1.. SPDX-License-Identifier: GPL-2.0 2 3======================================== 4GPIO Character Device Userspace API (v1) 5======================================== 6 7.. warning:: 8 This API is obsoleted by chardev.rst (v2). 9 10 New developments should use the v2 API, and existing developments are 11 encouraged to migrate as soon as possible, as this API will be removed 12 in the future. The v2 API is a functional superset of the v1 API so any 13 v1 call can be directly translated to a v2 equivalent. 14 15 This interface will continue to be maintained for the migration period, 16 but new features will only be added to the new API. 17 18First added in 4.8. 19 20The API is based around three major objects, the :ref:`gpio-v1-chip`, the 21:ref:`gpio-v1-line-handle`, and the :ref:`gpio-v1-line-event`. 22 23Where "line event" is used in this document it refers to the request that can 24monitor a line for edge events, not the edge events themselves. 25 26.. _gpio-v1-chip: 27 28Chip 29==== 30 31The Chip represents a single GPIO chip and is exposed to userspace using device 32files of the form ``/dev/gpiochipX``. 33 34Each chip supports a number of GPIO lines, 35:c:type:`chip.lines<gpiochip_info>`. Lines on the chip are identified by an 36``offset`` in the range from 0 to ``chip.lines - 1``, i.e. `[0,chip.lines)`. 37 38Lines are requested from the chip using either gpio-get-linehandle-ioctl.rst 39and the resulting line handle is used to access the GPIO chip's lines, or 40gpio-get-lineevent-ioctl.rst and the resulting line event is used to monitor 41a GPIO line for edge events. 42 43Within this documentation, the file descriptor returned by calling `open()` 44on the GPIO device file is referred to as ``chip_fd``. 45 46Operations 47---------- 48 49The following operations may be performed on the chip: 50 51.. toctree:: 52 :titlesonly: 53 54 Get Line Handle <gpio-get-linehandle-ioctl> 55 Get Line Event <gpio-get-lineevent-ioctl> 56 Get Chip Info <gpio-get-chipinfo-ioctl> 57 Get Line Info <gpio-get-lineinfo-ioctl> 58 Watch Line Info <gpio-get-lineinfo-watch-ioctl> 59 Unwatch Line Info <gpio-get-lineinfo-unwatch-ioctl> 60 Read Line Info Changed Events <gpio-lineinfo-changed-read> 61 62.. _gpio-v1-line-handle: 63 64Line Handle 65=========== 66 67Line handles are created by gpio-get-linehandle-ioctl.rst and provide 68access to a set of requested lines. The line handle is exposed to userspace 69via the anonymous file descriptor returned in 70:c:type:`request.fd<gpiohandle_request>` by gpio-get-linehandle-ioctl.rst. 71 72Within this documentation, the line handle file descriptor is referred to 73as ``handle_fd``. 74 75Operations 76---------- 77 78The following operations may be performed on the line handle: 79 80.. toctree:: 81 :titlesonly: 82 83 Get Line Values <gpio-handle-get-line-values-ioctl> 84 Set Line Values <gpio-handle-set-line-values-ioctl> 85 Reconfigure Lines <gpio-handle-set-config-ioctl> 86 87.. _gpio-v1-line-event: 88 89Line Event 90========== 91 92Line events are created by gpio-get-lineevent-ioctl.rst and provide 93access to a requested line. The line event is exposed to userspace 94via the anonymous file descriptor returned in 95:c:type:`request.fd<gpioevent_request>` by gpio-get-lineevent-ioctl.rst. 96 97Within this documentation, the line event file descriptor is referred to 98as ``event_fd``. 99 100Operations 101---------- 102 103The following operations may be performed on the line event: 104 105.. toctree:: 106 :titlesonly: 107 108 Get Line Value <gpio-handle-get-line-values-ioctl> 109 Read Line Edge Events <gpio-lineevent-data-read> 110 111Types 112===== 113 114This section contains the structs that are referenced by the ABI v1. 115 116The :c:type:`struct gpiochip_info<gpiochip_info>` is common to ABI v1 and v2. 117 118.. kernel-doc:: include/uapi/linux/gpio.h 119 :identifiers: 120 gpioevent_data 121 gpioevent_request 122 gpiohandle_config 123 gpiohandle_data 124 gpiohandle_request 125 gpioline_info 126 gpioline_info_changed 127 128.. toctree:: 129 :hidden: 130 131 error-codes 132