Configuring HP-UX For Peripherals

Chapter 1 23
Getting Started
Understanding Device Special File Names
Understanding Device Special File Names
Device special files tell the operating system which device driver to use,
how to find the peripheral device, and what characteristics the
peripheral device should employ. Characteristics vary by device. Thus,
device special files for magneto-optical devices show the surface being
addressed, while those for tape drives show rewind and density.
Most device special file names contain the location of the device on the
bus architecture. To see this, display the files in any subdirectory of the
/dev directory. Note, all mass storage devices adhere to a syntax that
includes c#t#d#[s#] (other kinds of device files use a related
convention):
c# represents the card instance number for the class of
interface card to which the device is connected. Classes
of interface cards include ext_bus, graphics, tty, lan,
and others. The card instance of an interface card is
unique for its specific class. There is no relationship
between the instance number and the slot number of
the interface card in the card cage.
Class and instance number can be seen in the first two
columns of /usr/sbin/ioscan -f output. When
interpreting a device special file, the only significant
instance number is the card instance (that is, the
instance number for the class of interface to which a
device is attached). Thus, in a sample disk device file
/dev/rdsk/c1t4d0, the c1 refers to the card instance,
not to an LU number (as in previous releases).
t# represents the target address of the device on the
interface bus. The address can range from 0 to 7 for a
single-ended device, and from 0 to 15 for a fast wide
device. Typically t# is the address set with jumpers or
dip switches on the device itself.
d# represents the device number, and can range from 0
to 7 maximum. On SCSI devices, d# is the SCSI LUN.
Except for multi-function devices, d# is typically d0.
s# specifies section number (optional; made available for
backward compatibility). Note, section 0 now