Subject: Re: Where to start?
From: Fabrice Bellard <>
Date: Sat, 10 Apr 1999 02:07:09 +0200


Are you working on modems at 3com ? 

> The idea of a VxD loader is a good way toward the solution. What is needed in
> addition is a VCOMM emulation for the virtual comm port and a partial VM
> emulation for the ring 0 calls that the VxD makes for such things as timer
> callbacks.

With a few patch in each VXD driver, I think it could be doable. But
writing a true Linux GNUmodem is a more satisfying solution.

>   I have a question for you on avoiding the IP for a written from scratch
> driver. There are patents on such things as +++, the AT command set, V.42 BIS,
> MNP2-5 and aspects of V.42. If you are browsing the net, all you need is error
> control, and configuration commands. This could be the opportunity for Linux to
> dump useless heritage modem features?

Yes, I think it is possible to avoid all the patents in the protocol
stuff. It may be even possible to implement V42 without infringing
patents because V42 is only a variation of LAPM, and LAPM has been in
the public domain for a long time.

If we implement only the protocol stuff, we must know how to interface
to the data pump chips. Cooperation with the data pump makers is
unavoidable because the data pumps interface are *really* complicated.
Reverse engineering is clearly impossible.