The DRV_OPEN message is sent to an installable driver each time it is opened.
dwDriverIdentifier
Specifies a unique 32-bit value that identifies the installable driver.
hDriver
Identifies an instance of the installable driver.
lParam1
Points to a null-terminated string containing any ASCII characters that followed the driver name in the SYSTEM.INI file.
lParam2
Contains the data specified by the lParam parameter, the third argument in the OpenDriver function.
An installable driver returns nonzero if it processes this message. Otherwise, it returns zero.
If no characters follow the driver name in SYSTEM.INI, the lParam1 parameter is a NULL pointer.