.. -*- coding: utf-8; mode: rst -*- .. _VIDIOC_G_FREQUENCY: ******************************************** ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY ******************************************** Name ==== VIDIOC_G_FREQUENCY - VIDIOC_S_FREQUENCY - Get or set tuner or modulator radio frequency Synopsis ======== .. c:function:: int ioctl( int fd, VIDIOC_G_FREQUENCY, struct v4l2_frequency *argp ) :name: VIDIOC_G_FREQUENCY .. c:function:: int ioctl( int fd, VIDIOC_S_FREQUENCY, const struct v4l2_frequency *argp ) :name: VIDIOC_S_FREQUENCY Arguments ========= ``fd`` File descriptor returned by :ref:`open() `. ``argp`` Pointer to struct :c:type:`v4l2_frequency`. Description =========== To get the current tuner or modulator radio frequency applications set the ``tuner`` field of a struct :c:type:`v4l2_frequency` to the respective tuner or modulator number (only input devices have tuners, only output devices have modulators), zero out the ``reserved`` array and call the :ref:`VIDIOC_G_FREQUENCY ` ioctl with a pointer to this structure. The driver stores the current frequency in the ``frequency`` field. To change the current tuner or modulator radio frequency applications initialize the ``tuner``, ``type`` and ``frequency`` fields, and the ``reserved`` array of a struct :c:type:`v4l2_frequency` and call the :ref:`VIDIOC_S_FREQUENCY ` ioctl with a pointer to this structure. When the requested frequency is not possible the driver assumes the closest possible value. However :ref:`VIDIOC_S_FREQUENCY ` is a write-only ioctl, it does not return the actual new frequency. .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| .. c:type:: v4l2_frequency .. flat-table:: struct v4l2_frequency :header-rows: 0 :stub-columns: 0 :widths: 1 1 2 * - __u32 - ``tuner`` - The tuner or modulator index number. This is the same value as in the struct :c:type:`v4l2_input` ``tuner`` field and the struct :c:type:`v4l2_tuner` ``index`` field, or the struct :c:type:`v4l2_output` ``modulator`` field and the struct :c:type:`v4l2_modulator` ``index`` field. * - __u32 - ``type`` - The tuner type. This is the same value as in the struct :c:type:`v4l2_tuner` ``type`` field. The type must be set to ``V4L2_TUNER_RADIO`` for ``/dev/radioX`` device nodes, and to ``V4L2_TUNER_ANALOG_TV`` for all others. Set this field to ``V4L2_TUNER_RADIO`` for modulators (currently only radio modulators are supported). See :c:type:`v4l2_tuner_type` * - __u32 - ``frequency`` - Tuning frequency in units of 62.5 kHz, or if the struct :c:type:`v4l2_tuner` or struct :c:type:`v4l2_modulator` ``capability`` flag ``V4L2_TUNER_CAP_LOW`` is set, in units of 62.5 Hz. A 1 Hz unit is used when the ``capability`` flag ``V4L2_TUNER_CAP_1HZ`` is set. * - __u32 - ``reserved``\ [8] - Reserved for future extensions. Drivers and applications must set the array to zero. 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 ` chapter. EINVAL The ``tuner`` index is out of bounds or the value in the ``type`` field is wrong. EBUSY A hardware seek is in progress.