linux/Documentation/userspace-api/gpio/gpio-handle-get-line-values-ioctl.rst

.. SPDX-License-Identifier: GPL-2.0

.. _GPIOHANDLE_GET_LINE_VALUES_IOCTL:

********************************
GPIOHANDLE_GET_LINE_VALUES_IOCTL
********************************
.. warning::
    This ioctl is part of chardev_v1.rst and is obsoleted by
    gpio-v2-line-get-values-ioctl.rst.

Name
====

GPIOHANDLE_GET_LINE_VALUES_IOCTL - Get the values of all requested lines.

Synopsis
========

.. c:macro:: GPIOHANDLE_GET_LINE_VALUES_IOCTL

``int ioctl(int handle_fd, GPIOHANDLE_GET_LINE_VALUES_IOCTL, struct gpiohandle_data *values)``

Arguments
=========

``handle_fd``
    The file descriptor of the GPIO character device, as returned in the
    :c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst.

``values``
    The :c:type:`line_values<gpiohandle_data>` to be populated.

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

Get the values of all requested lines.

The values returned are logical, indicating if the line is active or inactive.
The ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` flag controls the mapping between physical
values (high/low) and logical values (active/inactive).
If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is not set then high is active and
low is inactive. If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is set then low is active
and high is inactive.

The values of both input and output lines may be read.

For output lines, the value returned is driver and configuration dependent and
may be either the output buffer (the last requested value set) or the input
buffer (the actual level of the line), and depending on the hardware and
configuration these may differ.

This ioctl can also be used to read the line value for line events,
substituting the ``event_fd`` for the ``handle_fd``.  As there is only
one line requested in that case, only the one value is returned in ``values``.

Return Value
============

On success 0 and ``values`` populated with the values read.

On error -1 and the ``errno`` variable is set appropriately.
Common error codes are described in error-codes.rst.