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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_SUBDEV_G_CLIENT_CAP:
+
+************************************************************
+ioctl VIDIOC_SUBDEV_G_CLIENT_CAP, VIDIOC_SUBDEV_S_CLIENT_CAP
+************************************************************
+
+Name
+====
+
+VIDIOC_SUBDEV_G_CLIENT_CAP - VIDIOC_SUBDEV_S_CLIENT_CAP - Get or set client
+capabilities.
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_SUBDEV_G_CLIENT_CAP
+
+``int ioctl(int fd, VIDIOC_SUBDEV_G_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)``
+
+.. c:macro:: VIDIOC_SUBDEV_S_CLIENT_CAP
+
+``int ioctl(int fd, VIDIOC_SUBDEV_S_CLIENT_CAP, struct v4l2_subdev_client_capability *argp)``
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :ref:`open() <func-open>`.
+
+``argp``
+    Pointer to struct :c:type:`v4l2_subdev_client_capability`.
+
+Description
+===========
+
+These ioctls are used to get and set the client (the application using the
+subdevice ioctls) capabilities. The client capabilities are stored in the file
+handle of the opened subdev device node, and the client must set the
+capabilities for each opened subdev separately.
+
+By default no client capabilities are set when a subdev device node is opened.
+
+The purpose of the client capabilities are to inform the kernel of the behavior
+of the client, mainly related to maintaining compatibility with different
+kernel and userspace versions.
+
+The ``VIDIOC_SUBDEV_G_CLIENT_CAP`` ioctl returns the current client capabilities
+associated with the file handle ``fd``.
+
+The ``VIDIOC_SUBDEV_S_CLIENT_CAP`` ioctl sets client capabilities for the file
+handle ``fd``. The new capabilities fully replace the current capabilities, the
+ioctl can therefore also be used to remove capabilities that have previously
+been set.
+
+``VIDIOC_SUBDEV_S_CLIENT_CAP`` modifies the struct
+:c:type:`v4l2_subdev_client_capability` to reflect the capabilities that have
+been accepted. A common case for the kernel not accepting a capability is that
+the kernel is older than the headers the userspace uses, and thus the capability
+is unknown to the kernel.
+
+.. tabularcolumns:: |p{1.5cm}|p{2.9cm}|p{12.9cm}|
+
+.. c:type:: v4l2_subdev_client_capability
+
+.. flat-table:: struct v4l2_subdev_client_capability
+    :header-rows:  0
+    :stub-columns: 0
+    :widths:       3 4 20
+
+    * - __u64
+      - ``capabilities``
+      - Sub-device client capabilities of the opened device.
+
+.. tabularcolumns:: |p{6.8cm}|p{2.4cm}|p{8.1cm}|
+
+.. flat-table:: Client Capabilities
+    :header-rows:  1
+
+    * - Capability
+      - Description
+    * - ``V4L2_SUBDEV_CLIENT_CAP_STREAMS``
+      - The client is aware of streams. Setting this flag enables the use
+        of 'stream' fields (referring to the stream number) with various
+        ioctls. If this is not set (which is the default), the 'stream' fields
+        will be forced to 0 by the kernel.
+    * - ``V4L2_SUBDEV_CLIENT_CAP_INTERVAL_USES_WHICH``
+      - The client is aware of the :c:type:`v4l2_subdev_frame_interval`
+        ``which`` field. If this is not set (which is the default), the
+        ``which`` field is forced to ``V4L2_SUBDEV_FORMAT_ACTIVE`` by the
+        kernel.
+
+Return Value
+============
+
+On success 0 is returned, on error -1 and the ``errno`` variable is set
+appropriately. The generic error codes are described at the
+:ref:`Generic Error Codes <gen-errors>` chapter.
+
+ENOIOCTLCMD
+   The kernel does not support this ioctl.