On Thu, 13 Dec 2001, David Brownell wrote: > > Unfortunately they can't keep power, if the host powers down, > > as they are buspowered. And simply call them nonresumable is an > > excuse because you don't like the remedy which is a simple clean > > device driver. > > Nope, it's a definition. Suspend/resume involves preserving > state. If they didn't keep power, they couldn't keep that state, > and they had to (re)initialize. Just like unplug/replug.
This one I don't understand - why do you claim a buspowered device couldn't keep state over suspend/resume? Suspend is quite different from power-cut as devices are still allowed to draw up to 0.5mA from the suspended USB (see 9.2.3, USB spec.). While being enough for a pm-aware microcontroler to keep its state information (like fn-address, device-config, interface alternate setting) in the microcontroler registers, it's probably insufficient to keep the firmware running or even to have an external ram powered. Hence the device _does_ keep its state, but needs to reload firmware (or parts of) on resume. And the device might simply use an eeprom to save and restore its state during suspend/resume. The required state information can be reduced to only a few bytes - which are easy to write to some eeprom during the 10ms the device may take to complete suspending. Martin _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
