summaryrefslogtreecommitdiff
path: root/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst')
-rw-r--r--Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst84
1 files changed, 84 insertions, 0 deletions
diff --git a/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst
new file mode 100644
index 000000000000..09a9254f38cf
--- /dev/null
+++ b/Documentation/userspace-api/gpio/gpio-get-lineevent-ioctl.rst
@@ -0,0 +1,84 @@
+.. 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.
+
+Name
+====
+
+GPIO_GET_LINEEVENT_IOCTL - Request a line with edge detection from the kernel.
+
+Synopsis
+========
+
+.. c:macro:: GPIO_GET_LINEEVENT_IOCTL
+
+``int ioctl(int chip_fd, GPIO_GET_LINEEVENT_IOCTL, struct gpioevent_request *request)``
+
+Arguments
+=========
+
+``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.
+
+Description
+===========
+
+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.
+
+Configuration Rules
+-------------------
+
+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**).
+
+Return Value
+============
+
+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.