Subject: Re: Another changer, another changer problem
To: None <firstname.lastname@example.org>
From: Greg A. Woods <email@example.com>
Date: 10/02/1998 00:47:32
[ On Fri, October 2, 1998 at 06:04:19 (+0200), Zdenek Salvet wrote: ]
> Subject: Re: Another changer, another changer problem
> But, what is the 1st SCSI controller attached to the system ?
> SVR4ish IRIX 6.4 on our Origin has changed SCSI controller numbers
> after applying patches to the OS and screwed us even though we had not
> moved any hardware before :-(
You can't blame hardware design failures on the OS! ;-)
You also shouldn't compare IRIX to anything sane! ;-)
> I strongly prefer current NetBSD naming scheme, kernel config is
> much more expressive than integer quadruple.
In theory the hardware bus should be ordered in some way (either by
physical slots, or by address pins/switches on the cards, ROM serial
numbers on the cards [eg. Ether address], etc.) such that the first
controller is easily identifiable both by sight or other manual
inspection, and by the kernel. If some patch to your OS causes the
kernel to count from the other direction suddenly then that's something
you do need to be aware of, but it's not generally a problem.
If you simply can not nail down the probe order of devices by some
consistent physical attribute of those devices, then you're hosed and
you should probably consider switching platforms.
Now, whether you do this ordering on a per-driver basis, or on some more
logical level, such as disks, tapes, serial ports, network interfaces,
etc., is a whole different question.
Personally I like devices with little jumpers or thumbwheel switches so
it doesn't matter which slot you use, or what order they appear on the
bus cable, etc. This goes for cards on a bus, external peripherals, and
Greg A. Woods
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