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

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Date:	Thu, 17 May 2007 16:30:44 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
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

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".''

>>> +
>>> +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?

>>> +Field name:	readmode_swtch
>>> +Type:		modify (optional)
>>> +Offset/size:	0x208/4
>>> +Protocol:	2.00+
>>> +
>>> +  Boot loader hook (see separate chapter.)
>>>   
>>>       
>> Chapter?  Is there a more specific reference you could make?
>>     
>
> Fair enough...
>
>   
>>> +Field name:	kernel_version
>>> +Type:		read
>>> +Offset/size:	0x20e/2
>>> +Protocol:	2.00+
>>> +
>>> +  If set to a nonzero value, contains a pointer to a null-terminated
>>>   
>>>       
>> "nil-terminated"? "\0-terminated"?
>>     
>
> Uh?  That seems more than a little silly.  Yes, I guess formally
> speaking we're talking about "NUL-terminated", but the term
> "null-terminated" has over 800,000 hits on Google -- 10 times as many as
> "NUL-terminated" -- and is hardly an ambiguous term ("NUL-terminated" is
> ugly, and "zero-terminated" is ambiguous.)
>   

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

    J
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