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: <4C0021DC.60608@zytor.com>
Date:	Fri, 28 May 2010 13:04:44 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Mike Travis <travis@....com>
CC:	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Jacob Pan <jacob.jun.pan@...el.com>, Tejun Heo <tj@...nel.org>,
	Mike Habeck <habeck@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 1/1] x86 pci: Add option to not assign BAR's if not already
 assigned

On 05/28/2010 10:10 AM, Mike Travis wrote:
> 
> 
> H. Peter Anvin wrote:
>> On 05/28/2010 09:53 AM, Mike Travis wrote:
>>> Any further consideration for this patch, or has it been rejected?
>>
>> Well, it's really up to Jesse, but as far as I can see, this patch is a
>> net loss of functionality and doesn't actually add anything.  Without
>> this patch, some resources that were not assigned by BIOS will be
>> unreachable.  With this patch, *all* resources that were not assigned by
>> BIOS will be unreachable...
>>
>> 	-hpa
>>
> 
> Apparently you're missing the point of the patch?  The patch is needed
> because BIOS is purposely not assigning I/O BAR's to devices that won't
> use them, freeing up the resource for devices that do need them.  Where
> is the "all" resources that are not reachable?
> 

No, the patch isn't needed for those.

Without your patch:

- Devices assigned by BIOS remain assigned;
- Devices not assigned by BIOS get assigned until address space
  exhausted.

With your patch:

- Devices assigned by BIOS remain assigned;
- Devices not assigned by BIOS never get assigned at all.

What am I missing here?

	-hpa

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