Feedback with embedded USB audio gadget

I see that the USB Gadget has an explicit feedback node. It seems to deliver a constant (00 00 30 00) for a sample rate of 48kHz. I see that the value is initialized to a combination of the sample rate and the "pitch", which appears to be a control of the driver. Is the pitch plumbed up to the user-level through alsa somehow (if so how)? If not, is there some ALSA layer that servos the pitch to keep the host clock and the embedded clock synchronized?