From owner-freebsd-current  Mon Jan 24 18: 4:39 2000
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Date: Mon, 24 Jan 2000 21:04:33 -0500 (EST)
From: Luoqi Chen <luoqi@watermarkgroup.com>
Message-Id: <200001250204.VAA14309@lor.watermarkgroup.com>
To: kato@ganko.eps.nagoya-u.ac.jp
Subject: Re: indirection in bus space
Cc: FreeBSD-current@FreeBSD.ORG, FreeBSD-hackers@FreeBSD.ORG,
	FreeBSD98-hackers@jp.freebsd.org, nyan@jp.freebsd.org
Sender: owner-freebsd-current@FreeBSD.ORG
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> > Why have two files bus_at386.h and bus_pc98.h? I386_BUS_PIO_IND should be
> > able to live with I386_BUS_PIO and I386_BUS_MEMIO happily together.
> 
> Because they are different in the type of bus_space_tag_t from each
> other.  It is the u_long in PC/AT and the structure in PC-98.  For
> example, bus_space_read_1()s of them are:
> 
>   PC/AT:
> 	bus_space_read_1(...)
> 	{
> 		...
> 		return (inb(handle + offset));
> 		...
> 	}
> 
>   PC-98:
> 	bus_space_read_1(...)
> 	{
> 		...
> 		return (inb(bsh.bsh_iat[offset]));
> 		...
> 	}
> 
You could set the handle to point to the structure instead:
	bus_space_read_1(...)
	{
		if (tag == I386_BUS_PIO) {
			return (inb(handle + offset));
		} else if (tag == I386_BUS_PIO_IND) {
			struct bus_space_handle_pc98 *bsh = handle;
	 		return (inb(bsh->bsh_iat[offset]));
		} else if (tag == I386_BUS_MEMIO) {
			...
		}
	}

-lq


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