media: Wrap file->private_data access with a helper function

Accessing file->private_data manually to retrieve the v4l2_fh pointer is
error-prone, as the field is a void * and will happily convert
implicitly to any pointer type. To avoid direct access to
file->private_data, introduce a new inline function that retrieves the
v4l2_fh pointer, and use it to replace common access patterns through
the kernel.

Changes to drivers have been generated with the following coccinelle
semantic patch:

@@
struct file *filp;
identifier fh;
@@

-       struct v4l2_fh *fh = filp->private_data;
+       struct v4l2_fh *fh = file_to_v4l2_fh(filp);

Manual changes have been applied to Documentation/ to update the usage
patterns, and to include/media/v4l2-fh.h to add the new function.

While at it, fix a typo in the title of v4l2-fh.rst: the file describes
the "file handles" API, not "file handlers".

No functional change is intended, this only paves the way to remove
direct accesses to file->private_data and make V4L2 drivers safer.
Other accesses to the field will be addressed separately.

Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

1 files changed, 4 insertions, 4 deletions

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 4fd25fea3b58..29d3b788b288 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -122,7 +122,7 @@ static int subdev_close(struct file *file)
 {
 	struct video_device *vdev = video_devdata(file);
 	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
 
 	if (sd->internal_ops && sd->internal_ops->close)
@@ -612,7 +612,7 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
 {
 	struct video_device *vdev = video_devdata(file);
 	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
 	bool ro_subdev = test_bit(V4L2_FL_SUBDEV_RO_DEVNODE, &vdev->flags);
 	bool streams_subdev = sd->flags & V4L2_SUBDEV_FL_STREAMS;
@@ -1135,7 +1135,7 @@ static long subdev_do_ioctl_lock(struct file *file, unsigned int cmd, void *arg)
 
 	if (video_is_registered(vdev)) {
 		struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
-		struct v4l2_fh *vfh = file->private_data;
+		struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 		struct v4l2_subdev_fh *subdev_fh = to_v4l2_subdev_fh(vfh);
 		struct v4l2_subdev_state *state;
 
@@ -1192,7 +1192,7 @@ static __poll_t subdev_poll(struct file *file, poll_table *wait)
 {
 	struct video_device *vdev = video_devdata(file);
 	struct v4l2_subdev *sd = vdev_to_v4l2_subdev(vdev);
-	struct v4l2_fh *fh = file->private_data;
+	struct v4l2_fh *fh = file_to_v4l2_fh(file);
 
 	if (!(sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS))
 		return EPOLLERR;