HP Vectra Technical Reference Manual page 450

G. 7 Driver Headers
The EX-BIOS driver header (HP_SHEADER) is a formatted data structure similar to the DOS
device driver's header. It defines the attributes of a driver, defines the linkage of a driver and
identifies the driver. It also allows the programmer to define how the driver links with other
drivers.
All EX-BIOS drivers must have an HP_SHEADER. Programmers are not required to provide a
complete HP_SHEADER to use the HP_VECTOLTABLE. But, if they choose to take advantage
of the advanced features of the EX-BIOS the programmer must implement a complete
HP_SHEADER. Table G.5 shows a complete driver header and what fields must be present.
Table G.4
Driver Header Table
Variable Offset Type 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 Subaddress Field
DH_MINOR** OFH Byte Subaddress Field
*This is the only field required for a driver to be in the HP_VECTOLTABLE.
**These fields are only required by drivers that want to do device mapping.
Driver Writer's Guide 441