The kernel communicates with the hardware by associating the
driver name with a hardware address. The kernel identifies the drivers
it needs from the /stand/system file and finds them using the files in the /usr/conf/master.d directory.
All standard HP-UX interface and device drivers shipped are
located in the library /usr/conf/lib/libhp-ux.a.
The kernel recognizes interface and device drivers (and by
extension, peripheral devices) by major and minor numbers encoded
into the device special files.
Each device driver in the system is assigned a major number,
which the kernel uses to locate the driver routine to service an
I/O request.
The driver uses the minor number to locate the specific device
and for information regarding how to handle data.
Major Numbers |
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The major number is an index for the device driver into one
of two kernel tables — bdevsw, the block device switch table and cdevsw, the character device switch table.
Drivers that support both block and character I/O (such as
SCSI disk driver and optical autochanger) have both a block major
number and a character major number. Devices that support only character-mode
access have only a character major number.
The core-hpux file in /usr/conf/master.d contains a Driver install table, which lists major numbers for reference
only.
To identify valid major numbers for devices configured on
your system, you can execute the lsdev command.
lsdev reads the driver headers and lists the drivers
configured into the kernel with their block and character major
numbers. If the driver is designed to use a dynamically assigned
major number, lsdev displays the assigned major number.
Major numbers are displayed in decimal form. The -1 designation in either character or block major
number field of lsdev output can mean:
The device might be a module that
is not a driver.
Driver is not supported in that block or character
mode.
Minor
Numbers |
|
Minor numbers represent two kinds of information: the location
of the interface to which a device is attached and driver-dependent
characteristics. This information is organized by specific bit assignments.
The tables later in this Appendix show the bit assignments
for many HP-UX device drivers. You can also consult the device driver
manpage in section 7 of the HP-UX Reference.
For non-HP drivers, consult the documentation provided with the
driver.
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