Markus Heiser | 5377d91 | 2016-06-30 15:18:56 +0200 | [diff] [blame^] | 1 | .. -*- coding: utf-8; mode: rst -*- |
| 2 | |
| 3 | .. _vidioc-g-frequency: |
| 4 | |
| 5 | ******************************************** |
| 6 | ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY |
| 7 | ******************************************** |
| 8 | |
| 9 | *man VIDIOC_G_FREQUENCY(2)* |
| 10 | |
| 11 | VIDIOC_S_FREQUENCY |
| 12 | Get or set tuner or modulator radio frequency |
| 13 | |
| 14 | |
| 15 | Synopsis |
| 16 | ======== |
| 17 | |
| 18 | .. c:function:: int ioctl( int fd, int request, struct v4l2_frequency *argp ) |
| 19 | |
| 20 | .. c:function:: int ioctl( int fd, int request, const struct v4l2_frequency *argp ) |
| 21 | |
| 22 | Arguments |
| 23 | ========= |
| 24 | |
| 25 | ``fd`` |
| 26 | File descriptor returned by :ref:`open() <func-open>`. |
| 27 | |
| 28 | ``request`` |
| 29 | VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY |
| 30 | |
| 31 | ``argp`` |
| 32 | |
| 33 | |
| 34 | Description |
| 35 | =========== |
| 36 | |
| 37 | To get the current tuner or modulator radio frequency applications set |
| 38 | the ``tuner`` field of a struct |
| 39 | :ref:`v4l2_frequency <v4l2-frequency>` to the respective tuner or |
| 40 | modulator number (only input devices have tuners, only output devices |
| 41 | have modulators), zero out the ``reserved`` array and call the |
| 42 | ``VIDIOC_G_FREQUENCY`` ioctl with a pointer to this structure. The |
| 43 | driver stores the current frequency in the ``frequency`` field. |
| 44 | |
| 45 | To change the current tuner or modulator radio frequency applications |
| 46 | initialize the ``tuner``, ``type`` and ``frequency`` fields, and the |
| 47 | ``reserved`` array of a struct :ref:`v4l2_frequency <v4l2-frequency>` |
| 48 | and call the ``VIDIOC_S_FREQUENCY`` ioctl with a pointer to this |
| 49 | structure. When the requested frequency is not possible the driver |
| 50 | assumes the closest possible value. However ``VIDIOC_S_FREQUENCY`` is a |
| 51 | write-only ioctl, it does not return the actual new frequency. |
| 52 | |
| 53 | |
| 54 | .. _v4l2-frequency: |
| 55 | |
| 56 | .. flat-table:: struct v4l2_frequency |
| 57 | :header-rows: 0 |
| 58 | :stub-columns: 0 |
| 59 | :widths: 1 1 2 |
| 60 | |
| 61 | |
| 62 | - .. row 1 |
| 63 | |
| 64 | - __u32 |
| 65 | |
| 66 | - ``tuner`` |
| 67 | |
| 68 | - The tuner or modulator index number. This is the same value as in |
| 69 | the struct :ref:`v4l2_input <v4l2-input>` ``tuner`` field and |
| 70 | the struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` field, or |
| 71 | the struct :ref:`v4l2_output <v4l2-output>` ``modulator`` field |
| 72 | and the struct :ref:`v4l2_modulator <v4l2-modulator>` ``index`` |
| 73 | field. |
| 74 | |
| 75 | - .. row 2 |
| 76 | |
| 77 | - __u32 |
| 78 | |
| 79 | - ``type`` |
| 80 | |
| 81 | - The tuner type. This is the same value as in the struct |
| 82 | :ref:`v4l2_tuner <v4l2-tuner>` ``type`` field. The type must be |
| 83 | set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and |
| 84 | to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to |
| 85 | ``V4L2_TUNER_RADIO`` for modulators (currently only radio |
| 86 | modulators are supported). See :ref:`v4l2-tuner-type` |
| 87 | |
| 88 | - .. row 3 |
| 89 | |
| 90 | - __u32 |
| 91 | |
| 92 | - ``frequency`` |
| 93 | |
| 94 | - Tuning frequency in units of 62.5 kHz, or if the struct |
| 95 | :ref:`v4l2_tuner <v4l2-tuner>` or struct |
| 96 | :ref:`v4l2_modulator <v4l2-modulator>` ``capability`` flag |
| 97 | ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is |
| 98 | used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set. |
| 99 | |
| 100 | - .. row 4 |
| 101 | |
| 102 | - __u32 |
| 103 | |
| 104 | - ``reserved``\ [8] |
| 105 | |
| 106 | - Reserved for future extensions. Drivers and applications must set |
| 107 | the array to zero. |
| 108 | |
| 109 | |
| 110 | |
| 111 | Return Value |
| 112 | ============ |
| 113 | |
| 114 | On success 0 is returned, on error -1 and the ``errno`` variable is set |
| 115 | appropriately. The generic error codes are described at the |
| 116 | :ref:`Generic Error Codes <gen-errors>` chapter. |
| 117 | |
| 118 | EINVAL |
| 119 | The ``tuner`` index is out of bounds or the value in the ``type`` |
| 120 | field is wrong. |
| 121 | |
| 122 | EBUSY |
| 123 | A hardware seek is in progress. |
| 124 | |
| 125 | |
| 126 | .. ------------------------------------------------------------------------------ |
| 127 | .. This file was automatically converted from DocBook-XML with the dbxml |
| 128 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes |
| 129 | .. from the linux kernel, refer to: |
| 130 | .. |
| 131 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook |
| 132 | .. ------------------------------------------------------------------------------ |