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Re: Writing device drivers for L4 (was Re: Hurd/Mach on L4)

From: Farid Hajji
Subject: Re: Writing device drivers for L4 (was Re: Hurd/Mach on L4)
Date: Fri, 12 Oct 2001 23:26:41 +0200 (CEST)

> Currently, some of my colleagues are working on a framework that
> allows you to (more or less) drop a Linux driver in a preconfigured
> source tree and get a working driver that runs on the x86 L4 kernels
> (L4/x86, Fiasco, L4KA).  This framework, which will work with the
> L4Env environment we're developing, is not quite ready yet, but it
> might be worth the wait.
Will the drivers run in userland on top of a vanilla L4 kernel?
I'm wondering wether it would be possible to use (RPC?) the driver
tasks directly from OS personalities like L4Linux, (L4BSD if someone
wants to repeat the Lites experience on L4 ;-)) or the Hurd, possibly
even simultaneously?

One example: consider the serial driver. It could be used by the
user-level PPP program on *BSD or the Hurd to access one port, and
by the gpm mouse handler on L4Linux for the other physical port.
Another example: disk drivers could serve filesystems on both
L4Linux and the Hurd (as long as the filesystems are not used

It would be great to have such generally useable drivers resp.
driver tasks!

I see some issues on multiplexing and demultiplexing access from
or to the drivers here (which resembles accessing Mach devices
from multiple Mach tasks in unrelated OSes). Quite interesting!

> As an alternative, consider using the OSKit.  We have developed a
> compatibility library that allows you to run applications using the
> OSKit (including the OSKit's device drivers) on top of L4.  This work
> is a bit unpolished and the drivers are slow, but it's quite easy to
Good point. However, wouldn't it be necessary to link the driver
libs to the Kernel? This is exactly what we want to avoid in the
OSKit-Mach case sometime in the future (*Sigh*).

> use.  I even wrote a technical report on it:
> <URL:http://os.inf.tu-dresden.de/~hohmuth/prj/oskit-l4.ps.gz>.
I'll read this carefully and will get back to you if necessary ;)
Thanks for the hint.

> (You can find this and other reports in the L4 Developer's
> bibliography at <URL:http://os.inf.tu-dresden.de/L4/bib.html>.)
> Michael
> -- 
> address@hidden, address@hidden
> http://www.sax.de/~hohmuth/


Farid Hajji -- Unix Systems and Network Admin | Phone: +49-2131-67-555
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