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From: Archie Cobbs <archie@whistle.com>
Message-Id: <199901260451.UAA23212@bubba.whistle.com>
Subject: Re: DEVFS, the time has come...
In-Reply-To: <36AC8477.EDE68A@altavista.net> from Maxim Sobolev at "Jan 25, 99 04:49:27 pm"
To: sobomax@altavista.net (Maxim Sobolev)
Date: Mon, 25 Jan 1999 20:51:14 -0800 (PST)
Cc: current@FreeBSD.ORG, julian@whistle.com (Julian Elischer)
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Maxim Sobolev writes:
> Can you point all people (and me of course) who want to test DEVFS to some
> common information about DEVFS (usage, possible advantages/disadvantages etc.
> I think some FAQ or so will be nice. It's really will help us to go further
> with this issue.

I agree.. and I've bugged Julian to put something together...

Basically, there are a few things that need to be done to get DEVFS
into the 'mainstream'... and this includes SLICE.

The only thing that DEVFS doesn't completely work for right now is
disks, because the way disks are handled right now is all a bunch
of hardwired stuff. SLICE is intended to fix this problem, and in
the process make easy things like a compressed encrypted filesystem
striped across a 10 disk array.. :-)

So the things to do are:

 1. Finish DEVFS-enabling the SCSI "da" disk driver.

 2. Implement asynchronous device management in DEVFS (kernel thread)
    This solves the problem of doing lengthy I/O during interrupts.

 3. Fix the MFS problem -- hopefully Matt Dillon can help here
    in the course of his ongoing cleanups & bug fixes.

 4. Completely rewrite libdisk to use and understand SLICE.
    (This might actually be a kharmically refreshing experience).

 5. Update the installer code to work with the new libdisk
    OR write a "compatibility layer" that implements the old
    libdisk API on top of the new libdisk.

 6. No change to fdisk(8); minor change to disklabel(8).

I'm willing to take a look at the libdisk issue.. in which case
a few helpful pointers from anyone who knows would be nice:

  - What other code beside the installer (if any) uses libdisk?
  - What are the relevant installer files in the source tree?

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com

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