Subject: Re: dev_t changes & partitions
To: Todd Vierling <tv@NetBSD.ORG>
From: Jason Thorpe <>
List: tech-kern
Date: 01/13/1998 21:52:39
On Tue, 13 Jan 1998 22:06:00 -0500 (EST) 
 Todd Vierling <tv@NetBSD.ORG> wrote:

 > : Though who, other than MBR drives, will use slices? I thought other
 > : disklabels will just have oodles of partitions.
 > Amiga (inside RDB structure).  SPARC (SunOS label not big enough?).  Others?

Um... no...

On Amiga (and others that use similar self-describing partition map
formats, like the Mac, I think), you can have arbitrary number of partitions
each with arbitrary IDs.  NetBSD/amiga doens't put a disklabel inside
an RDB partition, but rather uses the RDB partition map directly.

NetBSD/sparc uses NetBSD disklabels, nestled within a block of unused
space in the SunOS disklabel.  It uses the info stored in the SunOS
label if the NetBSD label isn't found.

For all port, we want to use NetBSD disklabels where possible, and fall
back on "vendor" labels if NetBSD labels are not available.

NetBSD/powerpc does something reasonable (although I would have implemented
it differently :-) ... basically, it starts looking for an MBR, and
parses the MBR into a NetBSD disklabel in-core... if it happens to find
a NetBSD disklabel along the way, it assumes that the MBR data is nonsense.
So, to access DOS partitions, you actually describe them in the NetBSD

If you have enough paritions (note, MAXMAXPARITIONS is currently defined
to 22, because any more than that, and the disklabel doesn't fit into
a 512-byte disk sector!), this isn't an issue.

Jason R. Thorpe                             
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