linux-kernel - Re: [PATCH] Further update of the i386 boot documentation

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Date:	Thu, 17 May 2007 16:35:14 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Linux Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Further update of the i386 boot documentation

Jeremy Fitzhardinge wrote:
> H. Peter Anvin wrote:
>> Given that we have already established littleendian byte order, it's the
>> same thing.
>>   
> 
> Well, not quite; mentioning the string form first creates an ambiguity. 
> I'd express as something like: ``The magic number is 0x53726448
> (implicitly, stored little-endian), which breaks down to the characters
> "HdrS".''

It does not create any ambiguity whatsoever.  The two are equivalent
forms, and either is authoritative.

>>>> +
>>>> +Field name:	version
>>>> +Type:		read
>>>> +Offset/size:	0x206/2
>>>> +Protocol:	2.00+
>>>> +
>>>> +  Contains the boot protocol version, e.g. 0x0204 for version 2.04.
>>>>   
>>>>       
>>> So the version is in BCD?
>>>     
>> Valid objection.  It probably should be considered as (major, minor)
>> bytes, but we haven't had any releases where it hasn't also been valid
>> BCD.  I would prefer separate bytes myself, so 2.10 = 0x20a instead of
>> 2.10 = 0x210.
> 
> OK.  So is the major or minor at the lower address?

Minor.  Littleendian.

> 0x00 or \0-terminated is idiomatic and unambigous.  Not a big deal
> either way.

Null-terminated is idiomatic and unambiguous.

	-hpa
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