[PATCH libosmocore 0/8] Cell Broadcast (SMSCB) MS support

Alex Badea vamposdecampos at gmail.com
Mon Jan 7 13:22:22 UTC 2013


On Sun, Jan 6, 2013 at 5:10 PM, Sylvain Munaut <246tnt at gmail.com> wrote:
>> i) if we want to hook it into LAPDm, it needs to be where lapdm.c is
>
> After starting to read the spec (not done yet, so further comments my
> come afterwards), I don't think "hooking" LAPDm is the right way.
>
> From the specs, LAPDm and the SMSCB link layer are not one above the
> other but rather completely separate.
> And again from the spec, should you expect one or the other on a
> channel, you must ignore any packets with the wrong LPD. So AFAIK on a
> CBCH channel if you ever get a LPD=00 it should be ignored and not fed
> to a LAPDm processor. Same thing for a BTS side LAPDm instance if it
> receives a LPD=01 it should be ignored.

I did get confused by that.  I parsed that the LPD field is specified by
LAPDm (TS 04.06), and it indicates a possible sublayer.

Now that I re-read 04.06, it does say that only LPD=00 is valid for
LAPDm, so other values must be other protocols.

[...]

That all makes sense, I'll give it a try.

Thanks for the feedback.




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