To: linux-kernel@vger.kernel.org
Path: gatekeeper.tmr.com!davidsen
From: davidsen@tmr.com (bill davidsen)
Newsgroups: mail.linux-kernel
Subject: Re: Can we kill f inb_p, outb_p and other random I/O on port 0x80, in 2.6?
Date: 23 Sep 2003 18:41:28 GMT
Organization: TMR Associates, Schenectady NY
Message-ID: <bkq44o$f47$1@gatekeeper.tmr.com>
References: <20030922153651.16497.qmail@science.horizon.com> <m1brtck6wq.fsf@ebiederm.dsl.xmission.com> <20030922215432.GE29869@mail.jlokier.co.uk>
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In article <20030922215432.GE29869@mail.jlokier.co.uk>,
Jamie Lokier  <jamie@shareable.org> wrote:
| linux@horizon.com writes:
| > > So can we gradually kill inb_p, outb_p in 2.6?  An the other
| > > miscellaneous users of I/O port 0x80 for I/O delays?
| > 
| > Actually, It's not easy.  The issue got debated a lot a few years ago.
| > A read is also acceptable, and allows a few more ports to be
| > potentially used, but that corrupts %al and thus bloats the code.
| 
| It bloats the code a lot less than udelay() calls or any other
| solution which keeps the delay!
| 
| In the worst case, the bloat from a read _should_ be two bytes: "push
| %eax; inb $80,%al; pop %eax".  Whereas a call to udelay is 5 bytes,
| for a call instruction.

Isn't one of the benefits of a rethink not to use any i/o bus cycles?

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.
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