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| -rw-r--r-- | Documentation/media/uapi/v4l/vidioc-g-frequency.rst | 105 |
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diff --git a/Documentation/media/uapi/v4l/vidioc-g-frequency.rst b/Documentation/media/uapi/v4l/vidioc-g-frequency.rst new file mode 100644 index 000000000..c1cccb144 --- /dev/null +++ b/Documentation/media/uapi/v4l/vidioc-g-frequency.rst @@ -0,0 +1,105 @@ +.. -*- 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() <func-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 <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 <VIDIOC_G_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 <VIDIOC_G_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 <gen-errors>` 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. |