Re: [PATCH] x86: documentation fix regarding boot protocol

[Philipp Kohlbecher]

Ian Campbell wrote:
> On Sun, 2008-12-14 at 18:50 +0100, Philipp Kohlbecher wrote:
> > Documentation/x86/boot.txt describes payload_offset as the offset
> > from the end of the real-mode code. In fact, it is more accurately
> > described as the offset from the beginning of the protected-mode
> > code, as (a) this is how it is actually calculated and (b) the padding
> > after the real-mode code is not included in the offset.
> >
> > Signed-off-by: Philipp Kohlbecher <xt28@xxxxxx>
>
> Acked-by: Ian Campbell <ijc@xxxxxxxxxxxxxx>
>
> The padding after the real-mode code which you mention is just the
> implicit padding because the size of the real-mode code is specified in
> sectors (and hence is rounded up), isn't it?

Yes, it is. You can certainly view the padding as an implicit part of 
the real-mode code, which is why the current statement isn't wrong -- 
there is simply room for improvement.

> Is it worth saying that the payload_offset is relative to (setup_sectors
> +1) * 512?

The fact that the protected-mode code starts at that address is already 
mentioned under the heading "LOADING THE REST OF THE KERNEL" (where 
protected mode is for some reason referred to as "non-real-mode").
(Please note that the header field is called "setup_sects", not 
"setup_sectors".)

> > ---
> >
> >   Documentation/x86/boot.txt |    4 ++--
> >   1 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
> > index 83c0033..414b6fb 100644
> > --- a/Documentation/x86/boot.txt
> > +++ b/Documentation/x86/boot.txt
> > @@ -537,8 +537,8 @@ Type:		read
> >   Offset/size:	0x248/4
> >   Protocol:	2.08+
> >
> > -  If non-zero then this field contains the offset from the end of the
> > -  real-mode code to the payload.
> > +  If non-zero then this field contains the offset from the beginning
> > +  of the protected-mode code to the payload.
> >
> >     The payload may be compressed. The format of both the compressed and
> >     uncompressed data should be determined using the standard magic

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