[wdmaudiodev] AVStream vs. Portcls

  • From: BlazeAudio Developer <developer@xxxxxxxxxxxxxx>
  • To: WDM Audio Dev List <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Thu, 13 Feb 2003 14:35:06 -0800


We are trying to decide whether to go with AVStream or Portcls for writing
the next version of our MIDI driver.

The underlying device is connected on the 1394 bus. We currently have a
Streaming mini-driver that works well.

However, there are a few things that this driver lacks, that we hope will be
fixed by going to AVStream or a Portcls miniport. Can anybody provide
guidance with the following issues:

1. Multi-client support - (KMixer, KSplitter equivalent for MIDI). I think
PortCls implements multi-client support (merging and splitting MIDI data)
currently. However, Stream.sys does not provide this support. Will the
AVStream based mini driver have to worry about this, or does AVStream
providemulti-client support?

2. Multiple MIDI ports - the device has 8 MIDI ports. With the current
architecture we actually have a separate bus-driver which creates child
devices - and each of the child devices are served by a new instance of the
the stream minidriver. With a PortCls mini-port we can easily add multiple
"devices"(PcRegisterSubdevice) without having to create real child
devices(causing yet another new hardware found wizard), however that's not
possible with the current Stream minidriver model. How does this stand with
an AVStream mini driver?

3. Legacy OS Support - both a stream minidrivers and portcls miniports are
supported on older WDM operating systems, but AVStream is only available on
XP (and Me?). What happens when a user wants to use our device with an older
OS. Do we need to maintain separate drivers? It seems very unlikely that
AVStream will ever be back-ported to Win2K!


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