Subject: Re: toe in the water
To: Darrin B. Jewell <>
From: David Griffiths <>
List: port-next68k
Date: 08/16/1999 12:19:09
Darrin B. Jewell wrote:
> der Mouse  <mouse@Rodents.Montreal.QC.CA> writes:
> > - What is the state of SCSI support?  As of yesterday morning, -current
> >    still had the SCSI stuff commented out in GENERIC, but on the other
> >    hand I recently was told face-to-face that it now works (albeit by
> >    someone not directly involved in the port as far as I know).  The
> >    web pages seem to imply that progress has been made but that it's by
> >    no means ready for prime time yet.
> SCSI is not working.  1.4 shipped with the current hacked-up state of
> the driver commented out in GENERIC.   If you turned it on, it would probe
> the scsi chain successfully and even try to i/o operations, but transfers
> were unreliable, and would result in dropped bytes.  This is where my meager
> time goes when I get some to work on it, but we still have no documentation
> on the dma chip or how it interacts with the ncr53c90a scsi device.  Last
> week I shifted to trying to do dma to a single continuous bounce buffer,
> and may eventually have a slow but working scsi driver with that approach.
> If people are interested, perhaps I should begin a discussion here
> that includes my understanding of the dma hardware.  Someone else
> co-hacking on the dma driver and scsi support will hopefully keep the
> effort from stalling on my slow progress.

As mentioned in a previous message, I'm soon going to be working on the
port of Linux to black hardware. At the moment I'm writing a boot
loader. The idea is that you boot this from the main disk and it will
then load the Linux kernel from the same disk. So it has to do SCSI.
I've had a chance to examine the Plan 9 source and as a result this
weekend managed to get SCSI inquire plus a read of the disk label
working. It's slightly easier in my case because I don't make use of the
MMU. But there is strange stuff going on in the Plan 9 SCSI driver, with
comments such as "NeXT Brain Damage"! I know porting to black hardware
was a "painful" operation for them so studying their source could
probably save you a lot of grief. I can tidy up and send you what I've
done so far if you like, it may contain the vital clue. On the other
hand I've only read the first block and verified that it contains a
label in the right place and so on, so there's no gaurantee it doesn't
suffer the same problems as yours.