Subject: Re: "esp" driver reorg proposal
To: Guenther Grau <>
From: Leo Weppelman <>
List: tech-kern
Date: 01/27/1997 21:26:53
Guenther Grau wrote:

> [Gordon want's to share esp driver]
> I say, good idea, this makes it look cleaner and increases the
> possibilities to reuse it in different ports, like the sun3x port :-)
> > The machine-dependent code:
> > 	arch/alpha/include/espvar.h
> > 	arch/alpha/tc/esp.c
> > 	arch/sparc/include/espvar.h
> > 	arch/sparc/dev/esp.c
> > 	arch/sun3x/include/espvar.h
> > 	arch/sun3x/dev/esp.c
> Just one question, though. Why does the alpha have a seperate
> directory for each bus, whereas sparc and sun3x don't? Wouldn't
> it be more logical to have seperate directories for busses on
> all architectures? I just had a look at i386 and they have

Since my recent ventures in implementing the isabus interface on
my atari Hades, I think the answer is yes. As it turns out I can
see the possibility for drivers on different busses for the same
kind of card to use different endian approaches for instance. It
turns out that the ISA interface on the atari does some magic
byte-swapping in some parts of the I/O address ranges while the
PCI bus does not. This leads to different 'helper' functions for
each bus.

> these directories as well. Or is there just one bus in sparc
> architectures and thus it didn't get a proper name? I ask
> this, because I know that SUN is working on PCI-based workstations,
> which would introduce another bus to the sparc architecture
> (besides S-bus (and M-bus?)).
> The same holds true for other architectures like the amiga, which
> has a single dev directory.

The atari /dev directory currently holds only drivers that support
hardware that is on the motherboard (mainbus), or cannot easily
be provided by a generic bus driver (like the et4000 console).