On Sun 26 Jan, Scott Ashcroft wrote:
> On Sat 25 Jan, Mark Brinicombe wrote:
>  
>> Ok the kernel is finding a drive but the drive appears to actually respond
>> as drive 1 rather than drive 0. This may just be a case of a switch on the
>> drive.
> 
> 
> Does the kernel wire up the drive to /dev/fd1* ?
> 
> If not why not?

If I have understood BSD correctly, it will start on the lowest
numbered devices and allocate the ones found successively.

That means that if you only have one device of a type, that will
always end up as device 0 no matter which physical number it
actually is.

Another example that illustrate this is the SCSI bus. If, say, you
have two devices on the SCSI bus; a disc on target ID 4 and a CD-ROM
on device 6, the first partition on the disc will always end up as
/dev/sd0 and the first partition on the CD-ROM will always end up
as /dev/cd0.

In system V Release 4, this is quite different as you are actully
using the controller, target id, LUN and partition as part of the
device. In the above case we would have the two devices as:
/dev/c0t4d0s0	Disc
/dev/c0t6d0s0	CD-ROM

I hope this gives you an idea of how this works.

Kjetil B.
mailto:kjetil.b.thomassen@eunet.no
(My email address used to be: mailto:thomassk@oslo.geco-prakla.slb.com,
and that still works, of course.)