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SubjectRe: ncr53c8xx SCSI driver locks up computer after timeout message
Hi bradley,

On Tue, Feb 23, 1999 at 06:02:41PM -0500, Bradley M. Kuhn wrote:
> Gérard, thank you so much for writing back to me!
> Specifically, what do you mean by 'device disconnecting the SCSI bus'. I
> have disconnections "not allowed". Can it still happen anyway?

I can not comment on most of your questions, but let me explain this one:
Your devices have to disconnect from the bus, when a command has completed.

Now, what is meant by "Disconnection disallowed" means, that your devices
don't disconnect during processing a command. Consider the following, very
unsual situtaion: You want to read 64k from disk. The adapter selects the
hard disk and the SCSI bus is allocated. The command is sent to the disk.
The disk now has to collect the data from it's heads in it's internal cache.
Now, instead of blocking the bus, it could disconnect and thus allowing
other devices to use the bus. This is the disconnection that can be
forbidden. It will reconnect later, when the data iscollected. Now the data
is transfered, messages are exchanged and the device finally disconnects.

The disconnection is just one very nice feature of the SCSI protocol, which
makes it possible to handle a lot of devices on one bus (as opposed to IDE,
BTW).

Regards,
--
Dipl.Phys. Kurt Garloff <kurt@garloff.de> [Dortmund, FRG]
Plasma physics, high perf. computing [Linux-ix86,-axp, DUX]
PGP key: see mailheader / key servers [Linux SCSI driver: DC390]
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