HP Vectra Technical Reference Manual page 30

Driver Data Areas
Each driver has an independently specified data area. Some EX-BIOS drivers share the same data
areas. The data areas for the EX-BIOS drivers are above the HP_VECTOR-TABLE and the
HP_ENTRY_CODE shown in figure 2.2. Although each driver has its own data area, the DS for
each driver is stored in the HP_VECTOR-TABLE, and its data area must start at DS:O. Each data
area must reside on a paragraph boundary.
The data area for each driver consists of a driver header, followed by an optional variable storage
area. The variable storage area is unique to each driver. Table 2.5 provides a general description
of the contents of an EX-BIOS driver header.
Each driver's header and/or variable storage area is described in a following section.
Table 2.5
HP_DRIVELHEADER
Variable Offset Type Offset Definition
DH-ATR 0 Word Driver Attribute Field
DH_NAME_INDEX
2
Word Driver String Index Field
DH_V_DEFAULT 4
Word Driver's Default Logical Device Vector
DH_P_CLASS
6
Word Driver's Parent Class
DH_C_CLASS 8
Word Driver's Child Class
DH_V_PARENT OAH Word Driver's Parent Vector
DH_V_CHILD
OCH Word Driver's Child Vector
DH_MAJOR
OEH Byte Sub Address Field
DH_MINOR OFH Byte Sub Address Field
EX-BIOS Driver Headers
The definition of each of these fields is listed in the following. Additional information on these
fields can be found in Appendix G.
~
DH--.-ATR: Each bit in the DH--.-ATR field indicates a property of the
driver for device mapping purposes. These bits are
defined in Appendix G.
ROM BIOS Overview 21