Configuring a BDA Filter
A BDA minidriver processes method requests of the KSMETHODSETID_BdaDeviceConfiguration method set to configure a filter instance for the minidriver in the current filter graph.
In the following code snippet, two of the methods of the KSMETHODSETID_BdaDeviceConfiguration method set are dispatched directly to the BDA support library and the remaining method is first intercepted by the BDA minidriver before dispatching to the BDA support library.
//
// BDA Device Configuration Method Set
//
// Defines the dispatch routines for the filter level
// topology configuration methods
//
DEFINE_KSMETHOD_TABLE(BdaDeviceConfigurationMethods)
{
DEFINE_KSMETHOD_ITEM_BDA_CREATE_PIN_FACTORY(
BdaMethodCreatePin,
NULL
),
DEFINE_KSMETHOD_ITEM_BDA_DELETE_PIN_FACTORY(
BdaMethodDeletePin,
NULL
),
DEFINE_KSMETHOD_ITEM_BDA_CREATE_TOPOLOGY(
CFilter::CreateTopology,
NULL
)
};
/*
** CreateTopology()
**
** Keeps track of topology association between input and output pins
**
*/
NTSTATUS
CFilter::
CreateTopology(
IN PIRP pIrp,
IN PKSMETHOD pKSMethod,
PVOID pvIgnored
)
{
NTSTATUS Status = STATUS_SUCCESS;
CFilter * pFilter;
ULONG ulPinType;
PKSFILTER pKSFilter;
ASSERT( pIrp);
ASSERT( pKSMethod);
// Obtain a "this" pointer for the method.
//
// Because this function is called directly from the property
// dispatch table, get pointer to the underlying object.
//
pFilter = FilterFromIRP( pIrp);
ASSERT( pFilter);
if (!pFilter)
{
Status = STATUS_INVALID_PARAMETER;
goto errExit;
}
// Let the BDA support library create the standard topology.
// It will also validate the method, instance count, etc.
//
Status = BdaMethodCreateTopology( pIrp, pKSMethod, pvIgnored);
if (Status != STATUS_SUCCESS)
{
goto errExit;
}
// This is where the filter can keep track of associated pins.
//
errExit:
return Status;
}
The KSMETHOD_BDA_CREATE_TOPOLOGY method request calls the minidriver's CFilter::CreateTopology method. This method calls the BDA support library function BdaMethodCreateTopology to create a topology between filter pins. This function actually creates a topology structure in Ring 3, which reflects, for other property sets, the known connections of the filter. A BDA minidriver should intercept the KSMETHOD_BDA_CREATE_TOPOLOGY method request as shown in the preceding code snippet if that minidriver must send special instructions to the hardware when connecting particular pin types--for example, if the BDA device performs hardware demultiplexing and creates an arbitrary number of output pins fanned off from a single input pin.