Philippe Gerum authored Feb 04, 2019 and Jan Kiszka committed Feb 04, 2019

In timestamping mode, read() returns the timestamp of the latest event
receipt on the pin based on CLOCK_MONOTONIC, along with the pin
state. This is an optional pin readout mode controlled by the
GPIO_RTIOC_TS request, e.g.:

struct rtdm_gpio_readout rdo;
int ret, on, val;

on = 1;
ret = ioctl(pinfd, GPIO_RTIOC_TS, &on);
ret = read(pinfd, &rdo, sizeof(rdo));
/* pin state changed to rdo.value at time rdo.timestamp */

on = 0;
ret = ioctl(pinfd, GPIO_RTIOC_TS, &on);
ret = read(pinfd, &val, sizeof(val));
/* pin state changed to value (time of change unspecified) */

By default, timestamping mode is disabled, which corresponds to the
original behavior.

Signed-off-by: Philippe Gerum <rpm@xenomai.org>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>