vidioc-g-frequency.rst

  1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
  2.. c:namespace:: V4L
  3
  4.. _VIDIOC_G_FREQUENCY:
  5
  6********************************************
  7ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY
  8********************************************
  9
 10Name
 11====
 12
 13VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency
 14
 15Synopsis
 16========
 17
 18.. c:macro:: VIDIOC_G_FREQUENCY
 19
 20``int ioctl(int fd, VIDIOC_G_FREQUENCY, struct v4l2_frequency *argp)``
 21
 22.. c:macro:: VIDIOC_S_FREQUENCY
 23
 24``int ioctl(int fd, VIDIOC_S_FREQUENCY, const struct v4l2_frequency *argp)``
 25
 26Arguments
 27=========
 28
 29``fd``
 30    File descriptor returned by :c:func:`open()`.
 31
 32``argp``
 33    Pointer to struct :c:type:`v4l2_frequency`.
 34
 35Description
 36===========
 37
 38To get the current tuner or modulator radio frequency applications set
 39the ``tuner`` field of a struct
 40:c:type:`v4l2_frequency` to the respective tuner or
 41modulator number (only input devices have tuners, only output devices
 42have modulators), zero out the ``reserved`` array and call the
 43:ref:`VIDIOC_G_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this structure. The
 44driver stores the current frequency in the ``frequency`` field.
 45
 46To change the current tuner or modulator radio frequency applications
 47initialize the ``tuner``, ``type`` and ``frequency`` fields, and the
 48``reserved`` array of a struct :c:type:`v4l2_frequency`
 49and call the :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` ioctl with a pointer to this
 50structure. When the requested frequency is not possible the driver
 51assumes the closest possible value. However :ref:`VIDIOC_S_FREQUENCY <VIDIOC_G_FREQUENCY>` is a
 52write-only ioctl, it does not return the actual new frequency.
 53
 54.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
 55
 56.. c:type:: v4l2_frequency
 57
 58.. flat-table:: struct v4l2_frequency
 59    :header-rows:  0
 60    :stub-columns: 0
 61    :widths:       1 1 2
 62
 63    * - __u32
 64      - ``tuner``
 65      - The tuner or modulator index number. This is the same value as in
 66	the struct :c:type:`v4l2_input` ``tuner`` field and
 67	the struct :c:type:`v4l2_tuner` ``index`` field, or
 68	the struct :c:type:`v4l2_output` ``modulator`` field
 69	and the struct :c:type:`v4l2_modulator` ``index``
 70	field.
 71    * - __u32
 72      - ``type``
 73      - The tuner type. This is the same value as in the struct
 74	:c:type:`v4l2_tuner` ``type`` field. The type must be
 75	set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and
 76	to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to
 77	``V4L2_TUNER_RADIO`` for modulators (currently only radio
 78	modulators are supported). See :c:type:`v4l2_tuner_type`
 79    * - __u32
 80      - ``frequency``
 81      - Tuning frequency in units of 62.5 kHz, or if the struct
 82	:c:type:`v4l2_tuner` or struct
 83	:c:type:`v4l2_modulator` ``capability`` flag
 84	``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is
 85	used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set.
 86    * - __u32
 87      - ``reserved``\ [8]
 88      - Reserved for future extensions. Drivers and applications must set
 89	the array to zero.
 90
 91Return Value
 92============
 93
 94On success 0 is returned, on error -1 and the ``errno`` variable is set
 95appropriately. The generic error codes are described at the
 96:ref:`Generic Error Codes <gen-errors>` chapter.
 97
 98EINVAL
 99    The ``tuner`` index is out of bounds or the value in the ``type``
100    field is wrong.
101
102EBUSY
103    A hardware seek is in progress.