On Tuesday 15 February 2005 10:02, Eric Siegerman wrote:
>On Tue, Feb 15, 2005 at 10:53:55AM +0100, Geert Uytterhoeven wrote:
>> I thought[*] 7 was the highest priority, and 0 the lowest (on a
>> narrow channel).
>
>That's what I recall too.
>
>> Wide devices have an even lower priority: 15 to 8.
>
>This sounds vaguely familiar too, but I'm *far* less certain
>about it.

The bus scan at bootup starts at 0, thats true, but I'm not aware that 
any device number has a 'higher priority'.  As far as the driver 
scanning the bus to see who yelled when the ATN line gets pulled 
down, I don't think its done that way at all as the ACK or whatever 
that comes back then causes the device thats waving its hand to put 
its address on the bus.  So there isn't even a priority there that I 
know of.  If another device also puts up its hand, then I think it 
gets read for the device number and otherwise queued, and will be 
serviced as soon as the first device has been told what to do.  The 
scsi bus multitasks very well indeed in well written code.  Every 
device, including the controller, should have collision avoidance 
built in since thats a basic part of the scsi specs.

-- 
Cheers, Gene
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