linux-kernel - Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already assigned

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Message-ID: <20100514163416.0e940f64@virtuousgeek.org>
Date:	Fri, 14 May 2010 16:34:16 -0700
From:	Jesse Barnes <jbarnes@...tuousgeek.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Mike Travis <travis@....com>, Bjorn Helgaas <bjorn.helgaas@...com>,
	Mike Habeck <habeck@....com>, Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Jacob Pan <jacob.jun.pan@...el.com>, Tejun Heo <tj@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Yinghai <yinghai.lu@...cle.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	Myron Stowe <myron.stowe@...com>
Subject: Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not
 already assigned

On Fri, 14 May 2010 16:32:07 -0700
"H. Peter Anvin" <hpa@...or.com> wrote:

> On 05/14/2010 04:28 PM, Jesse Barnes wrote:
> > On Fri, 14 May 2010 16:20:45 -0700
> > "H. Peter Anvin" <hpa@...or.com> wrote:
> > 
> >> On 05/14/2010 03:47 PM, Jesse Barnes wrote:
> >>>
> >>> Wow and they're using cards that want to use I/O space?  Funky.  It's
> >>> too late to get this into 2.6.34, but that can't be what you were
> >>> expecting... I don't see a problem with getting something like this in
> >>> for 2.6.35.
> >>>
> >>
> >> Most cards on the market provide I/O BARs as a convenience to legacy
> >> BIOSes; they don't need the I/O BAR functionality from inside a
> >> full-featured OS.  There are a few, key, exceptions, mainly in the form
> >> of legacy-interface devices like UARTs and VGA (note that VGA has its
> >> own routing bits and is therefore unaffected by this problem.)
> > 
> > Yeah, it's the "legacy" part that I'm questioning.  I'm just lamenting
> > that it's dying off so slowly...
> > 
> > And yes, VGA is an unfortunate standard.
> > 
> 
> I'm not lamenting that fact, because my experience is that what ends up
> replacing it is often far worse.  Consider UARTs -- no MMU dependencies
> at all, can be accessed with four lines of assembly, and compare it to
> EHCI debug port, the driver for which is over 900 lines in the Linux
> kernel -- and that assumes that you're already in flat mode.

Heh, you're so old and crufty!

-- 
Jesse Barnes, Intel Open Source Technology Center
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