tty line discipline driver advice sought, to do a 1-byte header and 2-byte CRC checksum on GSM data

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]


hello darlings, please cc me because i am not subscribed to these lists.  ta.
i am cross-posting because, whilst this is for a phone device, it's
actually a request for help on tty line discipline driver writing.

you may have heard of quite a bit of fuss over linux mobile phones,
recently, with the introduction of the Neo1973 from and
the greenphone from - well, there are a few more
devices around which are tantalisingly close to being useable: the
htc universal, the htc sable (ipaq hw6915) and also the h6300 series i
understand is _already_ actually useable - it even has a gsm management
daemon (

some of you may have also seen this:

that's the background.

my question is this: having looked at the htc sable's K700 gsm module,
which talks some weird proprietary but easily-reverse-engineered protocol:

and having read harald's email, and basically gone 'cool!', and, having
then looked up 'tty line discipline' on google (_before_ writing
this...) and gone 'errr...' i was wondering:

could someone kindly advise me how to write a tty line discipline

i need to add one byte to the front (0x2) then a 2-byte length field,
then send the data that's written, then a 2-byte CRC-16 checksum, and, also,
on a read, to check that the first byte is a 0x2, then read the length
field, then that many bytes, and confirm the 2-byte CRC-16 checksum of
the data just read.

i've never encountered tty line discipline's before.  which one is the
best example that i should start with to cut/paste?  has anyone else
done this sort of thing before, such that i can start with their code
and do a minimum amount of work to get this done - quickly?  can anyone
point me at userspace test example source code?

etc. etc.

... alternatively, i just... don't do this at all - i leave it to
userspace, which would be a hell of a lot easier, but would make
applications a pain, because they would need to use a library instead of
just opening /dev/ttySN just like any other phone app, to transfer AT

your kind assistance to further the free software community's standing
by successfully owning their own mobile phone is greatfully appreciated.


-- - mad free software computer person, visionary and poet.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at
Please read the FAQ at

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux