LPI Linux Certification in a Nutshell (3 page)

One of the basic functions of the BIOS is to manage the
on-board hardware
clock. This clock is initially set in the BIOS
configuration by entering the date and time in the appropriate fields.
Once set, the
internal clock keeps track of time and makes the time
available to the operating system. The operating system can also set
the hardware clock, which is often useful if an accurate external time
reference, such as an NTPD server (see
Chapter 16
), is available
on the network while the system is running.

Another fundamental configuration item required in BIOS settings
is the selection of storage devices. Newer systems are able to detect
and properly configure much of this hardware automatically. However,
older BIOS versions require
manual configuration. This may include the selection of
floppy disk sizes and
disk drive
parameters
.

Most PCs have at least three
bootable media types: an internal hard disk (IDE or
SCSI, or perhaps both), a CD-ROM drive (again IDE or SCSI), and a
floppy disk. After initialization, the BIOS seeks an
operating system (or an operating system loader, such as the
Linux Loader [LILO]) on one or more of these media. By
default, many BIOS configurations enable booting from the floppy or
CD-ROM first, then the hard disk, but the order is configurable in the
BIOS settings.

In addition to these default media types, many
server motherboard BIOS (as well as high-end system
motherboards) support booting from a network device such as a NIC with
a bootable ROM. This is often used when booting
diskless workstations such as Linux-based
terminals.

When adding new hardware to an existing Linux system,
you may wish to verify which resources the existing devices are using.
The
/proc
filesystem, the kernel’s status
repository, contains this information. The
proc
files,
interrupts
,
dma
, and
ioports
, show how system resources are currently
utilized. (These files may not show devices unless their device
files/drivers are open/active. This may make the problem harder to
find if you’re experiencing resource conflicts.) The following is an
example of
/proc/interrupts
from a dual-CPU
system with an Adaptec dual-AIC7895 SCSI controller:

#
cat /proc/interrupts
CPU0       CPU1
0:   98663989          0          XT-PIC  timer
1:      34698      34858    IO-APIC-edge  keyboard
2:          0          0          XT-PIC  cascade
5:       7141       7908    IO-APIC-edge  MS Sound System
6:          6          7    IO-APIC-edge  floppy
8:   18098274   18140354    IO-APIC-edge  rtc
10:    3234867    3237313   IO-APIC-level  aic7xxx, eth0
11:         36         35   IO-APIC-level  aic7xxx
12:     233140     216205    IO-APIC-edge  PS/2 Mouse
13:          1          0          XT-PIC  fpu
15:      44118      43935    IO-APIC-edge  ide1
NMI:          0
ERR:          0

In this example, you can see that interrupt 5 is used for the
sound system, so it isn’t available for a second parallel port. The
two SCSI controllers are using interrupts 10 and 11, respectively,
while the Ethernet controller shares interrupt 10. You may also notice
that only one of the two standard IDE interfaces is enabled in the
system BIOS, freeing interrupt 14 use for another device.

Here are the
/proc/dma
and
/proc/ioports
files from the same system:

#
cat /proc/dma
0: MS Sound System
1: MS Sound System
2: floppy
4: cascade
#
cat /proc/ioports
0000-001f : dma1
0020-003f : pic1
0040-005f : timer
0060-006f : keyboard
0070-007f : rtc
0080-008f : dma page reg
00a0-00bf : pic2
00c0-00df : dma2
00f0-00ff : fpu
0170-0177 : ide1
02f8-02ff : serial(auto)
0370-0371 : OPL3-SAx
0376-0376 : ide1
0388-0389 : mpu401
03c0-03df : vga+
03f0-03f5 : floppy
03f7-03f7 : floppy DIR
03f8-03ff : serial(auto)
0530-0533 : WSS config
0534-0537 : MS Sound System
e800-e8be : aic7xxx
ec00-ecbe : aic7xxx
ef00-ef3f : eth0
ffa0-ffa7 : ide0
ffa8-ffaf : ide1

Universal Serial Bus (USB) is a type of interface used to
connect various types of peripherals, ranging from keyboards and mice
to hard drives, scanners, digital cameras, and printers. The USB
Objective covers the general architecture of USB, USB modules, and
configuring USB devices.

• Open Host Controller Interface (OHCI)
  

• Universal Host Controller Interface (UHCI)
  

• Enhanced Host Controller Interface (EHCI)
  

Human Interface Device (HID)

Input devices (mice, keyboards, etc.)

Communications device

Modems

Mass storage device

Disk devices, flash readers, etc.

Audio

Sound devices

IrDA

Infrared devices

Printer

Printers and USB-to-parallel cables

There is
no
kernel USB support in 2.0.x and
earlier.

Host controller drivers

The USB host controller drivers include
usb-ohci.o
(OHCI driver),
usb-uhci.o
(UHCI driver),
uhci.o
(old “alternate” UHCI driver), and
ehci-hcd.o
(EHCI driver).

Class drivers

The USB class drivers include
hid.o
,
usb-storage.o
(mass storage driver),
acm.o
(Automated
Control Model [ACM] communications class driver, which deals with
modems that emulate the standard serial modem
AT
command interface),
printer.o
, and
audio.o
.

Other
device drivers

There are many drivers for devices that either don’t fit
into one of the standard USB classes or don’t work with one of the
standard class drivers. Examples include
rio500.o
(the driver for the Diamond Rio 500
MP3 player) and
pwc.o
(the driver for various
Philips webcams).

Although not covered on the LPI exams, the Linux
IEEE 1394 (also known as
FireWire or
i.Link) drivers have a similar design. If you understand
how to set up USB devices, setting up IEEE 1394 devices should be
easy.