Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst
.. SPDX-License-Identifier: GPL-2.0
.. _GPIO_GET_LINEEVENT_IOCTL:
GPIO_GET_LINEEVENT_IOCTL
.. warning:: This ioctl is part of chardev_v1.rst and is obsoleted by gpio-v2-get-line-ioctl.rst.
GPIO_GET_LINEEVENT_IOCTL - Request a line with edge detection from the kernel.
.. c:macro:: GPIO_GET_LINEEVENT_IOCTL
int ioctl(int chip_fd, GPIO_GET_LINEEVENT_IOCTL, struct gpioevent_request *request)
chip_fd
The file descriptor of the GPIO character device returned by open().
request
The :c:type:event_request<gpioevent_request> specifying the line
to request and its configuration.
Request a line with edge detection from the kernel.
On success, the requesting process is granted exclusive access to the line value and may receive events when edges are detected on the line, as described in gpio-lineevent-data-read.rst.
The state of a line 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).
Requesting edge detection on a line that does not support interrupts is an error (ENXIO).
As with the :ref:line handle<gpio-get-linehandle-config-support>, the
bias configuration is best effort.
Closing the chip_fd has no effect on existing line events.
The following configuration rules apply:
The line event is requested as an input, so no flags specific to output lines,
GPIOHANDLE_REQUEST_OUTPUT, GPIOHANDLE_REQUEST_OPEN_DRAIN, or
GPIOHANDLE_REQUEST_OPEN_SOURCE, may be set.
Only one bias flag, GPIOHANDLE_REQUEST_BIAS_xxx, may be set.
If no bias flags are set then the bias configuration is not changed.
The edge flags, GPIOEVENT_REQUEST_RISING_EDGE and
GPIOEVENT_REQUEST_FALLING_EDGE, may be combined to detect both rising
and falling edges.
Requesting an invalid configuration is an error (EINVAL).
On success 0 and the :c:type:request.fd<gpioevent_request> contains the file
descriptor for the request.
On error -1 and the errno variable is set appropriately.
Common error codes are described in error-codes.rst.