I'd still call that a bug myself. The solution would appear to be that drivers should be able to tell the kernel "I can't let you go into deep sleep right now"

I'd still call that a bug myself. The solution would appear to be that drivers should be able to tell the kernel "I can't let you go into deep sleep right now" when they're active. Say when the USB camera is actually capturing video, when it isn't it should be perfectly fine to let it go into the deep states. A hard drive or something else bulk like that is certainly a different beast altogether. So at least maybe preventing the deep sleep when something in isochronous mode is transmitting data should be fine, (I understand this makes the assumption that USB cameras are sane and drop the isochronous mode when not doing video, I don't know if this is a good assumption).