From: Hans Verkuil <hansverk@xxxxxxxxx>
VIDIOC_REQBUFS and VIDIOC_CREATE_BUFFERS will return capabilities
telling userspace what the given buffer type is capable of.
Signed-off-by: Hans Verkuil <hansverk@xxxxxxxxx>
Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx>
---
.../media/uapi/v4l/vidioc-create-bufs.rst | 14 ++++++-
.../media/uapi/v4l/vidioc-reqbufs.rst | 42 ++++++++++++++++++-
include/uapi/linux/videodev2.h | 13 +++++-
3 files changed, 65 insertions(+), 4 deletions(-)
diff --git a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
index a39e18d69511..eadf6f757fbf 100644
--- a/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-create-bufs.rst
@@ -102,7 +102,19 @@ than the number requested.
- ``format``
- Filled in by the application, preserved by the driver.
* - __u32
- - ``reserved``\ [8]
+ - ``capabilities``
+ - Set by the driver. If 0, then the driver doesn't support
+ capabilities. In that case all you know is that the driver is
+ guaranteed to support ``V4L2_MEMORY_MMAP`` and *might* support
+ other :c:type:`v4l2_memory` types. It will not support any others
+ capabilities. See :ref:`here <v4l2-buf-capabilities>` for a list of the
+ capabilities.
+
+ If you want to just query the capabilities without making any
+ other changes, then set ``count`` to 0, ``memory`` to
+ ``V4L2_MEMORY_MMAP`` and ``format.type`` to the buffer type.
+ * - __u32
+ - ``reserved``\ [7]
- A place holder for future extensions. Drivers and applications
must set the array to zero.
diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
index 316f52c8a310..d4bbbb0c60e8 100644
--- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
+++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst
@@ -88,10 +88,50 @@ any DMA in progress, an implicit
``V4L2_MEMORY_DMABUF`` or ``V4L2_MEMORY_USERPTR``. See
:c:type:`v4l2_memory`.
* - __u32
- - ``reserved``\ [2]
+ - ``capabilities``
+ - Set by the driver. If 0, then the driver doesn't support
+ capabilities. In that case all you know is that the driver is
+ guaranteed to support ``V4L2_MEMORY_MMAP`` and *might* support
+ other :c:type:`v4l2_memory` types. It will not support any others
+ capabilities.
+
+ If you want to query the capabilities with a minimum of side-effects,
+ then this can be called with ``count`` set to 0, ``memory`` set to
+ ``V4L2_MEMORY_MMAP`` and ``type`` set to the buffer type. This will
+ free any previously allocated buffers, so this is typically something
+ that will be done at the start of the application.
+ * - __u32
+ - ``reserved``\ [1]
- A place holder for future extensions. Drivers and applications
must set the array to zero.
+.. tabularcolumns:: |p{6.1cm}|p{2.2cm}|p{8.7cm}|
+
+.. _v4l2-buf-capabilities:
+.. _V4L2-BUF-CAP-SUPPORTS-MMAP:
+.. _V4L2-BUF-CAP-SUPPORTS-USERPTR:
+.. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
+.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
+
+.. cssclass:: longtable
+
+.. flat-table:: V4L2 Buffer Capabilities Flags
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+ * - ``V4L2_BUF_CAP_SUPPORTS_MMAP``
+ - 0x00000001
+ - This buffer type supports the ``V4L2_MEMORY_MMAP`` streaming mode.
+ * - ``V4L2_BUF_CAP_SUPPORTS_USERPTR``
+ - 0x00000002
+ - This buffer type supports the ``V4L2_MEMORY_USERPTR`` streaming mode.
+ * - ``V4L2_BUF_CAP_SUPPORTS_DMABUF``
+ - 0x00000004
+ - This buffer type supports the ``V4L2_MEMORY_DMABUF`` streaming mode.
+ * - ``V4L2_BUF_CAP_SUPPORTS_REQUESTS``
+ - 0x00000008
+ - This buffer type supports :ref:`requests <media-request-api>`.
Return Value
============
diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
index 2350151ce4ea..55d45a387dd2 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -856,9 +856,16 @@ struct v4l2_requestbuffers {
__u32 count;
__u32 type; /* enum v4l2_buf_type */
__u32 memory; /* enum v4l2_memory */
- __u32 reserved[2];
+ __u32 capabilities;
+ __u32 reserved[1];
};
+/* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
+#define V4L2_BUF_CAP_SUPPORTS_MMAP (1 << 0)
+#define V4L2_BUF_CAP_SUPPORTS_USERPTR (1 << 1)
+#define V4L2_BUF_CAP_SUPPORTS_DMABUF (1 << 2)
+#define V4L2_BUF_CAP_SUPPORTS_REQUESTS (1 << 3)
+
/**
* struct v4l2_plane - plane info for multi-planar buffers
* @bytesused: number of bytes occupied by data in the plane (payload)
@@ -2319,6 +2326,7 @@ struct v4l2_dbg_chip_info {
* return: number of created buffers
* @memory: enum v4l2_memory; buffer memory type
* @format: frame format, for which buffers are requested
+ * @capabilities: capabilities of this buffer type.
* @reserved: future extensions
*/
struct v4l2_create_buffers {
@@ -2326,7 +2334,8 @@ struct v4l2_create_buffers {
__u32 count;
__u32 memory;
struct v4l2_format format;
- __u32 reserved[8];
+ __u32 capabilities;
+ __u32 reserved[7];
};
/*
--
2.18.0
