Document the interface for metadata output, including
V4L2_BUF_TYPE_META_OUTPUT buffer type and V4L2_CAP_META_OUTPUT capability
bits.
Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
Acked-by: Hans Verkuil <hans.verkuil@xxxxxxxxx>
Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
Tested-by: Tian Shu Qiu <tian.shu.qiu@xxxxxxxxx>
---
Documentation/media/uapi/v4l/buffer.rst | 3 +++
Documentation/media/uapi/v4l/dev-meta.rst | 33 ++++++++++++++----------
Documentation/media/uapi/v4l/vidioc-querycap.rst | 3 +++
Documentation/media/videodev2.h.rst.exceptions | 2 ++
4 files changed, 28 insertions(+), 13 deletions(-)
diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst
index c5013adaa44d9..86878bb0087f2 100644
--- a/Documentation/media/uapi/v4l/buffer.rst
+++ b/Documentation/media/uapi/v4l/buffer.rst
@@ -472,6 +472,9 @@ enum v4l2_buf_type
* - ``V4L2_BUF_TYPE_META_CAPTURE``
- 13
- Buffer for metadata capture, see :ref:`metadata`.
+ * - ``V4L2_BUF_TYPE_META_OUTPUT``
+ - 14
+ - Buffer for metadata output, see :ref:`metadata`.
diff --git a/Documentation/media/uapi/v4l/dev-meta.rst b/Documentation/media/uapi/v4l/dev-meta.rst
index edccb9bd8858c..c5dbe882be654 100644
--- a/Documentation/media/uapi/v4l/dev-meta.rst
+++ b/Documentation/media/uapi/v4l/dev-meta.rst
@@ -14,21 +14,27 @@ Metadata Interface
******************
Metadata refers to any non-image data that supplements video frames with
-additional information. This may include statistics computed over the image
-or frame capture parameters supplied by the image source. This interface is
-intended for transfer of metadata to userspace and control of that operation.
+additional information. This may include statistics computed over the image,
+frame capture parameters supplied by the image source or device specific
+parameters for specifying how the device processes images. This interface is
+intended for transfer of metadata between the userspace and the hardware and
+control of that operation.
-The metadata interface is implemented on video capture device nodes. The device
-can be dedicated to metadata or can implement both video and metadata capture
-as specified in its reported capabilities.
+The metadata interface is implemented on video device nodes. The device can be
+dedicated to metadata or can support both video and metadata as specified in its
+reported capabilities.
Querying Capabilities
=====================
-Device nodes supporting the metadata interface set the ``V4L2_CAP_META_CAPTURE``
-flag in the ``device_caps`` field of the
+Device nodes supporting the metadata capture interface set the
+``V4L2_CAP_META_CAPTURE`` flag in the ``device_caps`` field of the
:c:type:`v4l2_capability` structure returned by the :c:func:`VIDIOC_QUERYCAP`
-ioctl. That flag means the device can capture metadata to memory.
+ioctl. That flag means the device can capture metadata to memory. Similarly,
+device nodes supporting metadata output interface set the
+``V4L2_CAP_META_OUTPUT`` flag in the ``device_caps`` field of
+:c:type:`v4l2_capability` structure. That flag means the device can read
+metadata from memory.
At least one of the read/write or streaming I/O methods must be supported.
@@ -42,10 +48,11 @@ to the basic :ref:`format` ioctls, the :c:func:`VIDIOC_ENUM_FMT` ioctl must be
supported as well.
To use the :ref:`format` ioctls applications set the ``type`` field of the
-:c:type:`v4l2_format` structure to ``V4L2_BUF_TYPE_META_CAPTURE`` and use the
-:c:type:`v4l2_meta_format` ``meta`` member of the ``fmt`` union as needed per
-the desired operation. Both drivers and applications must set the remainder of
-the :c:type:`v4l2_format` structure to 0.
+:c:type:`v4l2_format` structure to ``V4L2_BUF_TYPE_META_CAPTURE`` or to
+``V4L2_BUF_TYPE_META_OUTPUT`` and use the :c:type:`v4l2_meta_format` ``meta``
+member of the ``fmt`` union as needed per the desired operation. Both drivers
+and applications must set the remainder of the :c:type:`v4l2_format` structure
+to 0.
.. c:type:: v4l2_meta_format
diff --git a/Documentation/media/uapi/v4l/vidioc-querycap.rst b/Documentation/media/uapi/v4l/vidioc-querycap.rst
index 0c7bc9568453f..5f9930195d624 100644
--- a/Documentation/media/uapi/v4l/vidioc-querycap.rst
+++ b/Documentation/media/uapi/v4l/vidioc-querycap.rst
@@ -258,6 +258,9 @@ specification the ioctl returns an ``EINVAL`` error code.
* - ``V4L2_CAP_STREAMING``
- 0x04000000
- The device supports the :ref:`streaming <mmap>` I/O method.
+ * - ``V4L2_CAP_META_OUTPUT``
+ - 0x08000000
+ - The device supports the :ref:`metadata` output interface.
* - ``V4L2_CAP_TOUCH``
- 0x10000000
- This is a touch device.
diff --git a/Documentation/media/videodev2.h.rst.exceptions b/Documentation/media/videodev2.h.rst.exceptions
index 4c4bcba0f307d..64d348e67df99 100644
--- a/Documentation/media/videodev2.h.rst.exceptions
+++ b/Documentation/media/videodev2.h.rst.exceptions
@@ -30,6 +30,7 @@ replace symbol V4L2_FIELD_TOP :c:type:`v4l2_field`
# Documented enum v4l2_buf_type
replace symbol V4L2_BUF_TYPE_META_CAPTURE :c:type:`v4l2_buf_type`
+replace symbol V4L2_BUF_TYPE_META_OUTPUT :c:type:`v4l2_buf_type`
replace symbol V4L2_BUF_TYPE_SDR_CAPTURE :c:type:`v4l2_buf_type`
replace symbol V4L2_BUF_TYPE_SDR_OUTPUT :c:type:`v4l2_buf_type`
replace symbol V4L2_BUF_TYPE_SLICED_VBI_CAPTURE :c:type:`v4l2_buf_type`
@@ -163,6 +164,7 @@ replace define V4L2_CAP_META_CAPTURE device-capabilities
replace define V4L2_CAP_READWRITE device-capabilities
replace define V4L2_CAP_ASYNCIO device-capabilities
replace define V4L2_CAP_STREAMING device-capabilities
+replace define V4L2_CAP_META_OUTPUT device-capabilities
replace define V4L2_CAP_DEVICE_CAPS device-capabilities
replace define V4L2_CAP_TOUCH device-capabilities
--
2.11.0
