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Date:      Thu, 30 Sep 1999 00:37:38 +0900
From:      KATO Takenori <kato@ganko.eps.nagoya-u.ac.jp>
To:        bde@zeta.org.au
Cc:        nyan@FreeBSD.org, imp@village.org, winter@jurai.net, kato@FreeBSD.org, cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, FreeBSD98-hackers@jp.freebsd.org
Subject:   Re: cvs commit: src/sys/conf files src/sys/i386/conf files.i386 
Message-ID:  <19990930003738A.kato@gneiss.eps.nagoya-u.ac.jp>
In-Reply-To: Your message of "Wed, 29 Sep 1999 03:06:50 %2B1000 (EST)" <Pine.BSF.4.10.9909290231150.7599-100000@alphplex.bde.org>
References:  <Pine.BSF.4.10.9909290231150.7599-100000@alphplex.bde.org>

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Bruce Evans <bde@zeta.org.au> wrote:

> Doesn't this require changing all drivers that currently use the
> bus space functions to be changed to initialise their sc->sc_bsh.base
> instead of their sc->sc_bsh?  This is uglier than casting.

It would be hard work.  But compilng LINT kernel may tell us missing
changes.


> 1) Only one bus type supported, and the tag for that is a compile-time
>    constant.  Otherwise, there will be an extra branch in the bus space
>    routines for getting to the inirect case.  This branch will cost
>    more than indirection on most machines.

Of cource, your method has advantage to performance.  But if we use
your method (using bus_space_foo with zero offset) in a driver, I
think that there isn't much meaing of usinge bus space.  If
performance loss is not negligible, separating such code into MD part
and using inb/outb may solve the problem.  If performance loss is
negligible, using bus_space_foo with non-zero offset could not have
performacne problem.

-----------------------------------------------+--------------------------+
KATO Takenori <kato@ganko.eps.nagoya-u.ac.jp>  |        FreeBSD           |
Dept. Earth Planet. Sci, Nagoya Univ.          |    The power to serve!   |
Nagoya, 464-8602, Japan                        |  http://www.FreeBSD.org/ |
++++ FreeBSD(98) 3.2:   Rev. 01 available!     |http://www.jp.FreeBSD.org/|
++++ FreeBSD(98) 2.2.8: Rev. 02 available!     +==========================+




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