ogpsd's Start fails with: Known resources are []

[Sascha]

...because ogpsd starts before ousaged:

* NameOwnerChanged: org.freesmartphone.ogpsd
Start() returns error: Known resources are []
* NameOwnerChanged: org.freesmartphone.ousaged
Start() returns no error, but gps device is not powered on

[daniel]

Could you be more verbose in describing this problem?

[Sascha]

The Start and Stop methods of the GPSDevice class need to handle ousaged's errors properly.

The following patch works for my concrete example:

diff --git a/framework/subsystems/ogpsd/gpsdevice.py b/framework/subsystems/ogpsd/gpsdevice.py
index d4ff1f6..05e7e3a 100644
--- a/framework/subsystems/ogpsd/gpsdevice.py
+++ b/framework/subsystems/ogpsd/gpsdevice.py
@@ -215,7 +215,10 @@ class GPSDevice( resource.Resource ):
                 if not self.usageiface:
                     usage = self.bus.get_object( "org.freesmartphone.ousaged", "/org/freesmartphone/Usage", follow_name_owner_changes=True )
                     self.usageiface = dbus.Interface( usage, "org.freesmartphone.Usage" )
-                self.usageiface.RequestResource("GPS", reply_handler=dbus_ok, error_handler=dbus_error )
+                def on_error( error ):
+                    self._users.remove( sender )
+                    dbus_error( dbus.DBusException("RequestResource failed") )
+                self.usageiface.RequestResource("GPS", reply_handler=dbus_ok, error_handler=on_error)
             else:
                 dbus_ok()
         else:

This still requires that all Start and Stop calls/replies/errors are in the expected order, which is not always the case!

A proper fix would be to serialize all Start and Stop calls/replies/errors.

[daniel]

This needs some more thinking about how to handle resource appearance properly.

[daniel]

I have applied the patch now since it already helps in returning a better Error message and removing the sender from the list again.

[stefan]

Patch was applied let's also close this bug.