[Asterisk-Dev] best approach for a new isdn driver mainly for asterisk.. ?!

[Andrea Venturi]

hi,

we'd like to set up an asterisk server on a lightweight x86 pc with only 
USB port.

we found this cheap isdn adapter: winbond w6694a

   http://www.winbond.com/PDF/sheet/W6694a.pdf

this seems an actually unsupported by linux usb adapter but it seems 
*bsd supports it 8-)

   http://home.c2i.net/hselasky/isdn4bsd/privat/temporary/

it's passive card so not a plain ACM compatable!

the datasheet seems quite complete WRT register description so i think 
it should be not a though task to try to support this card _but_ i have 
a concern.

actually there are at least three (or four) environment WRT isdn on linux

1- the classical isdn4linux effort (the hisax stack) but it's quite poor 
WRT ISDN signaling if you use the /dev/ttyI* interface and "TE" mode only.

2- the newer capi approach (i heard it should be the default in kernel 
2.5.x and onward but i don't know if it's true today)

3- the zaptel/libpri way: do you think it could be easy to leverage the 
tormenta skeleton? is the ISDN PRI signaling really the same ISDN Q931 
(the D protocol on the BRI signaling channel in euro-land..): i see that 
there's just a different module for the E400P and the E100P.. support 
this new ISDN card could be just as easy as develop this low-level module ?

4- the isdn raw device from http://isdn.jolly.de/ : i know this is not a 
well known and developed kernel support but this has the advantage that 
you can have both NT & TE support for the hfc based card.

IMHO the best approach could be number three (kudos to mark and co.) 
because:

- it's fully GPL
- it's reliable and running _now_ (when will have a capi kernel support 
uncluttered !?)
- it's feature-full (and not poor like the /dev/ttyI* emulation)
- it's both voice & data ready
- it's both NT & TE (in PRI level this is a quite light difference.. 
maybe a PITA in the BRI level..)

on the other end, it's not a well known environment outside the asterisk 
community so it's quite a challenge WRT well established "telco" driver 
in linux world..

what do you think about the topic ?!

bye

andrea venturi