Path: utzoo!attcan!uunet!munnari.oz.au!metro!ipso!runxtsa!brucee
From: brucee@runxtsa.runx.oz.au (Bruce Evans)
Newsgroups: comp.os.minix
Subject: Specifying floppy types (was Re: minix ST 1.5 patch 3)
Message-ID: <2452@runxtsa.runx.oz.au>
Date: 21 Oct 90 08:24:06 GMT
References: <1990Oct13.120111.21252@math.lsa.umich.edu> <1370@carol.fwi.uva.nl> <1990Oct14.025522.4259@math.lsa.umich.edu>
Organization: RUNX Unix Timeshare.  Sydney, Australia.
Lines: 34

In article <1990Oct14.025522.4259@math.lsa.umich.edu> hyc@math.lsa.umich.edu (Howard Chu) writes:
>Or how about a standard method of telling the device driver (ioctl) the current
>disk geometry?

Such a method (including the whole driver) has already been posted for the ST
by Matthias Pfaller. It's not standard though. I keep the files in my to-do
directory...

I don't like one thing about this approach. The meaning of /dev/fdxyz would
not be fixed, nor would it be related to the current disk. Too many programs
might have to set and restore the device state. They might have to catch
more signals to clean up properly.

>This is what's been holding up the formatting routine for the
>Minix device driver.

Not really. The PC driver essentially does ioctls as writes. The PC floppy
hardware interface for formatting is a bit simpler (and less flexible) and
the data written for format is much like the data for an ioctl, so this
approach was natural. For the ST, you could "write" an extra block with the
format parameters before the blocks with the track data.

There was a good reason for avoiding ioctls in the 1.5 PC formatting interface.
The ioctl interface is weak (there is no way to pass more values than fit in
a message) and I had already changed too many things. I think the ST patch3
now passes a pointer to a user buffer like other *nix's.

My favorite idea for specifying the parameters is to encode them in the
device name. The name space is much larger than the space of minor numbers
so it is easier to make the names meaningful and to specify geometries not
known to the driver. Ast does not like this on the grounds that the names
should have no particular semantics.
-- 
Bruce Evans  (evans@syd.dit.csiro.au)