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, 1 insertions, 1 deletions

diff --git a/drivers/media/platform/allegro-dvt/allegro-core.c b/drivers/media/platform/allegro-dvt/allegro-core.c
index eb03df0d8652..1f134e08923a 100644
--- a/drivers/media/platform/allegro-dvt/allegro-core.c
+++ b/drivers/media/platform/allegro-dvt/allegro-core.c
@@ -3483,7 +3483,7 @@ static int allegro_enum_framesizes(struct file *file, void *fh,
 static int allegro_ioctl_streamon(struct file *file, void *priv,
 				  enum v4l2_buf_type type)
 {
-	struct v4l2_fh *fh = file->private_data;
+	struct v4l2_fh *fh = file_to_v4l2_fh(file);
 	struct allegro_channel *channel = fh_to_channel(fh);
 	int err;