linux-kernel - Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override

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Date:	Mon, 31 Dec 2007 13:11:12 +0000
From:	Pavel Machek <pavel@....cz>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Rene Herman <rene.herman@...access.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	dpreed@...d.com, Islam Amer <pharon@...il.com>, hpa@...or.com,
	Ingo Molnar <mingo@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: provide a DMI based port 0x80 I/O delay override

On Sun 2007-12-30 21:46:50, Ingo Molnar wrote:
> 
> * Alan Cox <alan@...rguk.ukuu.org.uk> wrote:
> 
> > > So the current plan is to go with an io_delay=udelay default in v2.6.25, 
> > > to give this a migration window, and io_delay=none in v2.6.26 [and a 
> > > complete removal of arch/x86/kernel/io_delay.c], once the _p() uses are 
> > > fixed up. This is gradual enough to notice any regressions we care about 
> > > and also makes it nicely bisectable and gradual.
> > 
> > You will break systems if you blindly go around disabling _p delays 
> > for ISA and LPC bus devices. The DEC Hinote laptops for example are 
> > well known for requiring the correct ISA and other keyboard controller 
> > delays. I don't expect anyone to test with a hinote or see it until it 
> > hits Debian or similar 'low resource' friendly devices.
> 
> well, using io_delay=udelay is not 'blindly disabling'. io_delay=none 
> would be the end goal, once all _p() API uses are eliminated by 
> transformation. In drivers/ alone that's more than 1000 callsites, so 
> it's quite frequently used, and wont go away overnight.

IOW elimination of broken inb_p()/outb_p() interfaces is the ultimate
goal. Agreed.

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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