Hello,
I’m using the AvStream mini driver with Pin-Centric processing. My device
has four DMA channels. One or more DMA channels can be used at a time. I
want to associate each of these DMA channels with a pin. The way I thought
it makes sense to do this is to create one *pin type* for the filter and
indicate that up to 4 *pin instances* can be created. The structure I used
to this is the KSPIN_DESCRIPTOR_EX structure below:
typedef struct {
const KSPIN_DISPATCH* Dispatch;
const KSAUTOMATION_TABLE* AutomationTable;
KSPIN_DESCRIPTOR PinDescriptor;
ULONG Flags;
ULONG InstancesPossible;
ULONG InstancesNecessary;
const KSALLOCATOR_FRAMING_EX* AllocatorFraming;
PFNKSINTERSECTHANDLEREX IntersectHandler;
} KSPIN_DESCRIPTOR_EX, *PKSPIN_DESCRIPTOR_EX;
Here, I set InstancesPossible to 4, and InstancesNecessary to 1.
When I built this driver, I was a little surprised about the following:
1 Graph edit shows only one pin initially. If I connect this one pin,
another pin appears, up to my InstancesPossible amount. I was hoping all
four would be present.
2 Graph edit only automatically renders the initial pin. In other
words, if I right click on the first pin and select “render pin” it connects
up the graph. Graph edit than shows a second pin. If I click on the second
pin and select “render pin” nothing happens. I was hoping intelligent
connect would work for all pins.
3 There doesn’t seem to be any way to enumerate the number of
*possible* pin instances without iteratively connecting each pin. In other
words, IEnumPins only returns 1 pin initially. If I connect that pin and
rerun IEnumPins, I get another pin and so on.
I’m willing to accept this is just the way it is, but I was hoping someone
out there might have some insight into the proper way to associate each of
my DMA channels with a pin?
Perhaps I should create 4 identical KSPIN_DESCRIPTOR_EX entries instead,
with InstancesPossible=1 and InstancesNecessary=0 for each?
Jason