1 .. SPDX-License-Identifier: GPL-2.0 2 3 .. _GPIO_GET_LINEINFO_WATCH_IOCTL: 4 5 ***************************** 6 GPIO_GET_LINEINFO_WATCH_IOCTL 7 ***************************** 8 9 .. warning:: 10 This ioctl is part of chardev_v1.rst and is obsoleted by 11 gpio-v2-get-lineinfo-watch-ioctl.rst. 12 13 Name 14 ==== 15 16 GPIO_GET_LINEINFO_WATCH_IOCTL - Enable watching a line for changes to its 17 request state and configuration information. 18 19 Synopsis 20 ======== 21 22 .. c:macro:: GPIO_GET_LINEINFO_WATCH_IOCTL 23 24 ``int ioctl(int chip_fd, GPIO_GET_LINEINFO_WATCH_IOCTL, struct gpioline_info *info)`` 25 26 Arguments 27 ========= 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, with 34 the ``offset`` set to indicate the line to watch 35 36 Description 37 =========== 38 39 Enable watching a line for changes to its request state and configuration 40 information. Changes to line info include a line being requested, released 41 or reconfigured. 42 43 .. note:: 44 Watching line info is not generally required, and would typically only be 45 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 or 50 gpio-get-lineevent-ioctl.rst to access its value, and the line event can 51 monitor a line for events using gpio-lineevent-data-read.rst. 52 53 By default all lines are unwatched when the GPIO chip is opened. 54 55 Multiple lines may be watched simultaneously by adding a watch for each. 56 57 Once a watch is set, any changes to line info will generate events which can be 58 read from the ``chip_fd`` as described in 59 gpio-lineinfo-changed-read.rst. 60 61 Adding a watch to a line that is already watched is an error (**EBUSY**). 62 63 Watches are specific to the ``chip_fd`` and are independent of watches 64 on the same GPIO chip opened with a separate call to `open()`. 65 66 First added in 5.7. 67 68 Return Value 69 ============ 70 71 On success 0 and ``info`` is populated with the current line info. 72 73 On error -1 and the ``errno`` variable is set appropriately. 74 Common error codes are described in error-codes.rst.
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