On 03/02/17(Fri) 12:06, Christopher Zimmermann wrote:
> [...]
> > > > > @@ -444,6 +447,11 @@ uaudio_match(struct device *parent, void
> > > > > if (uaa->iface == NULL || uaa->device == NULL)
> > > > > return (UMATCH_NONE);
> > > > >
> > > > > + if (uaa->vendor == USB_VENDOR_MAUDIO &&
> > > > > + uaa->product == USB_PRODUCT_MAUDIO_FASTTRACKPRO &&
> > > > > + uaa->configno != 2)
> > > > > + return UMATCH_NONE;
> > > >
> > > > Why to you need this?
> > >
> > > This device exposes only a very limited set of features in
> > > configuration 1.
> >
> > But configuration 1 is midi not audio right? So it won't match, so
> > why do you need that?
>
> In config 1 the device exposes these ifaces:
> 0 audio control
> 1 midi
> 2 audio play
> 3 audio rec
>
> in config 2 the device exposes these ifaces:
> 0 audio control
> 1 midi
> 2 audio analog out
> 3 audio analog / digital out
> 4 audio analog in (with mic preamps)
> 5 audio digital in
>
> if any iface in config 1 is claimed the device cannot switch to config 2.
But do you still want umidi(4) to attach or not at all?
> > > > > + if (uaa->vendor == USB_VENDOR_MAUDIO &&
> > > > > + uaa->product == USB_PRODUCT_MAUDIO_FASTTRACKPRO &&
> > > > > + uaa->configno != 2)
> > > > > return UMATCH_NONE;
> > > >
> > > > I'd leave the configno check out and add a comment explaining why
> > > > we want to force this driver to attach to uaudio(4).
> > >
> > > See my comment above about the same piece of code in uaudio.c.
> > > If I don't add this condition umidi will attach to configuration 1
> > > and configuration 2 wouldn't be tried, uaudio wouldn't attach.
> >
> > Please re-read my comment. I'm talking about the "configno" check.
> > Think about somebody reading your code in 5 years, it will just looks
> > like black magic.
>
> What about adding this comment:
>
> /*
> * This combined audio / midi device exposes its
> * full set of features only in configuration 2.
> */
Or something along the way of:
/*
* As long as the USB stack does not support switching between multiple
* configurations, only match the second one, it offers more features.
*/
> > What you're doing is working around our stupid USB detection mechanism
> > to use a specific configuration. So you don't want your device to
> > attach to umidi(4) no matter with which configuration.
> >
> > > + if (p->precision > 8)
> > > + /*
> > > + * Don't search for matching encoding.
> > > + * Just tell the upper layers which one we support.
> > > + */
> > > + p->encoding = sc->sc_alts[i].encoding;
> >
> > Why do you need that?
>
> - The audio device is big endian.
> - The uaudio driver was written for little endian devices.
> - The audio driver assumes _host_ endianness.
> - The uaudio driver will reject AUDIO_SETPAR (audio(4)) requests which don't
> exactly match the device encoding.
> - I change uaudio to communicate the supported endianness back to audio(4), so
> that userspace will receive the supported parameters via AUDIO_GETPAR and
> will use a supported encoding.
Ok I don't understand this magic, maybe ratchov@ can comment on it?
> > > + else if (p->encoding != sc->sc_alts[i].encoding)
> > > + continue;
> > > +
> > > alts_eh |= 1 << i;
> > > DPRINTFN(6,("%s: matched %s alt %d for enc/pre\n",
> > > __func__, mode == AUMODE_RECORD ? "rec" : "play", i));
>
>
>
> --
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