| .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later |
| .. c:namespace:: V4L |
| |
| .. _VIDIOC_G_OUTPUT: |
| |
| ************************************** |
| ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT |
| ************************************** |
| |
| Name |
| ==== |
| |
| VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output |
| |
| Synopsis |
| ======== |
| |
| .. c:macro:: VIDIOC_G_OUTPUT |
| |
| ``int ioctl(int fd, VIDIOC_G_OUTPUT, int *argp)`` |
| |
| .. c:macro:: VIDIOC_S_OUTPUT |
| |
| ``int ioctl(int fd, VIDIOC_S_OUTPUT, int *argp)`` |
| |
| Arguments |
| ========= |
| |
| ``fd`` |
| File descriptor returned by :c:func:`open()`. |
| |
| ``argp`` |
| Pointer to an integer with output index. |
| |
| Description |
| =========== |
| |
| To query the current video output applications call the |
| :ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver |
| stores the number of the output, as in the struct |
| :c:type:`v4l2_output` ``index`` field. This ioctl will |
| fail only when there are no video outputs, returning the ``EINVAL`` error |
| code. |
| |
| To select a video output applications store the number of the desired |
| output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a |
| pointer to this integer. Side effects are possible. For example outputs |
| may support different video standards, so the driver may implicitly |
| switch the current standard. standard. Because of these possible side |
| effects applications must select an output before querying or |
| negotiating any other parameters. |
| |
| Information about video outputs is available using the |
| :ref:`VIDIOC_ENUMOUTPUT` ioctl. |
| |
| 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. |
| |
| EINVAL |
| The number of the video output is out of bounds, or there are no |
| video outputs at all. |