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Diffstat (limited to 'Documentation/linux_tv/media/v4l/vidioc-g-frequency.rst')
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diff --git a/Documentation/linux_tv/media/v4l/vidioc-g-frequency.rst b/Documentation/linux_tv/media/v4l/vidioc-g-frequency.rst new file mode 100644 index 0000000..1d9f0fe --- /dev/null +++ b/Documentation/linux_tv/media/v4l/vidioc-g-frequency.rst @@ -0,0 +1,132 @@ +.. -*- coding: utf-8; mode: rst -*- + +.. _vidioc-g-frequency: + +******************************************** +ioctl VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY +******************************************** + +*man VIDIOC_G_FREQUENCY(2)* + +VIDIOC_S_FREQUENCY +Get or set tuner or modulator radio frequency + + +Synopsis +======== + +.. c:function:: int ioctl( int fd, int request, struct v4l2_frequency *argp ) + +.. c:function:: int ioctl( int fd, int request, const struct v4l2_frequency *argp ) + +Arguments +========= + +``fd`` + File descriptor returned by :ref:`open() <func-open>`. + +``request`` + VIDIOC_G_FREQUENCY, VIDIOC_S_FREQUENCY + +``argp`` + + +Description +=========== + +To get the current tuner or modulator radio frequency applications set +the ``tuner`` field of a struct +:ref:`v4l2_frequency <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 +``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 :ref:`v4l2_frequency <v4l2-frequency>` +and call the ``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 ``VIDIOC_S_FREQUENCY`` is a +write-only ioctl, it does not return the actual new frequency. + + +.. _v4l2-frequency: + +.. flat-table:: struct v4l2_frequency + :header-rows: 0 + :stub-columns: 0 + :widths: 1 1 2 + + + - .. row 1 + + - __u32 + + - ``tuner`` + + - The tuner or modulator index number. This is the same value as in + the struct :ref:`v4l2_input <v4l2-input>` ``tuner`` field and + the struct :ref:`v4l2_tuner <v4l2-tuner>` ``index`` field, or + the struct :ref:`v4l2_output <v4l2-output>` ``modulator`` field + and the struct :ref:`v4l2_modulator <v4l2-modulator>` ``index`` + field. + + - .. row 2 + + - __u32 + + - ``type`` + + - The tuner type. This is the same value as in the struct + :ref:`v4l2_tuner <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 :ref:`v4l2-tuner-type` + + - .. row 3 + + - __u32 + + - ``frequency`` + + - Tuning frequency in units of 62.5 kHz, or if the struct + :ref:`v4l2_tuner <v4l2-tuner>` or struct + :ref:`v4l2_modulator <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. + + - .. row 4 + + - __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. + + +.. ------------------------------------------------------------------------------ +.. This file was automatically converted from DocBook-XML with the dbxml +.. library (https://github.com/return42/sphkerneldoc). The origin XML comes +.. from the linux kernel, refer to: +.. +.. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook +.. ------------------------------------------------------------------------------ |