Re: [PATCH RFC RESEND] ALSA: usb-audio: Scarlett mixer interface for 18i20 Gen 2

["Geoffrey D. Bennett" <g@b4.vu>]

On Wed, Apr 24, 2019 at 12:55:17PM +0200, Takashi Iwai wrote:
> On Wed, 24 Apr 2019 01:58:42 +0200,
> Geoffrey D. Bennett wrote:
> > 
> > Add mixer quirk for the Focusrite Scarlett 18i20 Gen 2 audio
> > interface. Although the interface is USB compliant, additional
> > hardware mixing, routing, and metering functionality is available
> > using proprietary USB requests.
> > 
> > Signed-off-by: Geoffrey D. Bennett <g@b4.vu>
> > ---
> > (ping resend (no changes) as no feedback received for 3 weeks)
> 
> Oh sorry, I must have overlooked the post.

No problem, thank you for your feedback.

> > - I added a private field to struct snd_usb_audio for storing the
> >   private mixer data. This seems wrong, but I didn't know where else I
> >   could/should put that data.
> 
> Hm, this is a thing I'd like to avoid as much as possible.
> Currently, each usb_mixer_elem_info may have a private pointer, and
> the original scarlett quirk uses it for storing its own "type"
> information.  This could be used for storing the data instead?
[...]

The original scarlett quirk private data is all related to each of the
mixer elements that they are attached to, but the private data I am
storing is unrelated to any specific mixer element (e.g. an
incrementing sequence number that is included in every proprietary USB
request). Do you think that I should just attach the data to the first
mixer element?

I have started work on extending the driver to support the 18i8 2nd
Gen interface as well, so I will incorporate all your feedback into
that and resend once complete.

Thanks again,
Geoffrey.