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Date: Thu, 25 Oct 2001 12:02:15 +0200
From: Helge Hafting <helgehaf@idb.hist.no>
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To: Rob Turk <r.turk@chello.nl>, linux-kernel@vger.kernel.org
Subject: Re: [RFC] New Driver Model for 2.5
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Rob Turk wrote:

> Doing so will create havoc on sequential devices, such as tape drives. If
> your system simply suspends, then all is well. Any data that isn't flushed
> yet is buffered inside the tapedrive. But when the system resumes and resets
> the SCSI bus, it will cause all data in the tape drive to be lost, and for
> most tape systems it will also re-position them at LBOT. Any running
> tar/dump/whatever tape process would not survive such a suspend-resume
> cycle.
> 
Well, why reset the scsi bus on resume then?
That seems unnecessary.  At suspend time the devices simply 
don't get more requests. (Except perhaps spin-down 
requests for disks.)  Then nothing much happens.  Eventually
the system wakes up, and requests appear again.  First spin-up
requests, then ordinary io.

Quite a few scsi bioses have an option for not resetting
the bus when booting.  Less delay, and necessary for those
few with a shared scsi bus.  Seems a reset won't be
necessary for suspend/resume either, which is supposed to
be a lighter operation than a reboot.

If your scsi adapter don't support this - it isn't
suspend/resume compatible the way I see it.

Helge Hafting
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