On 07.11.2012 00:54, Jeffrey Barish wrote:
I guess that snd_usb_pcm_prepare is called by the core usb system to prepare the snd driver. Anyway, snd_usb_pcm_prepare calls configure_endpoint with a substream. Then configure_endpoint calls snd_usb_endpoint_set_params with the data endpoint that corresponds to the substream. snd_usb_endpoint_set_params calls data_ep_set_params with the data ep and data_ep_set_params sets nurbs to 2 for the data endpoint.
snd_usb_endpoint_set_params has code to call sync_ep_set_params when the endpoint is type sync. sync_ep_set_params sets nurbs to 4 (why?). However, snd_usb_endpoint_set_params never invokes the call to sync_ep_set_params because ep->type is always data. Back up: snd_usb_endpoint_set_params is called from configure_endpoint. It is called from an if block contingent on the substream's having a sync endpoint. It does. However, the call to snd_usb_endpoint_set_params passes subs->data_endpoint as the first argument, so snd_usb_endpoint_set_params simply repeats the operations it performed as a result of the previous invocation. I presume that the first argument to the second call to snd_usb_endpoint_set_params should be subs->sync_endpoint.
Eh. You clearly spotted a bug here. The rally interesting thing is that that it didn't bite us earlier, as it's in since 3.6.
I made that change. Now freqm does change. However, I am getting tons of ticks. Now it sounds as if the payload size is always wrong.
Oh, 44.1 kHz works. 48 kHz works. 88.2 and 96 don't work.
That's a different issue. Would you like to prepare a patch for the issue above please?
Thanks, Daniel