	drm_mode_object_reference(&blob->base);
+	drm_mode_object_get(&blob->base);
 	return blob;
 }
 EXPORT_SYMBOL(drm_property_reference_blob);
···
 		return;
 
 	if (drm_property_type_is(property, DRM_MODE_PROP_OBJECT)) {
-		drm_mode_object_unreference(ref);
+		drm_mode_object_put(ref);
 	} else if (drm_property_type_is(property, DRM_MODE_PROP_BLOB))
 		drm_property_unreference_blob(obj_to_blob(ref));
 }

include/drm/drm_mode_object.h

···
  *   drm_object_attach_property() before the object is visible to userspace.
  *
  * - For objects with dynamic lifetimes (as indicated by a non-NULL @free_cb) it
- *   provides reference counting through drm_mode_object_reference() and
- *   drm_mode_object_unreference(). This is used by &drm_framebuffer,
- *   &drm_connector and &drm_property_blob. These objects provide specialized
- *   reference counting wrappers.
+ *   provides reference counting through drm_mode_object_get() and
+ *   drm_mode_object_put(). This is used by &drm_framebuffer, &drm_connector
+ *   and &drm_property_blob. These objects provide specialized reference
+ *   counting wrappers.
  */
 struct drm_mode_object {
 	uint32_t id;
···
 
 struct drm_mode_object *drm_mode_object_find(struct drm_device *dev,
 					     uint32_t id, uint32_t type);
-void drm_mode_object_reference(struct drm_mode_object *obj);
-void drm_mode_object_unreference(struct drm_mode_object *obj);
+void drm_mode_object_get(struct drm_mode_object *obj);
+void drm_mode_object_put(struct drm_mode_object *obj);
+
+/**
+ * drm_mode_object_reference - acquire a mode object reference
+ * @obj: DRM mode object
+ *
+ * This is a compatibility alias for drm_mode_object_get() and should not be
+ * used by new code.
+ */
+static inline void drm_mode_object_reference(struct drm_mode_object *obj)
+{
+	drm_mode_object_get(obj);
+}
+
+/**
+ * drm_mode_object_unreference - release a mode object reference
+ * @obj: DRM mode object
+ *
+ * This is a compatibility alias for drm_mode_object_put() and should not be
+ * used by new code.
+ */
+static inline void drm_mode_object_unreference(struct drm_mode_object *obj)
+{
+	drm_mode_object_put(obj);
+}
 
 int drm_object_property_set_value(struct drm_mode_object *obj,
 				  struct drm_property *property,

scripts/coccinelle/api/drm-get-put.cocci

···
+///
+/// Use drm_*_get() and drm_*_put() helpers instead of drm_*_reference() and
+/// drm_*_unreference() helpers.
+///
+// Confidence: High
+// Copyright: (C) 2017 NVIDIA Corporation
+// Options: --no-includes --include-headers
+//
+
+virtual patch
+virtual report
+
+@depends on patch@
+expression object;
+@@
+
+(
+- drm_mode_object_reference(object)
++ drm_mode_object_get(object)
+|
+- drm_mode_object_unreference(object)
++ drm_mode_object_put(object)
+)
+
+@r depends on report@
+expression object;
+position p;
+@@
+
+(
+drm_mode_object_unreference@p(object)
+|
+drm_mode_object_reference@p(object)
+)
+
+@script:python depends on report@
+object << r.object;
+p << r.p;
+@@
+
+msg="WARNING: use get/put helpers to reference and dereference %s" % (object)
+coccilib.report.print_report(p[0], msg)