Path: utzoo!attcan!uunet!mcvax!hp4nl!philmds!nlgvax!johan
From: johan@nlgvax.UUCP (Johan Stevenson)
Newsgroups: comp.os.minix
Subject: Re: MINIX ST: Bug in stwini.c ???
Keywords: Harddisk driver  ACSI bus  stwini.c
Message-ID: <198@nlgvax.UUCP>
Date: 18 Jan 89 19:46:46 GMT
References: <805@faui10.informatik.uni-erlangen.de>
Reply-To: johan@nlgvax.UUCP (Johan Stevenson)
Organization: Philips Research Geldrop
Lines: 24

In article <805@faui10.informatik.uni-erlangen.de> dkhusema@faui49.uucp (Dirk Husemann) writes:
>
>	Hi!
>
>	Just out of curiosity I examined the MINIX ST winchester device driver
>on friday night. There's one place in it which I've trouble understanding why
>it was done the way it's done ...
>
>...

Although I admit I haven't tested it with more than one drive ever,
I still believe the code to be correct. The comment in the file stwini.c
explains the reason, although rather terse.
The current driver supports up to 8 controllers, each having up to
2 drives, each with 8 partitions (4 real partitions, 4 fake).
A minor device number contains the following bit fields:
	0 C C C D P P P
where C=controller, D=drive_on_controller, P=partition_on_drive.
A variable 'drive' contains the following bit fields:
	0 0 0 0 C C C D
In cmdhead() one needs to specify the controller, so (drive>>1).
In cmdtail() one needs to specify the drive_on_controller, so (drive&1).
--
Johan W. Stevenson	johan@pcg.philips.nl		Philips Research