> For usb hid devices: No idea how they work and whenever we can put them > into sleep somehow (with/without guest cooperation).
The issue with USB is that it is (by design) a polled system. The UHCI adapter has to wakeup every 1ms to read transfer descriptors from guest RAM. Until recently there was a bug in the UHCI emulation that would wake the guest even if the tablet NACKed the poll. See http://lists.nongnu.org/archive/html/qemu-devel/2010-04/msg00150.html USB does support "autosuspend". This allows a guest to put a device to sleep, and have it wake up when something interesting happens. In theory this includes HID devices. However I believe linux disables it because there's so much broken hardware out there that implements it incorrectly. I suspect qemu does not currently implement this feature either. Paul
