Lines Matching +full:read +full:- +full:to +full:- +full:read

1 .. SPDX-License-Identifier: GPL-2.0
11     gpio-v2-line-event-read.rst.
16 GPIO_LINEEVENT_DATA_READ - Read edge detection events from a line event.
21 ``int read(int event_fd, void *buf, size_t count)``
28     :c:type:`request.fd<gpioevent_request>` by gpio-get-lineevent-ioctl.rst.
31     The buffer to contain the :c:type:`events<gpioevent_data>`.
40 Read edge detection events for a line from a line event.
47 Edges are defined in terms of changes to the logical line value, so an inactive
48 to active transition is a rising edge.  If ``GPIOHANDLE_REQUEST_ACTIVE_LOW`` is
50 ``GPIOEVENT_REQUEST_RISING_EDGE`` then corresponds to a falling physical edge.
52 The kernel captures and timestamps edge events as close as possible to their
53 occurrence and stores them in a buffer from where they can be read by
54 userspace at its convenience using `read()`.
59 as to which clock source is used, it must be determined from either the kernel
62 Events read from the buffer are always in the same order that they were
67 The buffer may overflow if bursts of events occur quicker than they are read
71 To minimize the number of calls required to copy events from the kernel to
72 userspace, `read()` supports copying multiple events. The number of events
76 The `read()` will block if no event is available and the ``event_fd`` has not
85 On success the number of bytes read, which will be a multiple of the size of
88 On error -1 and the ``errno`` variable is set appropriately.
89 Common error codes are described in error-codes.rst.