| GPIOPPS(4) | Device Drivers Manual | GPIOPPS(4) | 
gpiopps —
gpiopps* at gpio? offset 0 mask 0x1 flag 0x0
gpiopps driver provides a 1PPS handler using the
  PPSAPI on one or two GPIO pins.
The base pin number is specified in the kernel configuration file with the offset locator. The mask should have 1 or 2 bits set, indicating which pins offset from the base pin should be used (0 .. 31). Pin configurations are discussed below.
The flag locator modifies the pin configuraiton:
0x010x02gpiopps will use double-edge
      triggering when only a single pin is specified and the underlying GPIO
      hardware supports it. This flag disables the use of double-edge
      triggering.If a single pin is specified, gpiopps uses
    double-edge triggering to support ASSERT and CLEAR PPS signals. If the
    underlying GPIO hardware does not support double-edge triggering, or if this
    feature is diabled in the flag locator, then only
    ASSERT will be signaled on the specified edge.
If two pins are specified, the first pin is used to trigger the ASSERT signal and the second pin is used to trigger the CLEAR signal. The ASSERT pin's trigger edge is specified by by the flag locator, and the CLEAR pin triggers on the opposite edge. This allows ASSERT and CLEAR signals to be triggered even if the underlying GPIO hardware does not support double-edge triggering. In this scenario, both GPIO pins would be connected in parallel to the device sending the 1PPS signals.
The offset, mask, and
    flag locators can also be specified when
    gpiopps is attached at runtime using the
    GPIOATTACH
    ioctl(2) on the
    gpio(4) device.
gpiopps driver first appeared in
  NetBSD 9.0.
gpiopps driver was written by Brad
  Spencer
  <brad@anduin.eldar.org>.
| May 11, 2018 | NetBSD 9.4 |