Minix 3 subpartition/filesystem patch

[Fam Zheng]

Hi all,

As a project of GSoC of MINIX community, we have almost completed the work making MINIX 3 Multiboot compliant. I believe it would be very helpful for us if GRUB can handle MINIX 3's subpartition and filesystem correctly in the future, so I've made a patch for reading the currently in use MINIX subpartition, so as to make GRUB Multiboot access the OS kernel image. This patch has already been used for a while in our development, to load and test MINIX kernel, and I think now it's ready to be submitted here.

There are two parts of the patch. First part is on fs/minix.c which is changed to support the latest MINIX FS version 3 (previously only version 2 is supported). The other part is on partmap/msdos.c, the changes are made for the following reason:

AFAIK there are two kinds of subpartition, one is from BSD, the other is MINIX. With the latest trunk source, the subpartition is found by GRUB, partition names like (hd0,msdos1,msdos1) can be recognized, but the problem is the 'start' of partition: in the partition table for MINIX subpartitions (the table found at the end of the first sector of (hd0,msdos1) in this example), the field "start" is treated as an relative value, where for MINIX it is actually an absolute one. 

To solve this inconsistency, I patched partmap/msdos.c to convert the value stored on harddisk to relative simply by a subtraction, this happens only when a MINIX type (type field == 0x81) subpartition is encountered.

Thank you.

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Best Regards!
Fam Zheng

minix_support.patch
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