Re: Sync PPP layer

John Heil (
Fri, 27 Jun 1997 16:30:22 +0000 (GMT)

On Fri, 27 Jun 1997, Jan Kasprzak wrote:

> I am writing a driver for a synchronous serial card. I wonder if
> Linux kernel has any kind of generic sync PPP layer (and if it has,
> where I can read more about its interface). I have found some sync PPP stuff
> in ISDN tree, but it seems to work on ISDN devices only. There is
> a generic HDLC/LAPB layer. I think there should be something similar
> for sync PPP. How can I run Sync PPP on top of a generic character device?

I've been using a Sangoma 508 sychronous PPP card on a standard 56k
digital line since my local phone lines went in the can.

Their driver is on their web site in source form :-), and assembles
as a modules as opposed to a kernel patch (:-). Their site is It has both a firmware module that is protocol specific
and a driver. Doc is ok. I've encountered a x'02' return code (card
lethal) occasionally, that brings the card down hard. It seems poorly
doc'd but I don't know the bits and bytes of synch chips (USRT's) and
don't have the time to track it down.

Oh, the card also supports frame relay and IBM's SDLC.

The current kernal code has older support for this card in frame relay
mode I think, but did not bother with it.

The native kernel source is in /drivers/net/sdla.c and maybe one other
since a firmware load is required.

John Heil
South Coast Software