Re: Why is generic hldc beig ignored? RE:Linux 2.4.22-pre4

=?ISO-8859-1?B?RnJhbnRpc2VrIFJ5c+FuZWs=?= (
Mon, 14 Jul 2003 13:36:15 +0200

Dear Mr. Tosatti,

I've been asked by Mr. Francois Romieu, the author of
to give you a summary of my user-space experience with recent versions
of dscc4.c and the Generic HDLC Layer (drivers/net/wan/hdlc_*.c, hdlc.o).

The message is: it works, to the extent that it can be configured and
TCP/IP works. I've tried DSCC4 hardware back-to-back and against
a Cisco, in a few different configurations. I've tried the three basic
encapsulations: cisco-hdlc, itu-hdlc and sync ppp.
I don't know enough FR and X.25 to be able to come up with a workable
setup (didn't even try).

I was using linux 2.4.21-rc1 and 2.4.21 (release). This works, but that
version of dscc4.c suffers from a hardware quirk in the DSCC4 hardware
- the port/link cannot be reconfigured without a cold reboot.
The effects of this quirk are alleviated by a patch to dscc4.c that has been
submitted by F.Romieu for approval to the linux kernel and that reportedly
has made i to the -ac series, but not to the vanilla 2.4.21.
I have not touched the sources of the Generic HDLC Layer (hdlc*.c) that is
present in 2.4.21-rc1 to 2.4.21. I was using the vanilla source without
modification. I don't know about any differences in the hdlc*.c in the -ac
series - I didn't investigate that flavor.

As for the userspace sethdlc.c by Krzystof Halasa: I was using ver.1.12,
modified by Mr. Romieu, who has "cut some non-compiling functionality."
The current version from Krzysztof Halasa is 1.15.

I barely had the time to test basic workability and document my test bench.
Unfortunately I did not do any stress/long-term/feature-crosscompatibility
Specifically, I was using uniprocessor machines only (no SMP).
I did not test all the features available in the Generic HDLC Layer, I don't
fully understand all the technologies covered - I was only interested in
point-to-point IP over sync serial.

I've written a short mini-HOWTO - the chapter on test results in terms of
transfer rates and ping round trips is at

I hope that I was not completely wasting your time :-)
If you have further questions, ask me.
Thanks for the great job that you're doing.

Sincerely yours

Frank Rysanek

----- Original Message -----
From: "Francois Romieu" <>
To: "Frantisek Rysánek" <>
Sent: Friday, July 11, 2003 9:25 PM
Subject: [ Re: Why is generic hldc beig ignored?
RE:Linux 2.4.22-pre4]

> Imho l-k is waiting for a summary of your experiences with post
> 2.4.21-pre linux hdlc.
> Btw latest dscc4 updates are available in Alan Cox's -ac series.
> ----- Forwarded message from Marcelo Tosatti
<> -----
> From: Marcelo Tosatti <>
> Date: Fri, 11 Jul 2003 14:18:10 -0300 (BRT)
> Subject: Re: Why is generic hldc beig ignored? RE:Linux 2.4.22-pre4
> X-X-Sender: marcelo@freak.distro.conectiva
> To: Henrique Oliveira <>
> Cc: Alan Cox <>,
> Kevin Curtis <>,
> lkml <>
> References: <>
> <Pine.LNX.4.55L.0307101410570.25103@freak.distro.conectiva>
> <003101c34712$a9b8f480$602fa8c0@henrique>
> <013901c347cd$44586f60$602fa8c0@henrique>
> X-Spam-Status: No, hits=-28.7 required=4.0
> version=2.53-fr_1
> X-Spam-Level:
> X-Spam-Checker-Version: SpamAssassin 2.53-fr_1 (
> On Fri, 11 Jul 2003, Henrique Oliveira wrote:
> > Hello !!!
> > No offence here but the generic hdlc layer's been always confusing. I
> > write here what I believe is going on.
> > Until version 2.4.20 we had the old hdlc layer, with only one source
> > hdlc.c. People that wanted to use the new hdlc layer had to apply a
> > provided by Halasa or by the WAN cards vendors. The kernel 2.4.21 came
> > with the new hdlc layer, that includes a couple of files:
> > hdlc_fr.c, hdlc_ppp.c, hdlc_raw.c, etc. I don't know the status of
the -ac
> > tree but I can say that the kernel 2.4.21 has the new code.
> > The new hdlc layer really needs new tools. This new tool can
(supposedly) be
> > found at Halasa's web site. I don't know if someone has tested these
> > but I am about to run a test this afternoon. If someone is interested on
> > results, just drop me a line.
> I am.
> Please report the results of your tests and CC lkml.
> And Alan, what the -ac tree hdlc changes are about ?
> -
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