[syslinux] [PATCH 1/2] Match comment with code
Ady
ady-sf at hotmail.com
Tue Dec 17 10:54:49 PST 2013
> On 12/16/2013 01:41 PM, Ady wrote:
> >
> > 4 January 2010 (newer)
> > e09127r3
> > "EDD-4 Hybrid MBR boot code annex"
> > [quote]
> > Set to the OS Type of the bootable partition (i.e.,
> > that would have been assigned had the partition
> > been installed in an MBR disk layout).
> > [/quote]
> >
> > So, in the older revision, "ED" is explicitly mentioned. In a newer
> > revision there is no explicit mention of an ID code.
> >
> > I still see popular sites with lists of partition IDs with "EE" and
> > "EF" in relation to EFI, and AFAIK there is no (other) "standard" for
> > GPT in BIOS.
> >
> > I wonder whether other documents / standards explicitly mention *any*
> > partition ID, and whether these IDs could potentially result in
> > future inconsistencies / problems / bugs / hours of tracking down
> > strange (mis)behaviors.
> >
>
> You're right - T13 changed the "OS Type" from 0xED to "that would have
> been assigned had the partition been installed in an MBR disk layout".
> That is kind of hard to accomplish without blowing the MBR code size
> budget, since it effectively requires a mapping from GUIDs to OS types.
> In practice I doubt it matters, though.
>
> -hpa
I assume that the intention to use a (theoretical and desired) match
between the partition ID and the filesystem is to "imitate" the
common traditional MBR usage, for a (theoretical) closer backward
compatibility.
Now, if the newer T13 documentation doesn't specifically refer to
"ED" as partition ID for the "hybrid" MBR boot code handover in GPT,
then some questions remain:
_ Is the original desire *not* to use "EE" still relevant?
_ If no particular "matched" ID is used in gptmbr.bin, should "ED"
still be used? I wonder whether it would be better to change it
(back) to "EE" (?).
FWIW, UEFI 2.4 says:
[quote]
0xEE (i.e., GPT Protective) is used by a protective MBR (see 5.2.2)
to define a fake partition
covering the entire disk.
[/quote]
Regards,
Ady.
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