There are a few different certifications one has to get.
Layer 1 - that the equipment uses the correct voltages and waveforms
Layer 2 - the HDLC/LAPB framing and encapsulation
Lauer 3 - the D-channel protocols used to communicate with the
exchange, with data packets saying things such as SETUP
(place a call), or RELEASE (hang up)
Active cards implement everything from Layer 1 to Layer 3, and have an
onboard CPU with its own firmware. These cards can get a complete
certification since the whole ISDN stack is implemented in them.
Passive cards (i.e. hisax cards) only implement Layer 1 and part of
Layer 2 in hardware, the rest is implemented in software. Here it is
a hardware/software combination that is certified and if the software
changes the Layer 2 + 3 certifications must be redone (in theory at
least, it is somewhat up to the judgement of the manufacturer, minor
changes are allowed).
What this means for the isdn4linux source is that the hisax driver
(Layer 2 and Layer 3, equivalent to the firmware in an active card)
can not be changed and still keep its certification. The upper layer
above this can be changed any way you want.
/Christer
-- Christer Weinigel Cendio Systems AB Email: wingel@cendio.se Teknikringen 8 Phone: +46-13-21 46 00 583 30 Linköping Fax: +46-13-21 47 00 Sweden [please note that Signum Support has changed its name to Cendio Systems]- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/