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/platform/nxp/imx-jpeg/mxc-jpeg.c b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
index 8681dd193033..1b2148578cb6 100644
--- a/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
+++ b/drivers/media/platform/nxp/imx-jpeg/mxc-jpeg.c
@@ -1604,7 +1604,7 @@ end:
 static int mxc_jpeg_decoder_cmd(struct file *file, void *priv,
 				struct v4l2_decoder_cmd *cmd)
 {
-	struct v4l2_fh *fh = file->private_data;
+	struct v4l2_fh *fh = file_to_v4l2_fh(file);
 	struct mxc_jpeg_ctx *ctx = mxc_jpeg_fh_to_ctx(fh);
 	unsigned long flags;
 	int ret;
@@ -1637,7 +1637,7 @@ static int mxc_jpeg_decoder_cmd(struct file *file, void *priv,
 static int mxc_jpeg_encoder_cmd(struct file *file, void *priv,
 				struct v4l2_encoder_cmd *cmd)
 {
-	struct v4l2_fh *fh = file->private_data;
+	struct v4l2_fh *fh = file_to_v4l2_fh(file);
 	struct mxc_jpeg_ctx *ctx = mxc_jpeg_fh_to_ctx(fh);
 	unsigned long flags;
 	int ret;