Subject: Re: CVS commit: syssrc
To: Chris G. Demetriou <email@example.com>
From: Ben Harris <firstname.lastname@example.org>
Date: 10/16/2000 17:53:33
On 16 Oct 2000, Chris G. Demetriou wrote:
> > - At the moment, the upc driver reads the chip's configuration registers,
> > and uses the results to locate the child devices. Is this sensibly
> > possible with an isa attachment? If not, we have to fall back to
> > probing for each device, which is grotty.
> hence my comment about doing a direct-config variant of ISA, which is
> what you want if you don't want each device to probe.
What do you mean by "a direct-config variant of ISA" that makes it
different from what upc (or amiga supio) currently uses (if anything)?
> > - Devices attached at isa are expected to call bus_space_map themselves,
> > which means the relevant bus_space_tag_t has to contain enough
> > information to locate the UPC in the system's I/O space. This is
> > probably only a problem if you use a very simple bus_space
> > implementation, though.
> I don't think i understand the issue you're facing. do you have a
> non-flat I/O space, or what?
Well, at the moment, the arm26 calculates the I/O address as:
handle + (offset << tag)
This means that a tag doesn't hold enough information to identify
somewhere in the address space. This is arguably a bug in the arm26
> if it's effectively flat, you could go the route where the I/O
> addresses are large numbers, rather than small numbers. 8-)
Could do. I only use two or three bits of the tag at the moment, after
Ben Harris <email@example.com>
Portmaster, NetBSD/arm26 <URL:http://www.netbsd.org/Ports/arm26/>