Subject: Re: MI bus ops(Re: 16bit aligned NS16550 variant)
To: TAKEMURA Shin <email@example.com>
From: Jason R Thorpe <firstname.lastname@example.org>
Date: 11/09/2001 08:01:58
On Sun, Nov 04, 2001 at 11:24:41AM +0900, TAKEMURA Shin wrote:
> In the last discussion, I found that function vector definition of
> bus_space method should be michine independent.
Yes, agree here.
> I've rewrote hpcmips bus.h and made new MI header, bus_ops.h
> which contains function vector definitions. I recomend you to rewrite
> your port's bus.h with bus_ops.h, however, I don't force to rewrite all
> ports' bus.h with bus_ops.h.
> I'd like to put bus_ops.h into sys/dev. (I mean sys/dev/bus_ops.h)
> How do you think?
> If no one objecs, I will commit this header in a few days.
So, the bus_space_ops, while independent, don't actually contain enough
info for MI code to construct its own bus_space_tag_t's. This is because
bus_space_tag_t's still have a machine-dependent definition.
I think what I'd really like to see here is for <machine/bus.h> to be
Included as <machine/bus.h> is now. Defines the
bus_space_tag_t, bus_dma_tag_t. Each has the
ops pointers and a void *cookie. If <machine/bus_types.h>
does not define __BUS_SPACE_MD_CALLS, then it defines
the macros that actually call the bus_space methods.
This allows MD code to simply use pointer derefs for
certain types of space, if it wants to.
Included by <sys/bus.h>, defines various types that
<sys/bus.h> needs. Also optionally defines things
like __BUS_SPACE_FAST_ABI (which might e.g. define
a faster ABI to be used for bus space methods, such
as regparm on the x86).
-- Jason R. Thorpe <email@example.com>