AppleUSBAudio reads GET_MAX volume, won't change range on status interrupt
AppleUSBAudio reads GET_MAX volume, won't change range on status interrupt
- Subject: AppleUSBAudio reads GET_MAX volume, won't change range on status interrupt
- From: Dominik Peklo <email@hidden>
- Date: Mon, 31 Jan 2011 06:49:59 -0800 (PST)
Dear Alison,
My USB Audio 1.0 device has a feature unit with volume control. I've set up status interrupt endpoint notifying host of device originated volume changes. Observing traffic with USB bus analyzer, I can see that upon raising interrupt pointing to the feature unit, Mac OS X issues all the GET_CUR, GET_MIN, GET_MAX & GET_RES requests. However, even if I report modified GET_MAX value, the volume control range does not change and remains at the value initially reported during enumeration. You might ask why would I need to change the range on-the-fly - the device has two user selectable means of volume control, both with a different maximum gain. Is there anything I can do on the device side to make this work or should I just file a bug report?
Best Regards,
Dominik
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