MappingAvailable is called in two circumstances. The first case is when a
new streaming irp arrives. After the IRP is added to the mapping queue
MappingAvailable is called if the driver is currently starved (the stream
is new or the previous call to GetMapping failed). The second case is in
response to setting the pin position via position property.
The lock issue across GetMapping and ReleaseMapping has been complicated
since the WavePci port was written back in the Win98 days. Unfortunately,
if you attempt to hold a spinlock for your mapping list when you call
these routines you'll likely deadlock with the spinlock that portcls uses
to protect access to it's mapping and unmapping queues.
I don't have the code in front of me at the moment but I'll take a closer
look tomorrow at the portcls and WDK sample code and respond with a little
more detail.
Incidentally, portcls doesn't care at all about your tag values other than
that the outstanding tags at any given moment be unique. They can be
monotonically increasing if you like, or they could be addresses into list
of mappings. It's up to you.
Ken
________________________________________
From: wdmaudiodev-bounce@xxxxxxxxxxxxx [wdmaudiodev-bounce@xxxxxxxxxxxxx]
On Behalf Of Jeff Pages [jeff@xxxxxxxxxxxxxxxx]
Sent: Monday, March 26, 2007 6:58 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: WavePCI issue with multiple processors
Hi Eugene,
A probability of that a new mapping becomes available exactly within
this window, is almost zero.
You're right, of course. I was thinking I had to reacquire my spin lock
after the unsuccessful call to GetMapping, but looking at it now, that's
not
necessary, and I can just call InterlockedDecrement on my
InAcquisitionLoop
variable and exit.
And a well-optimized driver itself cannot guarantee that all Windows
audio subsystems will function quickly and reliably. Even DirectSound
with hardware buffers introduces a significant overhead and software
buffers and/or MME introduce much more overhead. So you can achieve a
reproducible high performance only if your well-optimized application
uses your well-optimized audio driver directly via its wave/topology
interfaces.
For this particular application, I'm using the Vista Core Audio API in
exclusive mode, and this was when some of the wrinkles in my WavePCI
drivers
started showing up. I'm now using your suggestion with the interlocked
InAcquisitionLoop variable and so far it's all hanging in there!
Thanks for your help.
Jeff
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