Keith A. Milner wrote: > I'm struggling to understand why the code is behaving as it does in > practice Because the code has evolved over a long time, and it tries to handle not only both versions of the USB audio specification, but also devices as they are behaving in practice. > My observation when plugging the USB device in is that, as expected, it tries > to build the audio device, and add components to it including attaching > capture and playback streams. It seems to go through this phase without too > many surprises, and we get to the standard dmesg output: > > usbcore: registered new interface driver snd-usb-audio > > After this, it gets confusing. > > It seems to open and close the PCMs That happens due to requests from user space, probably PulseAudio. > kernel: [ 1987.452947] usb 1-1: Unable to change format on ep #8e: already in use So this is a Roland device? Playback-synchronized-to-capture is a very special case; at the moment, nobody understands this code completely. But the problem for this device might be that it requires some vendor-specific messages to enable it in the first place. Regards, Clemens _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
