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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: CEC
+
+.. _cec-func-ioctl:
+
+***********
+cec ioctl()
+***********
+
+Name
+====
+
+cec-ioctl - Control a cec device
+
+Synopsis
+========
+
+.. code-block:: c
+
+    #include <sys/ioctl.h>
+
+``int ioctl(int fd, int request, void *argp)``
+
+Arguments
+=========
+
+``fd``
+    File descriptor returned by :c:func:`open()`.
+
+``request``
+    CEC ioctl request code as defined in the cec.h header file, for
+    example :ref:`CEC_ADAP_G_CAPS <CEC_ADAP_G_CAPS>`.
+
+``argp``
+    Pointer to a request-specific structure.
+
+Description
+===========
+
+The :c:func:`ioctl()` function manipulates cec device parameters. The
+argument ``fd`` must be an open file descriptor.
+
+The ioctl ``request`` code specifies the cec function to be called. It
+has encoded in it whether the argument is an input, output or read/write
+parameter, and the size of the argument ``argp`` in bytes.
+
+Macros and structures definitions specifying cec ioctl requests and
+their parameters are located in the cec.h header file. All cec ioctl
+requests, their respective function and parameters are specified in
+:ref:`cec-user-func`.
+
+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.
+
+Request-specific error codes are listed in the individual requests
+descriptions.
+
+When an ioctl that takes an output or read/write parameter fails, the
+parameter remains unmodified.