Documentation/userspace-api/media/v4l/vidioc-s-hw-freq-seek.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/media/v4l/vidioc-s-hw-freq-seek.rst

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Linux kernel
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Documentation/userspace-api/media/v4l/vidioc-s-hw-freq-seek.rst
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.rst
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4540 bytes
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Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
.. c:namespace:: V4L

.. _VIDIOC_S_HW_FREQ_SEEK:

***************************
ioctl VIDIOC_S_HW_FREQ_SEEK
***************************

Name
====

VIDIOC_S_HW_FREQ_SEEK - Perform a hardware frequency seek

Synopsis
========

.. c:macro:: VIDIOC_S_HW_FREQ_SEEK

``int ioctl(int fd, VIDIOC_S_HW_FREQ_SEEK, struct v4l2_hw_freq_seek *argp)``

Arguments
=========

``fd``
    File descriptor returned by :c:func:`open()`.

``argp``
    Pointer to struct :c:type:`v4l2_hw_freq_seek`.

Description
===========

Start a hardware frequency seek from the current frequency. To do this
applications initialize the ``tuner``, ``type``, ``seek_upward``,
``wrap_around``, ``spacing``, ``rangelow`` and ``rangehigh`` fields, and
zero out the ``reserved`` array of a struct
:c:type:`v4l2_hw_freq_seek` and call the
``VIDIOC_S_HW_FREQ_SEEK`` ioctl with a pointer to this structure.

The ``rangelow`` and ``rangehigh`` fields can be set to a non-zero value
to tell the driver to search a specific band. If the struct
:c:type:`v4l2_tuner` ``capability`` field has the
``V4L2_TUNER_CAP_HWSEEK_PROG_LIM`` flag set, these values must fall
within one of the bands returned by
:ref:`VIDIOC_ENUM_FREQ_BANDS`. If the
``V4L2_TUNER_CAP_HWSEEK_PROG_LIM`` flag is not set, then these values
must exactly match those of one of the bands returned by
:ref:`VIDIOC_ENUM_FREQ_BANDS`. If the
current frequency of the tuner does not fall within the selected band it
will be clamped to fit in the band before the seek is started.

If an error is returned, then the original frequency will be restored.

This ioctl is supported if the ``V4L2_CAP_HW_FREQ_SEEK`` capability is
set.

If this ioctl is called from a non-blocking filehandle, then ``EAGAIN``
error code is returned and no seek takes place.

.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|

.. c:type:: v4l2_hw_freq_seek

.. flat-table:: struct v4l2_hw_freq_seek
    :header-rows:  0
    :stub-columns: 0
    :widths:       1 1 2

    * - __u32

Annotation

Implementation Notes