media: v4l2-subdev: handle module refcounting here

The module ownership refcounting was done in media_entity_get/put,
but that was very confusing and it did not work either in case an
application had a v4l-subdevX device open and the module was
unbound. When the v4l-subdevX device was closed the media_entity_put
was never called and the module refcount was left one too high, making
it impossible to unload it.

Since v4l2-subdev.c was the only place where media_entity_get/put was
called, just move the functionality to v4l2-subdev.c and drop those
confusing entity functions.

Store the module in subdev_fh so module_put no longer depends on
the media_entity struct.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

1 files changed, 9 insertions, 13 deletions

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index f5f0d71ec745..d75815ab0d7b 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -18,6 +18,7 @@
 
 #include <linux/ioctl.h>
 #include <linux/mm.h>
+#include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/videodev2.h>
@@ -54,9 +55,6 @@ static int subdev_open(struct file *file)
 	struct video_device *vdev = video_devdata(file);
 	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
 	struct v4l2_subdev_fh *subdev_fh;
-#if defined(CONFIG_MEDIA_CONTROLLER)
-	struct media_entity *entity = NULL;
-#endif
 	int ret;
 
 	subdev_fh = kzalloc(sizeof(*subdev_fh), GFP_KERNEL);
@@ -73,12 +71,15 @@ static int subdev_open(struct file *file)
 	v4l2_fh_add(&subdev_fh->vfh);
 	file->private_data = &subdev_fh->vfh;
 #if defined(CONFIG_MEDIA_CONTROLLER)
-	if (sd->v4l2_dev->mdev) {
-		entity = media_entity_get(&sd->entity);
-		if (!entity) {
+	if (sd->v4l2_dev->mdev && sd->entity.graph_obj.mdev->dev) {
+		struct module *owner;
+
+		owner = sd->entity.graph_obj.mdev->dev->driver->owner;
+		if (!try_module_get(owner)) {
 			ret = -EBUSY;
 			goto err;
 		}
+		subdev_fh->owner = owner;
 	}
 #endif
 
@@ -91,9 +92,7 @@ static int subdev_open(struct file *file)
 	return 0;
 
 err:
-#if defined(CONFIG_MEDIA_CONTROLLER)
-	media_entity_put(entity);
-#endif
+	module_put(subdev_fh->owner);
 	v4l2_fh_del(&subdev_fh->vfh);
 	v4l2_fh_exit(&subdev_fh->vfh);
 	subdev_fh_free(subdev_fh);
@@ -111,10 +110,7 @@ static int subdev_close(struct file *file)
 
 	if (sd->internal_ops && sd->internal_ops->close)
 		sd->internal_ops->close(sd, subdev_fh);
-#if defined(CONFIG_MEDIA_CONTROLLER)
-	if (sd->v4l2_dev->mdev)
-		media_entity_put(&sd->entity);
-#endif
+	module_put(subdev_fh->owner);
 	v4l2_fh_del(vfh);
 	v4l2_fh_exit(vfh);
 	subdev_fh_free(subdev_fh);