linux-kernel - Re: [PATCH] x86: tidy e820 output

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Date:	Wed, 22 Sep 2010 16:16:28 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	David Rientjes <rientjes@...gle.com>
CC:	Bjorn Helgaas <bjorn.helgaas@...com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	Yinghai Lu <yinghai@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86: tidy e820 output

On 09/22/2010 04:12 PM, David Rientjes wrote:
> On Wed, 22 Sep 2010, H. Peter Anvin wrote:
> 
>>> This patch is going to break our userspace parsing scripts if you change 
>>> the output format.  Admittedly, we're probably one of the few users who 
>>> actually parses this output, but we do have reasons to do it for our 
>>> firmware.  If there was some improvement being introduced here, we'd 
>>> happily handle multiple regexs (we constantly add new patterns when new 
>>> kernels are released), but I'm not seeing how this is better.
>>
>> Kernel messages are not an ABI or API.
>>
>> The user space API for this stuff is /sys/firmware/memmap.
>>
> 
> I'm referring to using [start, start + addr - 1] in the output, like 
> /sys/firmware/memmap does, as opposed to [start, start + addr].  Is it not 
> valuable to include the actual e820 map in some way, especially when you 
> have your own BIOS?  We've always used this output since it isn't 
> available later.

"The actual e820 map" contains (start, length, type) -- the end bracket
is not part of it at all.  Either way, /sys/firmware/memmap does provide
the memory map as provided by the firmware through whatever means.

> Another use of this information that people may already be using it for is 
> ensuring the memmap= on the command line is parsed correctly.
> 
> So, again, I'm looking for the benefit here in this patch and it's not 
> immediately apparent to me.

Consistency with other resources displayed seems like a major win to me.

	-hpa
	
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