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#!/usr/bin/python
# Hotplug script for gpsd by Eric S. Raymond, March 2005
# This script is part of the gpsd distribution: see http://gpsd.berlios.de
import sys, os, syslog, glob, socket

def gpsd_control_connect():
    "Acquire a connection to the GPSD control socket."
    try:
        sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM, 0)
        sock.connect("/var/run/gpsd.sock")
        sockfile = sock.makefile()
    except socket.error, msg:
        if sock:
            sock.close()
        sock = None
        sockfile = None
    if not sock:
        syslog.syslog("gpsd is not running or control socket is unreachable")
        return None
    else:
        return sockfile

def wake_up_gpsd(devpath):
    subnodes = glob.glob("/sys" + devpath + "/*")
    subnodes = map(os.path.basename, subnodes)
    subnodes = filter(lambda s: s.startswith("ttyUSB"), subnodes) 
    if len(subnodes) == 0:
        syslog.syslog("no ttyUSB device under " + devpath)
        return
    elif len(subnodes) > 1:
        syslog.syslog("too many ttyUSB devices under " + devpath)
        return
    else:
        tty = "/dev/" + subnodes[0]
        syslog.syslog(tty + " has gone active")

        # Next get a connection to gpsd; start one if not already running
        connect = gpsd_connect()
        if connect:
            syslog.syslog("reached a running gpsd")
        else:
            syslog.syslog("attempting to launch gpsd")
            os.system("gpsd")
            connect = gpsd_control_connect()
        if not connect:
            return

        # We've got a live connection to the gpsd control socket. 
        # No response, because gpsd will lock on to the device
        # if it's really a GPS and ignore it if it's not.
        connect.write("+%s\r\n" % tty)
        connect.close()
        return

def hotplug():
    syslog.openlog('gpsdplug', 0, syslog.LOG_DAEMON)
    syslog.syslog("gpsdplug begins with action: %s" % os.getenv("ACTION"))
    devpath = os.getenv("DEVPATH")
    if not devpath:
        syslog.syslog("No DEVPATH")
    else:
        # First, discover the device
        #syslog.syslog("DEVPATH = %s" % devpath)
        wake_up_gpsd(devpath)

    syslog.syslog("gpsdplug ends")
    syslog.closelog()

if __name__ == '__main__':
    if len(sys.argv) == 1:	# Called as hotplug script
        hotplug()
    else:			# Called by hand for testing
        fp = gpsd_control_connect()
        fp.write(sys.argv[1])
        fp.close()