On Wed, Aug 4, 2010 at 10:49 PM, Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > On Wed, 4 Aug 2010, Xiaofan Chen wrote: > >> The reason I would like to use a refresh is to wake up the device >> without opening it again. > > Why? And if you do want to wake up a device, what's wrong with opening > it? Could the device go asleep after being opened? If yes, maybe refresh the descriptor is a cheap way to wake up the device if it can be achieved. >> >Under Linux, a suspended device will be woken up as soon as >> > libusb opens the device file. >> >> Then why libusb caches the descriptors if avoiding to wake up a >> sleeping device is the goal? > > I don't know. Are the descriptors cached even while the device file > isn't open? Probably Daniel and others can help answer the question. Maybe the goal of caching the descriptors (after opening the device) is not to save energy after all. -- Xiaofan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
