Cinterion radio bands

[Giacinto Cifelli]

Hey Aleksander,


On Mon, May 18, 2020 at 1:11 PM Aleksander Morgado
<aleksander at aleksander.es> wrote:
>
> Hey,
>
> > > > > > > > I am trying to update the code for the Radio/Bands of Cinterion
> > > > > > > > Today in the code there is a parser for this format (only for the test part):
> > > > > > > > AT^SCFG=?
> > > > > > > >         ^SCFG: "Radio/Band",("1-479","0-1")
> > > > > > > >
> > > > > > > >  the PLS62 reports:
> > > > > > > > under GSM charset:
> > > > > > > > AT^SCFG=?
> > > > > > > >      ^SCFG: "Radio/Band/2G",("0x00000004"-"0x00000074")
> > > > > > > >      ^SCFG: "Radio/Band/3G",("0x00000001"-"0x0004019B")
> > > > > > > >      ^SCFG: "Radio/Band/4G",("0x00000001"-"0x080E08DF")
> > > > > > > > and under UCS2 charset:
> > > > > > > >    AT^SCFG=?
> > > > > > > >      ^SCFG: "Radio/Band/2G",("0030007800300030003000300030003000300034"-"0030007800300030003000300030003000370034")
> > > > > > > >      ^SCFG: "Radio/Band/3G",("0030007800300030003000300030003000300031"-"0030007800300030003000340030003100390042")
> > > > > > > >      ^SCFG: "Radio/Band/4G",("0030007800300030003000300030003000300031"-"0030007800300038003000450030003800440046")
> > > > > > >
> > > > > > > > To determine the charset, I use some heuristics on string length and
> > > > > > > > prefix (0x aka 00300078). Note also that a model returns lowercase
> > > > > > > > hexa while another uppercase...
> > > > > > >
> > > > > > > Isn't mm_broadband_modem_get_current_charset () not returning the
> > > > > > > correct thing? I would definitely avoid doing heuristics to detect
> > > > > > > charset if possible.
> > > > > >
> > > > > Is there not a CSCS=? check during initialization, plus a CSCS=X set
> > > > > command after that? I believe that ModemManager tries to set the
> > > > > "best" charset of the ones available. Do you have a full debug log to
> > > > > check how that is happening?
> > > > >
> > > > > > The only time it is called is after setting it, and it looks like it
> > > > > > requires a dbus input, and therefore can only happen after the modem
> > > > > > is detected.
> > > > >
> > > > > No no, there is no charset setting based on DBus calls. It's done during init.
> > > > >
> > > > > > Unfortunately the call above happens during the modem detection phase.
> > > > > >
> > > > > > one fix could be sending the line
> > > > > >     AT+CSCS="GSM"
> > > > > > in the initialization, along with other test commands like AT*CNTI=2?
> > > > > >
> > > >
> > > > I have checked the code, and the charset detection&set is part of the
> > > > enable state machine, while the radio/band detection is part of the
> > > > modem discovery state machine in :src/mm-iface-modem.c:
> > > >
> > > > typedef enum {
> > > >     ...
> > > >     ENABLING_STEP_SUPPORTED_CHARSETS,
> > > >     ENABLING_STEP_CHARSET,
> > > >     ...
> > > > } EnablingStep;
> > > >
> > > > typedef enum {
> > > >     ...
> > > >    INITIALIZATION_STEP_SUPPORTED_BANDS,
> > > >     ...
> > > >    INITIALIZATION_STEP_CURRENT_BANDS,
> > > >     ...
> > > > } InitializationStep;
> > > >
> > > > It is possible that other initialization steps require the right
> > > > charset. Wouldn't be good to move the charset settings among these
> > > > steps?
> > > > After all setting the charset is part of setting up the communication
> > > > channel, a bit like the baudrate and similar parameters.
> > > >
> > >
> > > That makes sense I think, yes. Would you like to send a patch for that?
> > >
> >
> > Yes, however I fear some regressions. For example, things work in the
> > current Cinterion supported/current bands because the charset is
> > 'unknown'.
> > I would propose to split the supported & detection during the initial
> > phase, and the actual setting of the charset where it is.
> >
>
> I'm not really sure about that; you actually convinced me when you
> said that initializing charset is a bit like initializing the serial
> channel :D
> Why do you say that things work because the channel is unknown?
>

I have moved the two procedures (need to clean the code before
submitting) to the init phase, and seems to work well, so I will
submit the change.

My point above is the following. During the init phase, all
conversions are handled as follow:
            if (charset != MM_MODEM_CHARSET_UNKNOWN)
                maxbandstr = mm_charset_take_and_convert_to_utf8
(maxbandstr, charset);

since the charset was not initialized so far, we are guaranteed that
the if() above fails, and therefore whatever follows has been tested
on untranslated strings.
What if now the string is different?
I can and will test for the modems I have, but cannot guarantee for
other plugins.

Regards,
Giacinto