[PATCH 5.4 014/320] media: v4l2-ioctl.c: readbuffers depends on V4L2_CAP_READWRITE

Greg Kroah-Hartman
2022-01-24T19:52:06Z

From: Hans Verkuil <hverkuil-cisco@xs4all.nl>

commit cd9d9377ed235b294a492a094e1666178a5e78fd upstream.

If V4L2_CAP_READWRITE is not set, then readbuffers must be set to 0,
otherwise v4l2-compliance will complain.

A note on the Fixes tag below: this patch does not really fix that commit,
but it can be applied from that commit onwards. For older code there is no
guarantee that device_caps is set, so even though this patch would apply,
it will not work reliably.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Fixes: 049e684f2de9 (media: v4l2-dev: fix WARN_ON(!vdev->device_caps))
Cc: <stable@vger.kernel.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/media/v4l2-core/v4l2-ioctl.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/media/v4l2-core/v4l2-ioctl.c
+++ b/drivers/media/v4l2-core/v4l2-ioctl.c
@@ -2046,6 +2046,7 @@ static int v4l_prepare_buf(const struct
static int v4l_g_parm(const struct v4l2_ioctl_ops *ops,
struct file *file, void *fh, void *arg)
{
+ struct video_device *vfd = video_devdata(file);
struct v4l2_streamparm *p = arg;
v4l2_std_id std;
int ret = check_fmt(file, p->type);
@@ -2057,7 +2058,8 @@ static int v4l_g_parm(const struct v4l2_
if (p->type != V4L2_BUF_TYPE_VIDEO_CAPTURE &&
p->type != V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE)
return -EINVAL;
- p->parm.capture.readbuffers = 2;
+ if (vfd->device_caps & V4L2_CAP_READWRITE)
+ p->parm.capture.readbuffers = 2;
ret = ops->vidioc_g_std(file, fh, &std);
if (ret == 0)
v4l2_video_std_frame_period(std, &p->parm.capture.timeperframe);