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author | Kent Gibson <warthog618@gmail.com> | 2024-01-15 03:48:44 +0300 |
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committer | Bartosz Golaszewski <bartosz.golaszewski@linaro.org> | 2024-01-22 12:49:07 +0300 |
commit | 16b2bb7fe5e4a0757608e844902fdf05617f51f8 (patch) | |
tree | faeccf341e6dbca0f9c4b19cd618a48cf8df2b0a /Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst | |
parent | e10b641753837e267462b64f8cb395ab1e625027 (diff) | |
download | linux-16b2bb7fe5e4a0757608e844902fdf05617f51f8.tar.xz |
Documentation: gpio: add chardev v1 userspace API documentation
Add documentation for v1 of the GPIO character device userspace API
to the obsolete section of both the admin-guide and userspace-api
books.
Signed-off-by: Kent Gibson <warthog618@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Diffstat (limited to 'Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst')
-rw-r--r-- | Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst b/Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst new file mode 100644 index 000000000000..f5c92b69a496 --- /dev/null +++ b/Documentation/userspace-api/gpio/gpio-get-lineinfo-watch-ioctl.rst @@ -0,0 +1,74 @@ +.. SPDX-License-Identifier: GPL-2.0 + +.. _GPIO_GET_LINEINFO_WATCH_IOCTL: + +***************************** +GPIO_GET_LINEINFO_WATCH_IOCTL +***************************** + +.. warning:: + This ioctl is part of chardev_v1.rst and is obsoleted by + gpio-v2-get-lineinfo-watch-ioctl.rst. + +Name +==== + +GPIO_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its +request state and configuration information. + +Synopsis +======== + +.. c:macro:: GPIO_GET_LINEINFO_WATCH_IOCTL + +``int ioctl(int chip_fd, GPIO_GET_LINEINFO_WATCH_IOCTL, struct gpioline_info *info)`` + +Arguments +========= + +``chip_fd`` + The file descriptor of the GPIO character device returned by `open()`. + +``info`` + The :c:type:`line_info<gpioline_info>` struct to be populated, with + the ``offset`` set to indicate the line to watch + +Description +=========== + +Enable watching a line for changes to its request state and configuration +information. Changes to line info include a line being requested, released +or reconfigured. + +.. note:: + Watching line info is not generally required, and would typically only be + used by a system monitoring component. + + The line info does NOT include the line value. + + The line must be requested using gpio-get-linehandle-ioctl.rst or + gpio-get-lineevent-ioctl.rst to access its value, and the line event can + monitor a line for events using gpio-lineevent-data-read.rst. + +By default all lines are unwatched when the GPIO chip is opened. + +Multiple lines may be watched simultaneously by adding a watch for each. + +Once a watch is set, any changes to line info will generate events which can be +read from the ``chip_fd`` as described in +gpio-lineinfo-changed-read.rst. + +Adding a watch to a line that is already watched is an error (**EBUSY**). + +Watches are specific to the ``chip_fd`` and are independent of watches +on the same GPIO chip opened with a separate call to `open()`. + +First added in 5.7. + +Return Value +============ + +On success 0 and ``info`` is populated with the current line info. + +On error -1 and the ``errno`` variable is set appropriately. +Common error codes are described in error-codes.rst. |