[09/10,RFC] v4l2-device: add kref and a release function

Commit Message

Hans Verkuil Dec. 29, 2010, 9:43 p.m. UTC

None

Patch

diff --git a/drivers/media/video/v4l2-dev.c b/drivers/media/video/v4l2-dev.c
index 96ec954..c83d8a9 100644
--- a/drivers/media/video/v4l2-dev.c
+++ b/drivers/media/video/v4l2-dev.c
@@ -143,6 +143,7 @@  static inline void video_put(struct video_device *vdev)
 static void v4l2_device_release(struct device *cd)
 {
 	struct video_device *vdev = to_video_device(cd);
+	struct v4l2_device *v4l2_dev = vdev->v4l2_dev;
 
 	mutex_lock(&videodev_lock);
 	if (video_device[vdev->minor] != vdev) {
@@ -169,6 +170,10 @@  static void v4l2_device_release(struct device *cd)
 	/* Release video_device and perform other
 	   cleanups as needed. */
 	vdev->release(vdev);
+
+	/* Decrease v4l2_device refcount */
+	if (v4l2_dev)
+		v4l2_device_put(v4l2_dev);
 }
 
 static struct class video_class = {
@@ -670,6 +675,9 @@  static int __video_register_device(struct video_device *vdev, int type, int nr,
 		printk(KERN_WARNING "%s: requested %s%d, got %s\n", __func__,
 			name_base, nr, video_device_node_name(vdev));
 
+	/* Increase v4l2_device refcount */
+	if (vdev->v4l2_dev)
+		v4l2_device_get(vdev->v4l2_dev);
 	/* Part 5: Activate this minor. The char device can now be used. */
 	set_bit(V4L2_FL_REGISTERED, &vdev->flags);
 	mutex_lock(&videodev_lock);
diff --git a/drivers/media/video/v4l2-device.c b/drivers/media/video/v4l2-device.c
index e12844c..4124016 100644
--- a/drivers/media/video/v4l2-device.c
+++ b/drivers/media/video/v4l2-device.c
@@ -55,6 +55,21 @@  int v4l2_device_register(struct device *dev, struct v4l2_device *v4l2_dev)
 }
 EXPORT_SYMBOL_GPL(v4l2_device_register);
 
+static void v4l2_device_release(struct kref *ref)
+{
+	struct v4l2_device *v4l2_dev =
+		container_of(ref, struct v4l2_device, ref);
+
+	if (v4l2_dev->release)
+		v4l2_dev->release(v4l2_dev);
+}
+
+int v4l2_device_put(struct v4l2_device *v4l2_dev)
+{
+	return kref_put(&v4l2_dev->ref, v4l2_device_release);
+}
+EXPORT_SYMBOL_GPL(v4l2_device_put);
+
 int v4l2_device_set_name(struct v4l2_device *v4l2_dev, const char *basename,
 						atomic_t *instance)
 {
diff --git a/include/media/v4l2-device.h b/include/media/v4l2-device.h
index fd5d450..44763bc 100644
--- a/include/media/v4l2-device.h
+++ b/include/media/v4l2-device.h
@@ -56,8 +56,19 @@  struct v4l2_device {
 	struct v4l2_prio_state prio;
 	/* BKL replacement mutex. Temporary solution only. */
 	struct mutex ioctl_lock;
+	/* Keep track of the references to this struct. */
+	struct kref ref;
+	/* Release function that is called when the ref count goes to 0. */
+	void (*release)(struct v4l2_device *v4l2_dev);
 };
 
+static inline void v4l2_device_get(struct v4l2_device *v4l2_dev)
+{
+	kref_get(&v4l2_dev->ref);
+}
+
+int v4l2_device_put(struct v4l2_device *v4l2_dev);
+
 /* Initialize v4l2_dev and make dev->driver_data point to v4l2_dev.
    dev may be NULL in rare cases (ISA devices). In that case you
    must fill in the v4l2_dev->name field before calling this function. */