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doc:appunti:hardware:eeepc_navit [2011/04/22 11:30] – [Installing the GPS daemon] niccolodoc:appunti:hardware:eeepc_navit [2011/04/22 13:00] (current) – [Installing the GPS daemon] niccolo
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 </code> </code>
  
-===== Installing the GPS daemon =====+===== Installing gpsd, the GPS daemon =====
  
 This was tested on Debian Squeeze 6.0. This was tested on Debian Squeeze 6.0.
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 </file> </file>
  
-This will start **''gpsd''** at bootstrap, it will wait for the GPS to be connected to the USB port. When the USB is connected the udev rule will not start ''gpsd'' by itself, if it is not already running.+This will start **''gpsd''** at bootstrap, it will wait for the GPS to be connected to the USB port. **Note:** when the USB is connected, ''udev'' will not start ''gpsd'' if it is not already running (i.e. when ''START_DAEMON="false"'').
  
 **''udev''** will handle the automatic connection of the GPS via USB, there is a script **''/lib/udev/rules.d/60-gpsd.rules''** in Debian Squeeze which includes the **[[gps_logger_i_blue_747|i-Blue 747 USB GPS logger]]**. **''udev''** will handle the automatic connection of the GPS via USB, there is a script **''/lib/udev/rules.d/60-gpsd.rules''** in Debian Squeeze which includes the **[[gps_logger_i_blue_747|i-Blue 747 USB GPS logger]]**.
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 $GPGGA,112814.000,4353.5310,N,01106.0969,E,0,3,,102.4,M,47.6,M,,*4B $GPGGA,112814.000,4353.5310,N,01106.0969,E,0,3,,102.4,M,47.6,M,,*4B
 </code> </code>
-==== Problems to be solved with gpsd ====+==== Problem #1: plug/unplug ====
  
-We want to be able to plug/unplug the GPS device in the USB port and gpsd should work seamless, but there are two problems:+When a gps client opens a connection with gpsd, it starts receiving data. If GPS device is unplugged and plugged again, the connection does not restart automatically. A workaround is to execute **''gpspipe -r n1''** into another terminal to force device re-opening.
  
-  - **Permissions**: if gpsd starts with no GPS is connected, it switches to group **nobody**. When a GPS is connected, udev add the /dev/ttyUSB device as **root:dialout** and /lib/udev/gpsd.hotplug assigns mode **0660**. In this scenario gpsd cannot read the device. +I hacked **''/lib/udev/gpsd.hotplug''**, adding the execution of that command when the device is re-added. This is the patch:
-  - **GPS unplug/plug**: when a gps client opens a connection with gpsd, it starts receiving data. If GPS device is unplugged and plugged again, the connection does not restart automatically. A workaround is to execute **''gpspipe -r n1''** to force device re-opening. +
- +
-A workaround at the first problem is to let /etc/init.d/udev create a node for /dev/ttyS0 at boot time, even if no devices are present. Per default gpsd will read the group of this device and switches to that group.+
  
 <code> <code>
-mknod -m 0660 /lib/udev/devices c 4 64 +--- gpsd.hotplug.orig   2010-06-02 23:03:02.000000000 +0200 
-chown root:dialout /lib/udev/devices++++ gpsd.hotplug        2011-04-22 12:44:32.000000000 +0200 
 +@@ -114,6 +114,9 @@ 
 +                 hotplug(os.getenv("ACTION"), os.getenv("DEVPATH")) 
 +             else:                      # Called by hand for testing 
 +                 gpsd_control(sys.argv[1], sys.argv[2]) 
 ++                if sys.argv[1] == 'add': 
 ++                    # Wake-up all the listening clients. 
 ++                    os.system("/usr/bin/gpspipe -r -n1 &") 
 +         except: 
 +             (exc_type, exc_value, exc_traceback) = sys.exc_info() 
 +             syslog.syslog("gpsd.hotplug: exception %s yields %s" % (exc_type, exc_value))
 </code> </code>
  
-For the second problem I hacked **''/lib/udev/gpsd.hotplug''**, adding the execution of a script when the device is re-added:+==== Problem #2: permissions ====
  
-<code python> +With Debian Lenny there is a **permission problem**: if gpsd starts with no GPS connected, it switches to group **nobody**. When a GPS is connected, udev add the ''/dev/ttyUSB'' device as **root:dialout** and ''/lib/udev/gpsd.hotplug'' assigns mode **0660**. In this scenario gpsd cannot read the device.
-    if action == 'add': +
-        # Force the group-read & group-write bits on, so gpsd will still be +
-        # able to use this device after dropping root privileges. +
-        os.chmod(argument, stat.S_IMODE(os.stat(argument)[stat.ST_MODE])|0660) +
-        connect.sendall("+%s\r\n" % argument) +
-        connect.recv(12) +
-        os.system('/usr/local/bin/gps-reopen') +
-</code>+
  
-The script is simple this:+A workaround is to create a node for ''/dev/ttyS0'' owned by group dialout at boot time, even if no such device is present. Per default ''gpsd'' will read the group of this device and switches to that group.
  
-<code bash> +It should be possibile to create such a static device into **''/lib/udev/devices/''**, udev will copy it under ''/dev/'' at boot time: 
-#!/bin/sh + 
-/bin/echo /usr/bin/gpspipe -r -n1 | /usr/bin/at now+<code> 
 +mknod -m 0660 /lib/udev/devices/ttyS0 c 4 64 
 +chown root:dialout /lib/udev/devices/ttyS0
 </code> </code>
- 
-Don't ask me why I need running gpspipe it via **at**, I suspect there is the need of a controlling terminal, etc... 
  
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doc/appunti/hardware/eeepc_navit.1303464630.txt.gz · Last modified: 2011/04/22 11:30 by niccolo