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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Subject: [PATCH 5.15 042/846] media: v4l2-ioctl.c: readbuffers depends on V4L2_CAP_READWRITE
Date:   Mon, 24 Jan 2022 19:32:39 +0100
Message-Id: <20220124184102.400071146@linuxfoundation.org>
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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
@@ -2088,6 +2088,7 @@ 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);
@@ -2099,7 +2100,8 @@ 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);