| .. SPDX-License-Identifier: GPL-2.0 OR GFDL-1.1-no-invariants-or-later | |
| .. c:namespace:: MC | |
| .. _request-func-ioctl: | |
| *************** | |
| request ioctl() | |
| *************** | |
| Name | |
| ==== | |
| request-ioctl - Control a request file descriptor | |
| Synopsis | |
| ======== | |
| .. code-block:: c | |
| #include <sys/ioctl.h> | |
| ``int ioctl(int fd, int cmd, void *argp)`` | |
| Arguments | |
| ========= | |
| ``fd`` | |
| File descriptor returned by :ref:`MEDIA_IOC_REQUEST_ALLOC`. | |
| ``cmd`` | |
| The request ioctl command code as defined in the media.h header file, for | |
| example :ref:`MEDIA_REQUEST_IOC_QUEUE`. | |
| ``argp`` | |
| Pointer to a request-specific structure. | |
| Description | |
| =========== | |
| The :ref:`ioctl() <request-func-ioctl>` function manipulates request | |
| parameters. The argument ``fd`` must be an open file descriptor. | |
| The ioctl ``cmd`` code specifies the request 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 request ioctl commands and | |
| their parameters are located in the media.h header file. All request ioctl | |
| commands, their respective function and parameters are specified in | |
| :ref:`media-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. | |
| Command-specific error codes are listed in the individual command | |
| descriptions. | |
| When an ioctl that takes an output or read/write parameter fails, the | |
| parameter remains unmodified. |