Re: using GPT support in BIOS boot

["Mike M. Volokhov" <mike.volokhov%gmail.com@localhost>]

On Mon, 10 Jan 2011 11:24:33 +0100 Martin Husemann wrote:
> On Mon, Jan 10, 2011 at 11:25:54AM +0200, Mike M. Volokhov wrote:
> > Yes, it should be possible with INT 13h AH=48h. It's pretty hard to
> > integrate it into 512 bytes of MBR though, but should be possible to
> > include into libsa and use on later stages. Also, for gpt.S it's
> > possible to use SECTOR_SIZE during compile stage to adjust addressing.
> 
> We need it more in NetBSD userland - if we don't want to align on MB
> boundaries (which would be good enough for me) in the partitioning tools.

Ah, messed it up, sorry.

So, AFAIU sector size can be obtained by getdisksize() which derives it
from either wedge or disklabel, which in turn uses driver reported
sector size or falling back to DEV_BSIZE. But if device reports its
sector size as 512 bytes, it will be quite hard to an operating system
to derive physical size. So IMHO the right approach is to configure a
device to report it's native sector size, yet it's supported by NetBSD
(as I believe) and even BIOS, and then just use getdisksize(), but
probably I'm wrong.

--
Mishka.