[media] v4l: add buffer exporting via dmabuf

This patch adds extension to V4L2 api. A new ioctl VIDIOC_EXPBUF is added.  The
ioctl is used to export an mmap buffer as a DMABUF file descriptor.

Signed-off-by: Tomasz Stanislawski <t.stanislaws@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/v4l2-core/v4l2-compat-ioctl32.c

@@ -1018,6 +1018,7 @@ long v4l2_compat_ioctl32(struct file *file, unsigned int cmd, unsigned long arg)
 	case VIDIOC_S_FBUF32:
 	case VIDIOC_OVERLAY32:
 	case VIDIOC_QBUF32:
+	case VIDIOC_EXPBUF:
 	case VIDIOC_DQBUF32:
 	case VIDIOC_STREAMON32:
 	case VIDIOC_STREAMOFF32:

drivers/media/v4l2-core/v4l2-dev.c

@@ -571,6 +571,7 @@ static void determine_valid_ioctls(struct video_device *vdev)
 	SET_VALID_IOCTL(ops, VIDIOC_REQBUFS, vidioc_reqbufs);
 	SET_VALID_IOCTL(ops, VIDIOC_QUERYBUF, vidioc_querybuf);
 	SET_VALID_IOCTL(ops, VIDIOC_QBUF, vidioc_qbuf);
+	SET_VALID_IOCTL(ops, VIDIOC_EXPBUF, vidioc_expbuf);
 	SET_VALID_IOCTL(ops, VIDIOC_DQBUF, vidioc_dqbuf);
 	SET_VALID_IOCTL(ops, VIDIOC_STREAMON, vidioc_streamon);
 	SET_VALID_IOCTL(ops, VIDIOC_STREAMOFF, vidioc_streamoff);

drivers/media/v4l2-core/v4l2-ioctl.c

@@ -454,6 +454,15 @@ static void v4l_print_buffer(const void *arg, bool write_only)
 			tc->type, tc->flags, tc->frames, *(__u32 *)tc->userbits);
 }
 
+static void v4l_print_exportbuffer(const void *arg, bool write_only)
+{
+	const struct v4l2_exportbuffer *p = arg;
+
+	pr_cont("fd=%d, type=%s, index=%u, plane=%u, flags=0x%08x\n",
+		p->fd, prt_names(p->type, v4l2_type_names),
+		p->index, p->plane, p->flags);
+}
+
 static void v4l_print_create_buffers(const void *arg, bool write_only)
 {
 	const struct v4l2_create_buffers *p = arg;
@@ -1961,6 +1970,7 @@ static struct v4l2_ioctl_info v4l2_ioctls[] = {
 	IOCTL_INFO_STD(VIDIOC_S_FBUF, vidioc_s_fbuf, v4l_print_framebuffer, INFO_FL_PRIO),
 	IOCTL_INFO_FNC(VIDIOC_OVERLAY, v4l_overlay, v4l_print_u32, INFO_FL_PRIO),
 	IOCTL_INFO_FNC(VIDIOC_QBUF, v4l_qbuf, v4l_print_buffer, INFO_FL_QUEUE),
+	IOCTL_INFO_STD(VIDIOC_EXPBUF, vidioc_expbuf, v4l_print_exportbuffer, INFO_FL_QUEUE | INFO_FL_CLEAR(v4l2_exportbuffer, flags)),
 	IOCTL_INFO_FNC(VIDIOC_DQBUF, v4l_dqbuf, v4l_print_buffer, INFO_FL_QUEUE),
 	IOCTL_INFO_FNC(VIDIOC_STREAMON, v4l_streamon, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),
 	IOCTL_INFO_FNC(VIDIOC_STREAMOFF, v4l_streamoff, v4l_print_buftype, INFO_FL_PRIO | INFO_FL_QUEUE),

include/media/v4l2-ioctl.h

@@ -111,6 +111,8 @@ struct v4l2_ioctl_ops {
 	int (*vidioc_reqbufs) (struct file *file, void *fh, struct v4l2_requestbuffers *b);
 	int (*vidioc_querybuf)(struct file *file, void *fh, struct v4l2_buffer *b);
 	int (*vidioc_qbuf)    (struct file *file, void *fh, struct v4l2_buffer *b);
+	int (*vidioc_expbuf)  (struct file *file, void *fh,
+				struct v4l2_exportbuffer *e);
 	int (*vidioc_dqbuf)   (struct file *file, void *fh, struct v4l2_buffer *b);
 
 	int (*vidioc_create_bufs)(struct file *file, void *fh, struct v4l2_create_buffers *b);

include/uapi/linux/videodev2.h

@@ -694,6 +694,33 @@ struct v4l2_buffer {
 #define V4L2_BUF_FLAG_NO_CACHE_INVALIDATE	0x0800
 #define V4L2_BUF_FLAG_NO_CACHE_CLEAN		0x1000
 
+/**
+ * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor
+ *
+ * @index:	id number of the buffer
+ * @type:	enum v4l2_buf_type; buffer type (type == *_MPLANE for
+ *		multiplanar buffers);
+ * @plane:	index of the plane to be exported, 0 for single plane queues
+ * @flags:	flags for newly created file, currently only O_CLOEXEC is
+ *		supported, refer to manual of open syscall for more details
+ * @fd:		file descriptor associated with DMABUF (set by driver)
+ *
+ * Contains data used for exporting a video buffer as DMABUF file descriptor.
+ * The buffer is identified by a 'cookie' returned by VIDIOC_QUERYBUF
+ * (identical to the cookie used to mmap() the buffer to userspace). All
+ * reserved fields must be set to zero. The field reserved0 is expected to
+ * become a structure 'type' allowing an alternative layout of the structure
+ * content. Therefore this field should not be used for any other extensions.
+ */
+struct v4l2_exportbuffer {
+	__u32		type; /* enum v4l2_buf_type */
+	__u32		index;
+	__u32		plane;
+	__u32		flags;
+	__s32		fd;
+	__u32		reserved[11];
+};
+
 /*
  *	O V E R L A Y   P R E V I E W
  */
@@ -1895,6 +1922,7 @@ struct v4l2_create_buffers {
 #define VIDIOC_S_FBUF		 _IOW('V', 11, struct v4l2_framebuffer)
 #define VIDIOC_OVERLAY		 _IOW('V', 14, int)
 #define VIDIOC_QBUF		_IOWR('V', 15, struct v4l2_buffer)
+#define VIDIOC_EXPBUF		_IOWR('V', 16, struct v4l2_exportbuffer)
 #define VIDIOC_DQBUF		_IOWR('V', 17, struct v4l2_buffer)
 #define VIDIOC_STREAMON		 _IOW('V', 18, int)
 #define VIDIOC_STREAMOFF	 _IOW('V', 19, int)