[PATCH v4 14/26] media: mc: Refcount the media device

[Sakari Ailus <sakari.ailus@linux.intel.com>]

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@linux.intel.com>
Acked-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
---
 drivers/media/mc/mc-device.c  | 35 +++++++++++++++++++++++++++++------
 drivers/media/mc/mc-devnode.c |  2 +-
 include/media/media-device.h  | 35 +++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/drivers/media/mc/mc-device.c b/drivers/media/mc/mc-device.c
index f1d89d940fe1..bbc233e726d2 100644
--- a/drivers/media/mc/mc-device.c
+++ b/drivers/media/mc/mc-device.c
@@ -700,6 +700,31 @@ 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);
+
+	if (mdev->ops && mdev->ops->release) {
+		/*
+		 * If release op isn't set, __media_device_release() is called
+		 * via media_device_cleanup().
+		 */
+		__media_device_release(mdev);
+		mdev->ops->release(mdev);
+	}
+}
+
 void media_device_init(struct media_device *mdev)
 {
 	INIT_LIST_HEAD(&mdev->entities);
@@ -713,6 +738,7 @@ void media_device_init(struct media_device *mdev)
 	ida_init(&mdev->entity_internal_idx);
 	atomic_set(&mdev->request_id, 0);
 
+	mdev->devnode.release = media_device_release;
 	media_devnode_init(&mdev->devnode);
 
 	if (!*mdev->bus_info)
@@ -725,12 +751,9 @@ 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);
+	WARN_ON(mdev->ops && mdev->ops->release);
+	__media_device_release(mdev);
+	media_device_put(mdev);
 }
 EXPORT_SYMBOL_GPL(media_device_cleanup);
 
diff --git a/drivers/media/mc/mc-devnode.c b/drivers/media/mc/mc-devnode.c
index 214b9b142d90..f27d5d288a38 100644
--- a/drivers/media/mc/mc-devnode.c
+++ b/drivers/media/mc/mc-devnode.c
@@ -200,6 +200,7 @@ static const struct file_operations media_devnode_fops = {
 void media_devnode_init(struct media_devnode *devnode)
 {
 	device_initialize(&devnode->dev);
+	devnode->dev.release = media_devnode_release;
 }
 
 int __must_check media_devnode_register(struct media_devnode *devnode,
@@ -229,7 +230,6 @@ int __must_check media_devnode_register(struct media_devnode *devnode,
 
 	devnode->dev.bus = &media_bus_type;
 	devnode->dev.devt = MKDEV(MAJOR(media_dev_t), devnode->minor);
-	devnode->dev.release = media_devnode_release;
 	if (devnode->parent)
 		devnode->dev.parent = devnode->parent;
 	dev_set_name(&devnode->dev, "media%d", devnode->minor);
diff --git a/include/media/media-device.h b/include/media/media-device.h
index c791f3d5ad77..f1afbfc4dca2 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 +221,32 @@ struct usb_device;
  */
 void media_device_init(struct media_device *mdev);
 
+/**
+ * media_device_get() - atomically increment the reference count for the media
+ * device
+ *
+ * Returns: the media device
+ *
+ * @mdev: media device
+ */
+static inline struct media_device *media_device_get(struct media_device *mdev)
+{
+	get_device(&mdev->devnode.dev);
+
+	return mdev;
+}
+
+/**
+ * media_device_put() - atomically decrement the reference count for the media
+ * device
+ *
+ * @mdev: media device
+ */
+static inline void media_device_put(struct media_device *mdev)
+{
+	put_device(&mdev->devnode.dev);
+}
+
 /**
  * media_device_cleanup() - Cleanups a media device element
  *
@@ -435,6 +463,13 @@ void __media_device_usb_init(struct media_device *mdev,
 static inline void media_device_init(struct media_device *mdev)
 {
 }
+static inline struct media_device *media_device_get(struct media_device *mdev)
+{
+	return NULL;
+}
+static inline void media_device_put(struct media_device *mdev)
+{
+}
 static inline int media_device_register(struct media_device *mdev)
 {
 	return 0;
-- 
2.39.2