1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2 .. c:namespace:: V4L 3 4 .. _VIDIOC_G_OUTPUT: 5 6 ************************************** 7 ioctl VIDIOC_G_OUTPUT, VIDIOC_S_OUTPUT 8 ************************************** 9 10 Name 11 ==== 12 13 VIDIOC_G_OUTPUT - VIDIOC_S_OUTPUT - Query or select the current video output 14 15 Synopsis 16 ======== 17 18 .. c:macro:: VIDIOC_G_OUTPUT 19 20 ``int ioctl(int fd, VIDIOC_G_OUTPUT, int *argp)`` 21 22 .. c:macro:: VIDIOC_S_OUTPUT 23 24 ``int ioctl(int fd, VIDIOC_S_OUTPUT, int *argp)`` 25 26 Arguments 27 ========= 28 29 ``fd`` 30 File descriptor returned by :c:func:`open()`. 31 32 ``argp`` 33 Pointer to an integer with output index. 34 35 Description 36 =========== 37 38 To query the current video output applications call the 39 :ref:`VIDIOC_G_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a pointer to an integer where the driver 40 stores the number of the output, as in the struct 41 :c:type:`v4l2_output` ``index`` field. This ioctl will 42 fail only when there are no video outputs, returning the ``EINVAL`` error 43 code. 44 45 To select a video output applications store the number of the desired 46 output in an integer and call the :ref:`VIDIOC_S_OUTPUT <VIDIOC_G_OUTPUT>` ioctl with a 47 pointer to this integer. Side effects are possible. For example outputs 48 may support different video standards, so the driver may implicitly 49 switch the current standard. Because of these possible side 50 effects applications must select an output before querying or 51 negotiating any other parameters. 52 53 Information about video outputs is available using the 54 :ref:`VIDIOC_ENUMOUTPUT` ioctl. 55 56 Return Value 57 ============ 58 59 On success 0 is returned, on error -1 and the ``errno`` variable is set 60 appropriately. The generic error codes are described at the 61 :ref:`Generic Error Codes <gen-errors>` chapter. 62 63 EINVAL 64 The number of the video output is out of bounds, or there are no 65 video outputs at all.
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