RE: Support text mode sms send and receive

-----Original Message----- From: Denis Kenzior [mailto:denkenz@gmail.com] Sent: 2010年8月25日 2:52 To: ofono(a)ofono.org Cc: Su, Yong Subject: Re: Support text mode sms send and receive Hi Su Yong, On 08/23/2010 04:11 AM, Su, Yong wrote: > Hi, all: > > Our project used ZTE EVDO modem. But this modem only supports sending > and receiving sms with text mode. > I have modify oFono gatchat code to support this. But it conflicted > with original gatchat architecture. > Does oFono plan to support text mode sms send&receive? > > So oFono explicitly does not want to support text mode. There are many reasons for this, but let me list the most important ones: - oFono core deals with raw PDUs. That is the universal standard between AT modems and binary protocol based modems. This PDU format is well understood, simple to decode / generate and the utilities in oFono cover just about every use case. If you decide to do text mode, then you will have to: - Solve the AT command parser issues - Collect all the SMS pieces - Encode them back into a PDU At which point oFono will take the PDU and decode it back to something that can be used. This is a MAJOR waste of CPU power and resources. Changing the driver API here is highly unlikely. This is not to mention other interaction problems which depend on PDU mode being available (e.g. Sim Toolkit Send SMS, SMS-PP Data Download, etc) - Text mode depends on setting or otherwise messing with +CSCS. Most AT command based modems do not handle this very gracefully. Most other drivers will expect the IRA character set and you will start random errors. There's of course a chance that your modem can handle this properly (perhaps you have a decent multiplexer implementation in which CSCS affects a single channel only, _and_ you wall-off the SMS part on that multiplexer channel), but my experience with GSM modems leaves me extremely skeptical. - The AT parser for this is essentially a disaster area. Every modem has its own quirks for text mode. It is something that a human being can understand and work around, but for a library like GAtChat the complexity will be huge. Even if you make it work on this particular modem, it _has_ to work on other modems as well. Please note that there are no modern GSM telephony stacks that use text mode SMS for exactly those reasons. So the question is, can you ask your modem manufacturer to provide firmware that supports PDU mode? Regards, -Denis