LINUX GPIO DAEMON (GPIOD)

Daemon to monitor gpio via sysfs or uapi interface and send them over network or execute user defined hooks with desired arguments.

Requirements

libconfuse (https://github.com/martinh/libconfuse.git)

Explanatory note

Concept

gpiod supports both uapi and sysfs interface and currently (although this is not recommended) it can be used both at the same time. Triggers can be set to rising edge, falling edge, both or be polled via configured interval.

On being triggered an event is dispatched to all connected clients.

gpiod fully acts as a daemon, through it needs privileges to be launched as gpio’s are not considered user-space.

Installation

Compiling

For version that supports both sysfs and uapi simply invoke:

$ make

For sysfs only version provide flag:

$ make WITHOUT_GPIOD_UAPI=1

Cross-Compiling

$ make CROSS_COMPILE=${TARGET_CROSS}-
# for example:
$ make CROSS_COMPILE=arm-none-linux-gnueabi-

Installing

$ make DESTDIR= prefix= install

Both DESTDIR and prefix should be used when installing to an extern rootfs.

By default /etc/gpio.d and /etc/gpiod.conf are not created - you can find different examples in etc directory of repository.

Tests

Some sanity tests are provided in tests. bats (https://github.com/sstephenson/bats) is additionally required to perform tests.

Running

Following options can be passed:

-v, --version              prints version and exits
-V, --verbose              be more verbose
-l, --log-level            set log level[default=LOG_INFO]
-n                         don't fork off as daemon
-k, --kill                 kill old daemon instance in case if present
-H, --hup                  send daemon signal to reload configuration
-p, --pid                  path to pid file[default=/var/run/gpiod.pid]
-c, --config=FILE          configuration file[default=/etc/gpiod/gpiod.conf]
-d, --tabdir=DIR           tabs location directory[default=/etc/gpiod.d/]
-h, --help                 prints this message

Configuration file

# (optional) listen on specific address, can be overriden by cmd args [default=127.0.0.1]
listen = 127.0.0.1
# (optional) listen on port, can be overriden by cmd args [default=1500]
port = 1500
# (optional) poll interval in msec, can be overriden by cmd args [default = 50]
poll = 50

gpio {
  # facility to use for this gpio sysfs or uapi [default = uapi]
  facility = uapi

  # (optional) calculated system gpio offset [nodefault]
  system = 256

  # (optional) gpiochip name [nodefault]
  gpiochip = gpiochip0

  # (optional) local offset in gpiochip, can be negative [nodefault]
  offset = 0

  # (optional) local mapping [default=system]
  local = 0

  # label for passing via libpack i.e. WD0, WD1, ..., WDN
  label = WD0

  # rising, falling, both, polled [default=both]
  edge = both
}

Hook tabs

gpiod supports launching user defined executables based on configured trigger files placed under /etc/gpio.d or specified by –tabdir,-d argument.

Tab files should be in form of :

[LABEL] [MODIFIERS]         [PATH]       [ARGS]
WD0     EDGE_RISING         /tmp/test.sh -n --version -v 23 -s test $@ $% $&

Where LABEL is pin label defined in config file i.e. label =, MODIFIERS one of EDGE_RISING, EDGE_FALLING, EDGE_BOTH and (optional) NO_LOOP, ONESHOT flags.

NO_LOOP prevents launching before previous launch has finished and ONESHOT to launch hook only once per daemon lifetime.

see etc/gpio.d/testtab example.