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1.. SPDX-License-Identifier: GPL-2.02 3.. _GPIO_GET_LINEINFO_WATCH_IOCTL:4 5*****************************6GPIO_GET_LINEINFO_WATCH_IOCTL7*****************************8 9.. warning::10 This ioctl is part of chardev_v1.rst and is obsoleted by11 gpio-v2-get-lineinfo-watch-ioctl.rst.12 13Name14====15 16GPIO_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its17request state and configuration information.18 19Synopsis20========21 22.. c:macro:: GPIO_GET_LINEINFO_WATCH_IOCTL23 24``int ioctl(int chip_fd, GPIO_GET_LINEINFO_WATCH_IOCTL, struct gpioline_info *info)``25 26Arguments27=========28 29``chip_fd``30 The file descriptor of the GPIO character device returned by `open()`.31 32``info``33 The :c:type:`line_info<gpioline_info>` struct to be populated, with34 the ``offset`` set to indicate the line to watch35 36Description37===========38 39Enable watching a line for changes to its request state and configuration40information. Changes to line info include a line being requested, released41or reconfigured.42 43.. note::44 Watching line info is not generally required, and would typically only be45 used by a system monitoring component.46 47 The line info does NOT include the line value.48 49 The line must be requested using gpio-get-linehandle-ioctl.rst or50 gpio-get-lineevent-ioctl.rst to access its value, and the line event can51 monitor a line for events using gpio-lineevent-data-read.rst.52 53By default all lines are unwatched when the GPIO chip is opened.54 55Multiple lines may be watched simultaneously by adding a watch for each.56 57Once a watch is set, any changes to line info will generate events which can be58read from the ``chip_fd`` as described in59gpio-lineinfo-changed-read.rst.60 61Adding a watch to a line that is already watched is an error (**EBUSY**).62 63Watches are specific to the ``chip_fd`` and are independent of watches64on the same GPIO chip opened with a separate call to `open()`.65 66First added in 5.7.67 68Return Value69============70 71On success 0 and ``info`` is populated with the current line info.72 73On error -1 and the ``errno`` variable is set appropriately.74Common error codes are described in error-codes.rst.75