Re: adding support for logical partitions to wd

Andy,

> .... If you understand this stuff, it would be good to
> teach it to VSTa. Maybe in wd, maybe somewhere else. More on this in
> a second.

Well, one of the DOS programming books that have just touches on this
subject. Beyond that, I just dumped a number of sectors. What I saw
seemed to be reasonable - it looked like the extended partition did in
fact have 3 logical partitions and one logical partition began just
after the previous one ended. I'll try to find a better source of
information for this.

> If I understand what you're implying, logical partitions under an extended
> partition use the same format as the boot sector for the disk? Now this is
> getting crazy, but can an extended partition hold an extended partition?
> That is, is this arbitrarily recursive, or bounded for a depth of two?

I don't think the scheme is recursive. The extended partition can
contain one or more logical partitions, and that's it.

> What I would do is break out the part which walks through a block
> describing partitions, and make it a standalone routine. Then call
> this routine once for the boot block, and once again for each extended
> partition.

> Arguments to the routine would need to include a prefix string, the sector
> buffer, a pointer to a struct disk, and a count of struct disk's available.
> Once you have this working, consider moving the interpretation stuff over
> to lib/libusr.a. We eventually will have other hard disk drivers, and
> it would be nice to share this code among all of them.

Ok, I'll try this.

                                        Mike Larson
Received on Wed Sep 1 11:34:00 1993