1 .. SPDX-License-Identifier: GPL-2.0 2 3 .. _GPIO_GET_LINEEVENT_IOCTL: 4 5 ************************ 6 GPIO_GET_LINEEVENT_IOCTL 7 ************************ 8 9 .. warning:: 10 This ioctl is part of chardev_v1.rst and is obsoleted by 11 gpio-v2-get-line-ioctl.rst. 12 13 Name 14 ==== 15 16 GPIO_GET_LINEEVENT_IOCTL - Request a line with edge detection from the kernel. 17 18 Synopsis 19 ======== 20 21 .. c:macro:: GPIO_GET_LINEEVENT_IOCTL 22 23 ``int ioctl(int chip_fd, GPIO_GET_LINEEVENT_IOCTL, struct gpioevent_request *request)`` 24 25 Arguments 26 ========= 27 28 ``chip_fd`` 29 The file descriptor of the GPIO character device returned by `open()`. 30 31 ``request`` 32 The :c:type:`event_request<gpioevent_request>` specifying the line 33 to request and its configuration. 34 35 Description 36 =========== 37 38 Request a line with edge detection from the kernel. 39 40 On success, the requesting process is granted exclusive access to the line 41 value and may receive events when edges are detected on the line, as 42 described in gpio-lineevent-data-read.rst. 43 44 The state of a line is guaranteed to remain as requested until the returned 45 file descriptor is closed. Once the file descriptor is closed, the state of 46 the line becomes uncontrolled from the userspace perspective, and may revert 47 to its default state. 48 49 Requesting a line already in use is an error (**EBUSY**). 50 51 Requesting edge detection on a line that does not support interrupts is an 52 error (**ENXIO**). 53 54 As with the :ref:`line handle<gpio-get-linehandle-config-support>`, the 55 bias configuration is best effort. 56 57 Closing the ``chip_fd`` has no effect on existing line events. 58 59 Configuration Rules 60 ------------------- 61 62 The following configuration rules apply: 63 64 The line event is requested as an input, so no flags specific to output lines, 65 ``GPIOHANDLE_REQUEST_OUTPUT``, ``GPIOHANDLE_REQUEST_OPEN_DRAIN``, or 66 ``GPIOHANDLE_REQUEST_OPEN_SOURCE``, may be set. 67 68 Only one bias flag, ``GPIOHANDLE_REQUEST_BIAS_xxx``, may be set. 69 If no bias flags are set then the bias configuration is not changed. 70 71 The edge flags, ``GPIOEVENT_REQUEST_RISING_EDGE`` and 72 ``GPIOEVENT_REQUEST_FALLING_EDGE``, may be combined to detect both rising 73 and falling edges. 74 75 Requesting an invalid configuration is an error (**EINVAL**). 76 77 Return Value 78 ============ 79 80 On success 0 and the :c:type:`request.fd<gpioevent_request>` contains the file 81 descriptor for the request. 82 83 On error -1 and the ``errno`` variable is set appropriately. 84 Common error codes are described in error-codes.rst.
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