Handle network-initiated ussd requests.

This adds the methods on the D-bus interface to allow the
client to handle USSD requests from the network, according to 22.090.
Unfortunately this document is not clear on every point and some
details can't be implemented.  This includes reporting unsupported
request to the network, unsupported language, ME busy etc, because
there isn't an AT command for that.

1 files changed, 64 insertions, 0 deletions

diff --git a/doc/ussd-api.txt b/doc/ussd-api.txt
new file mode 100644
index 00000000..83d3cee7
--- /dev/null
+++ b/doc/ussd-api.txt
@@ -0,0 +1,64 @@
+SupplementaryServices hierarchy
+==========================
+
+Service		org.ofono
+Interface	org.ofono.SupplementaryServices
+Object path	[variable prefix]/{modem0,modem1,...}
+
+Methods		string, variant Initiate(string command)
+
+			Sends a USSD command string to the network
+			initiating a session.  When the request is handled
+			by the appropriate node of the network, the
+			method returns the response or an appropriate
+			error.  The network may be awaiting further response
+			from the ME after returning from this method and no
+			new command can be initiated until this one is
+			cancelled or ended.
+
+		void Respond(string reply)
+
+			Send a response to the network either when
+			it is awaiting further input after Initiate()
+			was called or after a network-initiated request.
+
+		void Cancel()
+
+			Cancel an ongoing USSD session, mobile- or
+			network-initiated.
+
+		dict GetProperties()
+
+			Returns Supplementary Services related properties. See
+			the properties section for available properties.
+
+Signals		NotificationReceived(string message)
+
+			Signal is emitted on a network-initiated USSD
+			request for which no response is needed.
+
+		RequestReceived(string message)
+
+			Signal is emitted on a network-initiated USSD
+			request for which a response must be sent using
+			the Respond method unless it is cancelled or
+			the request is not supported.
+
+		PropertyChanged(string property, variant value)
+
+			Signal is emitted whenever a property has changed.
+			The new value is passed as the signal argument.
+
+Properties	string USSDState [readonly]
+
+			Reflects the state of current USSD session.  The
+			values have the following meanings:
+
+			"idle"			 No active USSD session.
+			"active"		 A session is active between the
+						 network and the ME, the ME is
+						 waiting for a reply from the
+						 network.
+			"awaiting-user-response" The network is waiting for the
+						 user's response, client must
+						 call Respond().