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1.. SPDX-License-Identifier: GPL-2.02 3.. _GPIO_V2_GET_LINEINFO_WATCH_IOCTL:4 5********************************6GPIO_V2_GET_LINEINFO_WATCH_IOCTL7********************************8 9Name10====11 12GPIO_V2_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its13request state and configuration information.14 15Synopsis16========17 18.. c:macro:: GPIO_V2_GET_LINEINFO_WATCH_IOCTL19 20``int ioctl(int chip_fd, GPIO_V2_GET_LINEINFO_WATCH_IOCTL, struct gpio_v2_line_info *info)``21 22Arguments23=========24 25``chip_fd``26 The file descriptor of the GPIO character device returned by `open()`.27 28``info``29 The :c:type:`line_info<gpio_v2_line_info>` struct to be populated, with30 the ``offset`` set to indicate the line to watch31 32Description33===========34 35Enable watching a line for changes to its request state and configuration36information. Changes to line info include a line being requested, released37or reconfigured.38 39.. note::40 Watching line info is not generally required, and would typically only be41 used by a system monitoring component.42 43 The line info does NOT include the line value.44 The line must be requested using gpio-v2-get-line-ioctl.rst to access45 its value, and the line request can monitor a line for events using46 gpio-v2-line-event-read.rst.47 48By default all lines are unwatched when the GPIO chip is opened.49 50Multiple lines may be watched simultaneously by adding a watch for each.51 52Once a watch is set, any changes to line info will generate events which can be53read from the ``chip_fd`` as described in54gpio-v2-lineinfo-changed-read.rst.55 56Adding a watch to a line that is already watched is an error (**EBUSY**).57 58Watches are specific to the ``chip_fd`` and are independent of watches59on the same GPIO chip opened with a separate call to `open()`.60 61Return Value62============63 64On success 0 and ``info`` is populated with the current line info.65 66On error -1 and the ``errno`` variable is set appropriately.67Common error codes are described in error-codes.rst.68