T-Kernel Specification (1.B0.02)

226 CHAPTER 5. T-KERNEL/SM
5.3 Device Management Functions
5.3.1 Basic Concepts
Applications/Subsystems
↓ Application interface (Extended SVC)
↑
Device Management Functions T-Kernel/SM
↓
↓ Devie driver interface
Interface Layer
↑
Logical Layer
Device Driver
Physical Layer
↓
Figure 5.1: Device Management Functions
(1) Device Name (UB* type)
A device name is a string of up to 8 characters consisting of the following elements.
#define L_DEVNM 8 /* Device name length */
Type Name indicating the device type
Characters a to z and A to Z can be used.
Unit One letter indicating a physical device
Each unit is assigned a letter from a to z in order starting from a.
Subunit One to three digits indicating a logical device
Each subunit is assigned a number from 0 to 254 in order starting from 0.
Device names take the format type + unit + subunit. Some devices may not have a unit or subunit, in
which case the corresponding field is omitted.
A name consisting of type + unit is called a physical device name. A name consisting of type + unit +
subunit may be called a logical device name to distinguish it from a physical device name. If there is
no subunit, the physical device name and logical device name are identical. The term “device name”
by itself means the logical device name.
A subunit generally refers to a partition on a hard disk, but can be used to mean other logical devices
as well.
Examples:
hda
hda0
fda
rsa
kbpd
Hard disk (entire disk)
Hard disk (1st partition)
Floppy disk
Serial port
Keyboard/pointing device
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T-Kernel 1.B0.02