Implicit feedback on BOSS GT-1, the saga continues...

[Lucas]

I wholeheartedly agree with everything you wrote, Mike.  Takashi is the
person who knows best how to implement these changes, and is definitely the
most capable.  I will get back to you about retesting my other Roland
devices with this trick, although I only have a few of the many devices I'd
ultimately like this solution implemented for.  Also, I haven't noticed the
sync-related clicking with the other devices I own, but I'm confident they
won't be hurt by the change.  I'll let you both know, though, when I get
around to testing them.

Thanks as ever,

  Lucas

On Fri, Apr 9, 2021 at 11:47 AM Mike Oliphant <oliphant at nostatic.org> wrote:

> Hi Lucas,
>
> Your observation that the Roland D-05 still needs the capture feedback
> made me try some more testing, and I think the GT-1 actually is the same.
>
> I use my device with jackd running for both capture/playback at the same
> time. This works for me without capture feedback enabled. But, it turns out
> that just doing an "arecord" without playback fails. Enabling the capture
> feedback makes capture also work without playback (and everything else
> still works perfectly).
>
> Given this, I agree that it seems likely that most, if not all, of these
> Roland devices work the same way. It would be great to get more devices
> tested, though.
>
> As to an actual patch, I think it is probably best left to Takashi to
> decide if he is comfortable with making a change to
> snd_usb_endpoint_start() in endpoint.c, and if so, how he wants to make it
> conditional for devices - whether an ID check in endpoint.c, or a flag on
> feedback setup, or some other way.
>
> Mike
>