drm: allocate minors early

Instead of waiting for device-registration, we now allocate minor-objects
during device allocation. The minors are not registered or assigned an ID.
This is still postponed to device-registration.

While at it, remove the superfluous output-parameter in drm_get_minor().

The reason for this early allocation is to make
dev->primary/control/render available atomically. So once the device is
alive, all of them are already set and we never have the situation where
one of them is set after another (they're either NULL or set, but never
changed). This will eventually allow us to reduce minor-ID allocation to
one base-ID instead of a single ID for each.
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_stub.c

@@ -260,21 +260,49 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data,
 	return 0;
 }
 
+static struct drm_minor **drm_minor_get_slot(struct drm_device *dev,
+					     unsigned int type)
+{
+	switch (type) {
+	case DRM_MINOR_LEGACY:
+		return &dev->primary;
+	case DRM_MINOR_RENDER:
+		return &dev->render;
+	case DRM_MINOR_CONTROL:
+		return &dev->control;
+	default:
+		return NULL;
+	}
+}
+
+static int drm_minor_alloc(struct drm_device *dev, unsigned int type)
+{
+	struct drm_minor *minor;
+
+	minor = kzalloc(sizeof(*minor), GFP_KERNEL);
+	if (!minor)
+		return -ENOMEM;
+
+	minor->type = type;
+	minor->dev = dev;
+	INIT_LIST_HEAD(&minor->master_list);
+
+	*drm_minor_get_slot(dev, type) = minor;
+	return 0;
+}
+
 /**
- * drm_get_minor - Allocate and register new DRM minor
+ * drm_get_minor - Register DRM minor
  * @dev: DRM device
- * @minor: Pointer to where new minor is stored
  * @type: Type of minor
  *
- * Allocate a new minor of the given type and register it. A pointer to the new
- * minor is returned in @minor.
+ * Register minor of given type.
  * Caller must hold the global DRM mutex.
  *
  * RETURNS:
  * 0 on success, negative error code on failure.
  */
-static int drm_get_minor(struct drm_device *dev, struct drm_minor **minor,
-			 int type)
+static int drm_get_minor(struct drm_device *dev, unsigned int type)
 {
 	struct drm_minor *new_minor;
 	int ret;
@@ -282,21 +310,16 @@ static int drm_get_minor(struct drm_device *dev, struct drm_minor **minor,
 
 	DRM_DEBUG("\n");
 
+	new_minor = *drm_minor_get_slot(dev, type);
+	if (!new_minor)
+		return 0;
+
 	minor_id = drm_minor_get_id(dev, type);
 	if (minor_id < 0)
 		return minor_id;
 
-	new_minor = kzalloc(sizeof(struct drm_minor), GFP_KERNEL);
-	if (!new_minor) {
-		ret = -ENOMEM;
-		goto err_idr;
-	}
-
-	new_minor->type = type;
 	new_minor->device = MKDEV(DRM_MAJOR, minor_id);
-	new_minor->dev = dev;
 	new_minor->index = minor_id;
-	INIT_LIST_HEAD(&new_minor->master_list);
 
 	idr_replace(&drm_minors_idr, new_minor, minor_id);
 
@@ -314,7 +337,6 @@ static int drm_get_minor(struct drm_device *dev, struct drm_minor **minor,
 		       "DRM: Error sysfs_device_add.\n");
 		goto err_debugfs;
 	}
-	*minor = new_minor;
 
 	DRM_DEBUG("new minor assigned %d\n", minor_id);
 	return 0;
@@ -325,10 +347,7 @@ static int drm_get_minor(struct drm_device *dev, struct drm_minor **minor,
 	drm_debugfs_cleanup(new_minor);
 err_mem:
 #endif
-	kfree(new_minor);
-err_idr:
 	idr_remove(&drm_minors_idr, minor_id);
-	*minor = NULL;
 	return ret;
 }
 
@@ -495,8 +514,24 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver,
 	mutex_init(&dev->struct_mutex);
 	mutex_init(&dev->ctxlist_mutex);
 
+	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
+		ret = drm_minor_alloc(dev, DRM_MINOR_CONTROL);
+		if (ret)
+			goto err_minors;
+	}
+
+	if (drm_core_check_feature(dev, DRIVER_RENDER) && drm_rnodes) {
+		ret = drm_minor_alloc(dev, DRM_MINOR_RENDER);
+		if (ret)
+			goto err_minors;
+	}
+
+	ret = drm_minor_alloc(dev, DRM_MINOR_LEGACY);
+	if (ret)
+		goto err_minors;
+
 	if (drm_ht_create(&dev->map_hash, 12))
-		goto err_free;
+		goto err_minors;
 
 	ret = drm_ctxbitmap_init(dev);
 	if (ret) {
@@ -518,7 +553,10 @@ struct drm_device *drm_dev_alloc(struct drm_driver *driver,
 	drm_ctxbitmap_cleanup(dev);
 err_ht:
 	drm_ht_remove(&dev->map_hash);
-err_free:
+err_minors:
+	drm_put_minor(dev->control);
+	drm_put_minor(dev->render);
+	drm_put_minor(dev->primary);
 	kfree(dev);
 	return NULL;
 }
@@ -594,26 +632,22 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 
 	mutex_lock(&drm_global_mutex);
 
-	if (drm_core_check_feature(dev, DRIVER_MODESET)) {
-		ret = drm_get_minor(dev, &dev->control, DRM_MINOR_CONTROL);
-		if (ret)
-			goto out_unlock;
-	}
+	ret = drm_get_minor(dev, DRM_MINOR_CONTROL);
+	if (ret)
+		goto err_minors;
 
-	if (drm_core_check_feature(dev, DRIVER_RENDER) && drm_rnodes) {
-		ret = drm_get_minor(dev, &dev->render, DRM_MINOR_RENDER);
-		if (ret)
-			goto err_control_node;
-	}
+	ret = drm_get_minor(dev, DRM_MINOR_RENDER);
+	if (ret)
+		goto err_minors;
 
-	ret = drm_get_minor(dev, &dev->primary, DRM_MINOR_LEGACY);
+	ret = drm_get_minor(dev, DRM_MINOR_LEGACY);
 	if (ret)
-		goto err_render_node;
+		goto err_minors;
 
 	if (dev->driver->load) {
 		ret = dev->driver->load(dev, flags);
 		if (ret)
-			goto err_primary_node;
+			goto err_minors;
 	}
 
 	/* setup grouping for legacy outputs */
@@ -630,12 +664,10 @@ int drm_dev_register(struct drm_device *dev, unsigned long flags)
 err_unload:
 	if (dev->driver->unload)
 		dev->driver->unload(dev);
-err_primary_node:
-	drm_unplug_minor(dev->primary);
-err_render_node:
-	drm_unplug_minor(dev->render);
-err_control_node:
+err_minors:
 	drm_unplug_minor(dev->control);
+	drm_unplug_minor(dev->render);
+	drm_unplug_minor(dev->primary);
 out_unlock:
 	mutex_unlock(&drm_global_mutex);
 	return ret;