v4l2: V4L2CameraProxy: Add support for PREPARE_BUF as one of the supported ioctl

Add support for PREPARE_BUF as one of the ioctl. Since this is a compat
layer, there doesn't seem to be an equivalent to the "transfer ownership
of the buffer to kernel driver" in V4L2Camera class. Thus, simply
duplicate the checks done by vidioc_qbuf.

To match the error checks done by kernel implementation, we'd have to
check if dmabuf fd is valid and that the buffer size is large enough.
Doing so will not add any particular value to the program as
applications most likely don't depend on these conditions being
handled correctly.

Signed-off-by: Vedant Paranjape <vedantparanjape160201@gmail.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

2 files changed, 35 insertions, 1 deletions

diff --git a/src/v4l2/v4l2_camera_proxy.cpp b/src/v4l2/v4l2_camera_proxy.cpp
index ec6daac6..f3470a6d 100644
--- a/src/v4l2/v4l2_camera_proxy.cpp
+++ b/src/v4l2/v4l2_camera_proxy.cpp
@@ -559,6 +559,38 @@ int V4L2CameraProxy::vidioc_querybuf(V4L2CameraFile *file, struct v4l2_buffer *a
 	return 0;
 }
 
+int V4L2CameraProxy::vidioc_prepare_buf(V4L2CameraFile *file, struct v4l2_buffer *arg)
+{
+	LOG(V4L2Compat, Debug)
+		<< "[" << file->description() << "] " << __func__
+		<< "(index=" << arg->index << ")";
+
+	if (!hasOwnership(file))
+		return -EBUSY;
+
+	if (arg->index >= bufferCount_)
+		return -EINVAL;
+
+	if (arg->flags & V4L2_BUF_FLAG_REQUEST_FD)
+		return -EINVAL;
+
+	if (!validateBufferType(arg->type) ||
+	    !validateMemoryType(arg->memory))
+		return -EINVAL;
+
+	struct v4l2_buffer &buffer = buffers_[arg->index];
+
+	if (buffer.flags & V4L2_BUF_FLAG_QUEUED ||
+	    buffer.flags & V4L2_BUF_FLAG_PREPARED)
+		return -EINVAL;
+
+	buffer.flags |= V4L2_BUF_FLAG_PREPARED;
+
+	arg->flags = buffer.flags;
+
+	return 0;
+}
+
 int V4L2CameraProxy::vidioc_qbuf(V4L2CameraFile *file, struct v4l2_buffer *arg)
 {
 	LOG(V4L2Compat, Debug)
@@ -627,7 +659,7 @@ int V4L2CameraProxy::vidioc_dqbuf(V4L2CameraFile *file, struct v4l2_buffer *arg,
 
 	struct v4l2_buffer &buf = buffers_[currentBuf_];
 
-	buf.flags &= ~(V4L2_BUF_FLAG_QUEUED | V4L2_BUF_FLAG_DONE);
+	buf.flags &= ~(V4L2_BUF_FLAG_QUEUED | V4L2_BUF_FLAG_DONE | V4L2_BUF_FLAG_PREPARED);
 	buf.length = sizeimage_;
 	*arg = buf;
 
@@ -729,6 +761,7 @@ const std::set<unsigned long> V4L2CameraProxy::supportedIoctls_ = {
 	VIDIOC_S_INPUT,
 	VIDIOC_REQBUFS,
 	VIDIOC_QUERYBUF,
+	VIDIOC_PREPARE_BUF,
 	VIDIOC_QBUF,
 	VIDIOC_DQBUF,
 	VIDIOC_EXPBUF,
diff --git a/src/v4l2/v4l2_camera_proxy.h b/src/v4l2/v4l2_camera_proxy.h
index a38b28c7..76ca2d8a 100644
--- a/src/v4l2/v4l2_camera_proxy.h
+++ b/src/v4l2/v4l2_camera_proxy.h
@@ -58,6 +58,7 @@ private:
 	int vidioc_s_input(V4L2CameraFile *file, int *arg);
 	int vidioc_reqbufs(V4L2CameraFile *file, struct v4l2_requestbuffers *arg);
 	int vidioc_querybuf(V4L2CameraFile *file, struct v4l2_buffer *arg);
+	int vidioc_prepare_buf(V4L2CameraFile *file, struct v4l2_buffer *arg);
 	int vidioc_qbuf(V4L2CameraFile *file, struct v4l2_buffer *arg);
 	int vidioc_dqbuf(V4L2CameraFile *file, struct v4l2_buffer *arg,
 			 libcamera::Mutex *lock) LIBCAMERA_TSA_REQUIRES(*lock);