On 06.02.2013 21:13, Clemens Ladisch wrote:
Eldad Zack wrote:
On Tue, 5 Feb 2013, Clemens Ladisch wrote:
I thought I'd try to use implicit feedback with my simple audio device: [...] This works fine when playing something:
...
But when I then try to record at the same time, the driver refuses to configure the input endpoint (to the only format, which is already set): And despite that "alreay in use" check, the input endpoint is affected so much that playback breaks.
Is full duplex supposed to work? Does it work with other devices?
This is probably a "yes, but" :) I use my device mostly full duplex, but with jack opening both playback and capture at the same time.
I assume you are opening two different streams, one for playback and one for capture.
Jack *also* uses two different streams, but it opens them at the same time.
Can you try using jackd -d alsa -d hw:x with the device and see if that works for you?
That works. This means that there is a race condition in the driver, or that the different open/hw_params/prepare order trips it up.
I'll look for the FTU and re-try this with Eldad's latest additions once I find some time. If there are races, we should definitely fix them.
Anyway, I feel safe now to enable implicit feedback for other devices.
Nice.
On a general note, my idea from the beginning and part of the motivation to split the driver into the snd_usb_endpoint logic was to pull that class out to a separate library, so we can use it from other drivers as well. Much like what snd-usbmidi does.
There are few bits to clean up in order to remove dependencies between the endpoint code and the rest of the driver, but then your ua101 driver, snd-usb-caiaq and probably some more drivers in the future can share the generic streaming functionality.
Daniel