Re: USB audio class - kIOAudioControlUsagePassThru implementation
Re: USB audio class - kIOAudioControlUsagePassThru implementation
- Subject: Re: USB audio class - kIOAudioControlUsagePassThru implementation
- From: Daniel Mack <email@hidden>
- Date: Thu, 20 May 2010 19:14:12 +0200
On Thu, May 20, 2010 at 09:07:03AM -0700, Brett George wrote:
> On May 12, 2010, at 1:00 AM, Daniel Mack wrote:
>
> > On Mon, May 10, 2010 at 07:38:58PM +0200, Daniel Mack wrote:
> >> I'm wondering how kIOAudioControlUsagePassThru controls are supposed to
> >> be mapped into USB audio class compliant devices. The USB audio standard
> >> (v2 in my case) does not describe this kind of control selector
> >> specifically, so I would guess the only way is to define an extension
> >> unit or to use mixer elements.
> >>
> >> The AppleUSBAudioDriver seems to do other fancy things though, and I
> >> didn't fully get my head around yet what it really looks for in the
> >> descriptors. Can anyone shed some light maybe?
> >
> > Any idea, anyone?
>
> I would recommend posting this to the USB group.
Why should they know more about an audio driver? ;)
My question is purely related to a specific feature of the USB audio
driver, not about the USB stack.
Nevermind - I just rised the question as I found a number of occurances
of 'kIOAudioControlUsagePassThru' in the USB audio driver sources,
and the code is not particularily easy to understand. But Jeff Moore
says the driver doesn't care about this kind of control at all, which
confuses me even more. So I'll need to dig thru the sources by myself,
and try to understand what's going on. Which I will do next week or so.
Thanks,
Daniel
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