141 lines
4.4 KiB
ReStructuredText
141 lines
4.4 KiB
ReStructuredText
.. -*- coding: utf-8; mode: rst -*-
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.. _VIDIOC_S_HW_FREQ_SEEK:
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***************************
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ioctl VIDIOC_S_HW_FREQ_SEEK
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***************************
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Name
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====
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VIDIOC_S_HW_FREQ_SEEK - Perform a hardware frequency seek
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Synopsis
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========
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.. c:function:: int ioctl( int fd, VIDIOC_S_HW_FREQ_SEEK, struct v4l2_hw_freq_seek *argp )
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:name: VIDIOC_S_HW_FREQ_SEEK
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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_hw_freq_seek`.
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Description
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===========
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Start a hardware frequency seek from the current frequency. To do this
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applications initialize the ``tuner``, ``type``, ``seek_upward``,
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``wrap_around``, ``spacing``, ``rangelow`` and ``rangehigh`` fields, and
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zero out the ``reserved`` array of a struct
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:c:type:`v4l2_hw_freq_seek` and call the
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``VIDIOC_S_HW_FREQ_SEEK`` ioctl with a pointer to this structure.
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The ``rangelow`` and ``rangehigh`` fields can be set to a non-zero value
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to tell the driver to search a specific band. If the struct
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:c:type:`v4l2_tuner` ``capability`` field has the
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``V4L2_TUNER_CAP_HWSEEK_PROG_LIM`` flag set, these values must fall
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within one of the bands returned by
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:ref:`VIDIOC_ENUM_FREQ_BANDS`. If the
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``V4L2_TUNER_CAP_HWSEEK_PROG_LIM`` flag is not set, then these values
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must exactly match those of one of the bands returned by
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:ref:`VIDIOC_ENUM_FREQ_BANDS`. If the
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current frequency of the tuner does not fall within the selected band it
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will be clamped to fit in the band before the seek is started.
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If an error is returned, then the original frequency will be restored.
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This ioctl is supported if the ``V4L2_CAP_HW_FREQ_SEEK`` capability is
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set.
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If this ioctl is called from a non-blocking filehandle, then ``EAGAIN``
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error code is returned and no seek takes place.
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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
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.. c:type:: v4l2_hw_freq_seek
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.. flat-table:: struct v4l2_hw_freq_seek
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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 index number. This is the same value as in the struct
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:c:type:`v4l2_input` ``tuner`` field and the struct
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:c:type:`v4l2_tuner` ``index`` 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. See
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:c:type:`v4l2_tuner_type`
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* - __u32
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- ``seek_upward``
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- If non-zero, seek upward from the current frequency, else seek
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downward.
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* - __u32
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- ``wrap_around``
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- If non-zero, wrap around when at the end of the frequency range,
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else stop seeking. The struct :c:type:`v4l2_tuner`
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``capability`` field will tell you what the hardware supports.
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* - __u32
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- ``spacing``
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- If non-zero, defines the hardware seek resolution in Hz. The
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driver selects the nearest value that is supported by the device.
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If spacing is zero a reasonable default value is used.
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* - __u32
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- ``rangelow``
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- If non-zero, the lowest tunable frequency of the band to search in
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units of 62.5 kHz, or if the struct
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:c:type:`v4l2_tuner` ``capability`` field has the
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``V4L2_TUNER_CAP_LOW`` flag set, in units of 62.5 Hz or if the
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struct :c:type:`v4l2_tuner` ``capability`` field has
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the ``V4L2_TUNER_CAP_1HZ`` flag set, in units of 1 Hz. If
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``rangelow`` is zero a reasonable default value is used.
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* - __u32
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- ``rangehigh``
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- If non-zero, the highest tunable frequency of the band to search
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in units of 62.5 kHz, or if the struct
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:c:type:`v4l2_tuner` ``capability`` field has the
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``V4L2_TUNER_CAP_LOW`` flag set, in units of 62.5 Hz or if the
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struct :c:type:`v4l2_tuner` ``capability`` field has
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the ``V4L2_TUNER_CAP_1HZ`` flag set, in units of 1 Hz. If
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``rangehigh`` is zero a reasonable default value is used.
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* - __u32
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- ``reserved``\ [5]
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- Reserved for future extensions. Applications must set the array to
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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, the ``wrap_around`` value is
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not supported or one of the values in the ``type``, ``rangelow`` or
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``rangehigh`` fields is wrong.
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EAGAIN
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Attempted to call ``VIDIOC_S_HW_FREQ_SEEK`` with the filehandle in
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non-blocking mode.
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ENODATA
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The hardware seek found no channels.
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EBUSY
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Another hardware seek is already in progress.
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