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, 2 insertions, 2 deletions

diff --git a/drivers/media/v4l2-core/v4l2-ctrls-api.c b/drivers/media/v4l2-core/v4l2-ctrls-api.c
index d49a68b36c28..d46b2c8f3d23 100644
--- a/drivers/media/v4l2-core/v4l2-ctrls-api.c
+++ b/drivers/media/v4l2-core/v4l2-ctrls-api.c
@@ -1253,7 +1253,7 @@ EXPORT_SYMBOL(v4l2_querymenu);
 int v4l2_ctrl_log_status(struct file *file, void *fh)
 {
 	struct video_device *vfd = video_devdata(file);
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 
 	if (test_bit(V4L2_FL_USES_V4L2_FH, &vfd->flags) && vfd->v4l2_dev)
 		v4l2_ctrl_handler_log_status(vfh->ctrl_handler,
@@ -1348,7 +1348,7 @@ EXPORT_SYMBOL(v4l2_ctrl_subdev_subscribe_event);
  */
 __poll_t v4l2_ctrl_poll(struct file *file, struct poll_table_struct *wait)
 {
-	struct v4l2_fh *fh = file->private_data;
+	struct v4l2_fh *fh = file_to_v4l2_fh(file);
 
 	poll_wait(file, &fh->wait, wait);
 	if (v4l2_event_pending(fh))