Hi Igor,

please don't remove the alsa ML from Cc:.

On 11.03.2013 09:37, Igor Levin wrote:

[...]

But now we got a bit of a breather and our developers are finally able to give Linux the attention it deserves to get it going. I have couple fundamental question which you guys can help us with:

1. Does Linux audio support the Implicit feedback mode where the Out

pipe will source the same amount of samples as are coming into related IN pipe.

Yes.

This is the sync mode we use in Orion 32. If this is so, could you kindly provide the file/line number in the source code where we can see how it makes the packetising decision.

Please have a look at sound/usb/endpoint.c - this is where the packet logic lives in. Please read the comments in this file - the packet sending for this implicit feedback mode is implemented in queue_pending_output_urbs().

2. We are upgrading our Zodiac DAC to use asynchronous feedback mode.

What Async feedback mode formats does Linux support? Where can we see it in the source?

Linux supports feedback over dedicated isochronous endpoints as well. The format is auto-detected in snd_usb_handle_sync_urb(), also in sound/usb/endpoint.c, after each stream start. Internally, the driver uses Q16.16.

Hope this helps. In case of more specific questions, please just let me know.

Thanks, Daniel