media: videodev2.h: add new capabilities for buffer types

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@cisco.com>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Acked-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

2 files changed, 54 insertions, 2 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
 ============