Which partitioning schemes should be supported by GRUB?

[Grégoire Sutre]

Hi,

Tests of GRUB on NetBSD (and FreeBSD) have raised several issues (most
of them reported on the list) regarding partition detection.  However,
I have the feeling that some of these issues are not considered as real
issues since the test configuration is not supported by GRUB.  This
surprises me since I naively thought that most user configurations
should be supported.

So I ask the question: Which partitioning schemes are (or shall be)
supported by GRUB on i386-pc (with standard BIOS)?

To start the discussion, I'll focus on a few examples (the list is
surely not exhaustive).  Maybe some configurations simply cannot exist,
in which case please let me know.

1. A single top-level partition map
   (a) MS-DOS
   (b) GPT
   (c) BSD disklabel
   (d) Apple partition map
   (e) Sun label

2. Hybrid: top-level MS-DOS + another *top-level* partition map
   (a) MS-DOS + GPT
       (i.e. GPT + at-least one non 0xEE MS-DOS partition)
   (b) MS-DOS + BSD
   (c) ...

If I read the code correctly, grub-setup (on i386-pc) only supports
1(a) and 1(b).  However, on NetBSD, 1(c) is very common, and 2(b) is
not rare.  Also, some OSes are fine with 2(a), e.g. FreeBSD.

Personally, I would rather support all possible configurations, unless
some technical reason prevents it.  So grub-setup would not test for
some specific configurations, but would instead use a generic
(and simple) approach.  If it fails, it should be for a good reason,
and not because "No DOS-style partitions [were] found".

What's your opinion?

Grégoire