usb_get_max_power
if (usb_get_max_power(udev, c) > udev->bus_mA) {
delta = usb_get_max_power(udev, udev->actconfig);
i = dev->bus_mA - usb_get_max_power(dev, cp);
rc = sysfs_emit(buf, "%dmA\n", usb_get_max_power(udev, actconfig));