RE: Clarification on USSD support in ofono

[Marcel Holtmann <marcel@holtmann.org>]

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Hi Jeevaka,

> >   Currently, oFono expects the USSD string in UTF-8. ofono(Atom driver
> > - AT or ISI) converts the UTF-8 string to GSM 7-bit default alphabet 
> > and sends it to the network. In this way, we will always send the data
> 
> > coding scheme as GSM 7-bit default alphabet or whatever the character 
> > set modem is configured. Why are we not sending the USSD string with 
> > DCS(Data coding scheme) as is to the network? There are USIM 
> > conformance test cases which expects the DCS(Data coding scheme) and 
> > USSD string sent as it is to the network. Also, as per the 3GPP TS 
> > 24.090, DCS and USSD string are sent as part of UnstructuredSS-Request
> 
> > to the network and MT is not expected to interpret the string.
> > But ,here oFono doesn't have the interface to accept DCS(Data coding
> > scheme) and also it expects the USSD string to be in UTF-8. 
> 
> > the one main design goal behind oFono's D-Bus APIs is to make them
> useful for users. This means that the main input data type are strings
> and they are UTF-8.
> 
> > If you need magic binary APIs that are only used by specific
> application or even purely for conformance testing, then you need to
> propose an interface for these. By default we will not make application
> > to any kind of conversation.
> 
> > Every single nasty conversion that has to be done by every single
> application using such an interface is wrong. Complexity belongs into
> oFono and not the application. The idea of just pushing complex 
> > tasks up into the application so that oFono doesn't have to deal with
> it is a really bad idea. Remember that one main goal of oFono is to make
> the usage of standard telephony functionality as easy as
> > possible when you are developing telephony applications.
> 
> 
> I'm not proposing any changes to the dbus interface and I completely
> understand that its a very bad idea to push the conversions to the
> application side. USAT conformance specification expects that the
> information sent by the application toolkit to be sent as it is to the
> network. Conformance test setup is such that if the data received at the
> network doesn't match with the data sent by the application toolkit then
> the conformance test case is considered to be a failure case.
> 
> When a Send USSD proactive command is received, STK atom sends an
> internal request to the USSD atom to send the string along with the DCS
> supplied. So, for sending the USSD string and dcs received from the
> proactive command, support needs to be added to the USSD driver
> interface. 

you have me confused now. Are you talking about the D-Bus based API
towards applications or the SIM Toolkit support?

SIM Toolkit is something totally different. Even for SMS we just deal
with raw PDUs there. While the user side applications over D-Bus will
never get access to the raw PDUs.

Regards

Marcel