[PATCH 14/26] media device: Refcount the media device

[Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>]

As the struct media_device embeds struct media_devnode, the lifetime of
that object must be that same than that of the media_device.

References are obtained by media_device_get() and released by
media_device_put(). In order to use refcounting, the driver must set the
release callback before calling media_device_init() on the media device.

Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
---
 drivers/media/mc/mc-device.c | 43 +++++++++++++++++++++++++++++++-----
 include/media/media-device.h | 28 +++++++++++++++++++++++
 2 files changed, 65 insertions(+), 6 deletions(-)

diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
index f4d880fcd977..c13cbdfdbaab 100644
--- a/drivers/media/mc/mc-device.c
+++ b/drivers/media/mc/mc-device.c
@@ -705,6 +705,30 @@ void media_device_unregister_entity_notify(struct media_device *mdev,
 }
 EXPORT_SYMBOL_GPL(media_device_unregister_entity_notify);
 
+static void __media_device_release(struct media_device *mdev)
+{
+	dev_dbg(mdev->dev, "Media device released\n");
+
+	ida_destroy(&mdev->entity_internal_idx);
+	mdev->entity_internal_idx_max = 0;
+	media_graph_walk_cleanup(&mdev->pm_count_walk);
+	mutex_destroy(&mdev->graph_mutex);
+	mutex_destroy(&mdev->req_queue_mutex);
+}
+
+static void media_device_release(struct media_devnode *devnode)
+{
+	struct media_device *mdev = to_media_device(devnode);
+
+	__media_device_release(mdev);
+
+	if (mdev->ops && mdev->ops->release)
+		mdev->ops->release(mdev);
+	else
+		dev_warn(mdev->dev,
+			 "calling media_device_release but no release callback set!\n");
+}
+
 void media_device_init(struct media_device *mdev)
 {
 	INIT_LIST_HEAD(&mdev->entities);
@@ -717,6 +741,17 @@ void media_device_init(struct media_device *mdev)
 	mutex_init(&mdev->graph_mutex);
 	ida_init(&mdev->entity_internal_idx);
 	atomic_set(&mdev->request_id, 0);
+
+	/*
+	 * Set the release callback to the media device if we have one
+	 * set. Otherwise, the caller is responsible for calling
+	 * media_device_cleanup() in order to release resources
+	 * related to the media device, i.e. the media device is not
+	 * refcounted. This is deprecated.
+	 */
+	if (mdev->ops && mdev->ops->release)
+		mdev->devnode.release = media_device_release;
+
 	media_devnode_init(&mdev->devnode);
 
 	if (!*mdev->bus_info)
@@ -729,12 +764,8 @@ EXPORT_SYMBOL_GPL(media_device_init);
 
 void media_device_cleanup(struct media_device *mdev)
 {
-	ida_destroy(&mdev->entity_internal_idx);
-	mdev->entity_internal_idx_max = 0;
-	media_graph_walk_cleanup(&mdev->pm_count_walk);
-	mutex_destroy(&mdev->graph_mutex);
-	mutex_destroy(&mdev->req_queue_mutex);
-	put_device(&mdev->devnode.dev);
+	__media_device_release(mdev);
+	media_device_put(mdev);
 }
 EXPORT_SYMBOL_GPL(media_device_cleanup);
 
diff --git a/include/media/media-device.h b/include/media/media-device.h
index a33820075aa4..7e8bca6756ba 100644
--- a/include/media/media-device.h
+++ b/include/media/media-device.h
@@ -62,6 +62,7 @@ struct media_entity_notify {
  *	       request (and thus the buffer) must be available to the driver.
  *	       And once a buffer is queued, then the driver can complete
  *	       or delete objects from the request before req_queue exits.
+ * @release: Release the resources of the media device.
  */
 struct media_device_ops {
 	int (*link_notify)(struct media_link *link, u32 flags,
@@ -70,6 +71,7 @@ struct media_device_ops {
 	void (*req_free)(struct media_request *req);
 	int (*req_validate)(struct media_request *req);
 	void (*req_queue)(struct media_request *req);
+	void (*release)(struct media_device *mdev);
 };
 
 /**
@@ -219,6 +221,30 @@ struct usb_device;
  */
 void media_device_init(struct media_device *mdev);
 
+/**
+ * media_device_get() - Get a reference to a media device
+ *
+ * @mdev: media device
+ */
+#define media_device_get(mdev)						\
+	do {								\
+		dev_dbg((mdev)->dev, "%s: get media device %s\n",	\
+			__func__, (mdev)->bus_info);			\
+		get_device(&(mdev)->devnode.dev);			\
+	} while (0)
+
+/**
+ * media_device_put() - Put a reference to a media device
+ *
+ * @mdev: media device
+ */
+#define media_device_put(mdev)						\
+	do {								\
+		dev_dbg((mdev)->dev, "%s: put media device %s\n",	\
+			__func__, (mdev)->bus_info);			\
+		put_device(&(mdev)->devnode.dev);			\
+	} while (0)
+
 /**
  * media_device_cleanup() - Cleanups a media device element
  *
@@ -432,6 +458,8 @@ void __media_device_usb_init(struct media_device *mdev,
 			     const char *driver_name);
 
 #else
+#define media_device_get(mdev) do { } while (0)
+#define media_device_put(mdev) do { } while (0)
 static inline int media_device_register(struct media_device *mdev)
 {
 	return 0;
-- 
2.30.2