[pups] Major/minor device numbers and device names for MSCP drives?

Robert Armstrong bob at jfcl.com
Mon Jun 19 13:15:52 AEST 2006

  Probably this is documented somewhere, but I really need a pointer or a
brief tutorial on the major/minor device numbers for mknod() and the device
names for MSCP drives in 2.11bsd.
  If I have a really simple PDP with an RQDXn and one RDxx disk, then the
device name is conventionally /dev/ra0x and the first partition, ra0a is
(5,0), the second, ra0b, is (5,1), etc.  Pretty easy.
  If I have two drives on my single RQDXn, then the second hard disk is
/dev/ra1 and ra1a is (5,8), ra1b is (5,9), etc.  I guess the offset of 8
must be the maximum number of partitions on a drive - OK, I'm still with
  But what if I have a second MSCP controller?  Assuming that I've built the
kernel to handle it and modified dtab to autoconfigure it, that is.  What
are the usual names and mknod() numbers for the drives on the second
  Worse, what if the MSCP controller isn't a RQDX but is a real UDA/QDA ?
Now the drives have their own MSCP unit numbers that can be anything from 0
to 250 - where does this figure in?
  Same question for TMSCP - what if I have more than one tape controller?
This case is easier, though, since TMSCP controllers normally have only one
drive associated with them.
Bob Armstrong
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