[wdmaudiodev] Re: AVStream and WDF
- From: Tim Roberts <timr@xxxxxxxxx>
- To: wdmaudiodev@xxxxxxxxxxxxx
- Date: Mon, 26 Oct 2009 09:45:42 -0700
KS wrote:
>
> Is it possible to write an AVStream driver using WDF? I posted this
> questions a few years back and the answer was no.
The answer has always been "yes, although it doesn't necessarily make
sense."
Many of the things that KMDF does for you are already provided by
AVStream. You wouldn't want KMDF intercepting the driver entry points,
and you can't use IoQueues because you don't usually see the IRPs. KMDF
does support a "miniport" mode, where it doesn't intercept the entry
points, so if you are comfortable with using the IoTarget concept for
sending URBs to a USB device, you can use KMDF for that.
Personally, I've never found that argument to be very compelling.
That's just a personal opinion, however.
> There were some code snippets on using AVStream with WDF in the Winhec
> 2008 presentation, and there is also some new WLP requirements for USB
> drivers to be WDF compilant.
The logo requirement does not apply to devices with isochronous pipes,
which includes almost all audio/video devices.
> So does this mean that it is now possible to use AVStream with WDF
> (since many usb audio/video device would be using AVStream driver)? If
> this is true, is there any info on what is the minimum KMDF version
> that can support this, and any info on what can and what cannot be
> done with WDF for AVStream would be appreciated.
Miniport mode has been in there since the beginning, and is described in
the documentation.
--
Tim Roberts, timr@xxxxxxxxx
Providenza & Boekelheide, Inc.
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