Documentation/userspace-api/gpio/gpio-v2-get-line-ioctl.rst

Source file repositories/reference/linux-study-clean/Documentation/userspace-api/gpio/gpio-v2-get-line-ioctl.rst

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Linux kernel
Corpus path
Documentation/userspace-api/gpio/gpio-v2-get-line-ioctl.rst
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.rst
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5557 bytes
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153
Domain
Support Tooling And Documentation
Bucket
Documentation
Inferred role
Support Tooling And Documentation: documentation
Status
atlas-only

Why This File Exists

Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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Detected Declarations

Annotated Snippet

.. SPDX-License-Identifier: GPL-2.0

.. _GPIO_V2_GET_LINE_IOCTL:

**********************
GPIO_V2_GET_LINE_IOCTL
**********************

Name
====

GPIO_V2_GET_LINE_IOCTL - Request a line or lines from the kernel.

Synopsis
========

.. c:macro:: GPIO_V2_GET_LINE_IOCTL

``int ioctl(int chip_fd, GPIO_V2_GET_LINE_IOCTL, struct gpio_v2_line_request *request)``

Arguments
=========

``chip_fd``
    The file descriptor of the GPIO character device returned by `open()`.

``request``
    The :c:type:`line_request<gpio_v2_line_request>` specifying the lines
    to request and their configuration.

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

On success, the requesting process is granted exclusive access to the line
value, write access to the line configuration, and may receive events when
edges are detected on the line, all of which are described in more detail in
:ref:`gpio-v2-line-request`.

A number of lines may be requested in the one line request, and request
operations are performed on the requested lines by the kernel as atomically
as possible. e.g. gpio-v2-line-get-values-ioctl.rst will read all the
requested lines at once.

The state of a line, including the value of output lines, is guaranteed to
remain as requested until the returned file descriptor is closed. Once the
file descriptor is closed, the state of the line becomes uncontrolled from
the userspace perspective, and may revert to its default state.

Requesting a line already in use is an error (**EBUSY**).

Closing the ``chip_fd`` has no effect on existing line requests.

.. _gpio-v2-get-line-config-rules:

Configuration Rules
-------------------

For any given requested line, the following configuration rules apply:

The direction flags, ``GPIO_V2_LINE_FLAG_INPUT`` and
``GPIO_V2_LINE_FLAG_OUTPUT``, cannot be combined. If neither are set then
the only other flag that may be set is ``GPIO_V2_LINE_FLAG_ACTIVE_LOW``
and the line is requested "as-is" to allow reading of the line value
without altering the electrical configuration.

The drive flags, ``GPIO_V2_LINE_FLAG_OPEN_xxx``, require the
``GPIO_V2_LINE_FLAG_OUTPUT`` to be set.
Only one drive flag may be set.
If none are set then the line is assumed push-pull.

Annotation

Implementation Notes