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, 5 insertions, 5 deletions

diff --git a/drivers/media/platform/xilinx/xilinx-dma.c b/drivers/media/platform/xilinx/xilinx-dma.c
index 18bfa6001909..fcfe0883aba5 100644
--- a/drivers/media/platform/xilinx/xilinx-dma.c
+++ b/drivers/media/platform/xilinx/xilinx-dma.c
@@ -469,7 +469,7 @@ static const struct vb2_ops xvip_dma_queue_qops = {
 static int
 xvip_dma_querycap(struct file *file, void *fh, struct v4l2_capability *cap)
 {
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct xvip_dma *dma = to_xvip_dma(vfh->vdev);
 
 	cap->capabilities = dma->xdev->v4l2_caps | V4L2_CAP_STREAMING |
@@ -491,7 +491,7 @@ xvip_dma_querycap(struct file *file, void *fh, struct v4l2_capability *cap)
 static int
 xvip_dma_enum_format(struct file *file, void *fh, struct v4l2_fmtdesc *f)
 {
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct xvip_dma *dma = to_xvip_dma(vfh->vdev);
 
 	if (f->index > 0)
@@ -505,7 +505,7 @@ xvip_dma_enum_format(struct file *file, void *fh, struct v4l2_fmtdesc *f)
 static int
 xvip_dma_get_format(struct file *file, void *fh, struct v4l2_format *format)
 {
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct xvip_dma *dma = to_xvip_dma(vfh->vdev);
 
 	format->fmt.pix = dma->format;
@@ -565,7 +565,7 @@ __xvip_dma_try_format(struct xvip_dma *dma, struct v4l2_pix_format *pix,
 static int
 xvip_dma_try_format(struct file *file, void *fh, struct v4l2_format *format)
 {
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct xvip_dma *dma = to_xvip_dma(vfh->vdev);
 
 	__xvip_dma_try_format(dma, &format->fmt.pix, NULL);
@@ -575,7 +575,7 @@ xvip_dma_try_format(struct file *file, void *fh, struct v4l2_format *format)
 static int
 xvip_dma_set_format(struct file *file, void *fh, struct v4l2_format *format)
 {
-	struct v4l2_fh *vfh = file->private_data;
+	struct v4l2_fh *vfh = file_to_v4l2_fh(file);
 	struct xvip_dma *dma = to_xvip_dma(vfh->vdev);
 	const struct xvip_video_format *info;