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