Creating a DriverProc Function

You create a DriverProc function in much the same way as you create a window procedure. The function consists of a switch statement, and each case processes a given driver message, returning a value indicating success or failure. The DriverProc function has the following form:

LONG DriverProc(DWORD dwDriverId, HDRVR hdrvr, UINT msg,
LONG lParam1, LONG lParam2)
{
DWORD dwRes = 0L;

switch (msg) {
case DRV_LOAD:
// Sent when the driver is loaded. This is always
// the first message received by a driver.
dwRes = 1L; // returns 0L to fail
break;

case DRV_FREE:
// Sent when the driver is about to be discarded.
// This is the last message a driver receives
// before it is freed.
dwRes = 1L; // return value ignored
break;

case DRV_OPEN:
// Sent when the driver is opened.
dwRes = 1L; // returns 0L to fail
break; // value subsequently used
// for dwDriverId.

case DRV_CLOSE:
// Sent when the driver is closed. Drivers are
// unloaded when the open count reaches zero.
dwRes = 1L; // returns 0L to fail
break;

case DRV_ENABLE:
// Sent when the driver is loaded or reloaded and
// when Windows is enabled. Install interrupt
// handlers and initialize hardware. Expect the
// driver to be in memory only between the enable
// and disable messages.
dwRes = 1L; // return value ignored
break;

case DRV_DISABLE:
// Sent before the driver is freed or when Windows
// is disabled. Remove interrupt handlers and place
// hardware in an inactive state.
dwRes = 1L; // return value ignored
break;

case DRV_INSTALL:
// Sent when the driver is installed.
dwRes = DRVCNF_OK; // Can also return
break; // DRVCNF_CANCEL
// and DRV_RESTART

case DRV_REMOVE:
// Sent when the driver is removed.
dwRes = 1L; // return value ignored
break;

case DRV_QUERYCONFIGURE:
// Sent to determine if the driver can be
// configured.
dwRes = 0L; // Zero indicates configuration
break; // NOT supported

case DRV_CONFIGURE:
// Sent to display the configuration
// dialog box for the driver.
dwRes = DRVCNF_OK; // Can also return
break; // DRVCNF_CANCEL
// and DRVCNF_RESTART

default:
// Process any other messages.
return DefDriverProc (dwDriverId, hdrvr,
msg, lParam1, lParam2);

}
return dwRes;
}

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