Subject: Re: Proposed extension to bus.h interface
To: None <>
From: Mike Long <>
List: tech-kern
Date: 08/28/1996 13:30:39
>From: Jason Thorpe <>
>Date: Tue, 27 Aug 1996 20:44:55 -0700

>On Thu, 15 Aug 96 18:25:02 EDT 
> Mike Long <> wrote:

> > The minimum and maximum addresses would also be useful for
> > bus_mem_alloc().  10-bit decoding is a silly ISA-bus artifact, so it's
> > only needed for I/O allocation.
>The "start", "end", and "don't cross this boundary" arguemnts have been a 
>common request :-)

No surprise.  The ISA bus has the 10-bit decoding issue.  Other buses have
similar issues, e.g. machines (Alpha?) that use separate memory
regions to access the same physical memory by byte, by word, &c.

> > BTW, how does your extent system handle 10-bit I/O decoding now?  Does
> > it just assume that any I/O port ranges in the [0,0x3ff] range use
> > 10-bit decoding?
>Err, the extent manager literally just mucks with extents of space, and 
>knows nothing about the underlying encoding... You're the first person to 
>bring this up, actually :-)

It's probably better to keep the extent manager as simple as possible.
Let the bus_{mem,io}_alloc() functions deal with mapping all of the
aliases of a given region, because aliasing is bus-specific.
Mike Long <>     <URL:>
VLSI Design Engineer         finger for PGP public key
Analog Devices, CPD Division          CCBF225E7D3F7ECB2C8F7ABB15D9BE7B
Norwood, MA 02062 USA       (eq (opinion 'ADI) (opinion 'mike)) -> nil