From: Hans Verkuil <hverkuil-cisco@xs4all.nl> stable inclusion from stable-v5.10.94 commit 7cac8a56242779d8438f10723601e721c46cf41e bugzilla: https://gitee.com/openeuler/kernel/issues/I531X9 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- 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> Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com> Acked-by: Xie XiuQi <xiexiuqi@huawei.com> --- drivers/media/v4l2-core/v4l2-ioctl.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c index 4ffa14e44efe..6d6d30dbbe68 100644 --- a/drivers/media/v4l2-core/v4l2-ioctl.c +++ b/drivers/media/v4l2-core/v4l2-ioctl.c @@ -2127,6 +2127,7 @@ static int v4l_prepare_buf(const struct v4l2_ioctl_ops *ops, 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); @@ -2138,7 +2139,8 @@ static int v4l_g_parm(const struct v4l2_ioctl_ops *ops, 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); -- 2.20.1