On Tue, 21 Apr 2015, Tom Yan wrote: > I have the following two USB wireless mouse/keyboard receivers: > > logitech-djreceiver 0003:046D:C52B.0003: hiddev0,hidraw0: USB HID > v1.11 Device [Logitech USB Receiver] on usb-0000:00:14.0-13/input2 > hid-generic 0003:046D:C52E.0005: input,hidraw2: USB HID v1.11 Keyboard > [Logitech USB Receiver] on usb-0000:00:14.0-14/input0 > > The default values in their power/wakeup: > [tom@localhost ~]$ cat /sys/bus/usb/devices/3-13/power/wakeup > disabled > [tom@localhost ~]$ cat /sys/bus/usb/devices/3-14/power/wakeup > enabled > > According to https://www.kernel.org/doc/Documentation/usb/power-management.txt: > > power/wakeup > > This file is empty if the device does not support > remote wakeup. Otherwise the file contains either the > word "enabled" or the word "disabled", ... > > My question is, which part of the kernel or system determines the > default value? When I had a quick look on the source of the two driver > modules, I couldn't find any code related. So what caused the > difference? > > P.S. I have no udev rule related to power/wakeup, which is the case I > am asking about. > > [tom@localhost ~]$ cd /etc/udev/rules.d/ > [tom@localhost rules.d]$ grep wakeup * > grep: *: No such file or directory > [tom@localhost rules.d]$ cd /lib/udev/rules.d/ > [tom@localhost rules.d]$ grep wakeup * > 42-usb-hid-pm.rules:# advertise remote wakeup support but don't > actually implement > 42-usb-hid-pm.rules:# remote wakeup is working. This is from usbhid_start() in drivers/hid/usbhid/hid-core.c: /* Some keyboards don't work until their LEDs have been set. * Since BIOSes do set the LEDs, it must be safe for any device * that supports the keyboard boot protocol. * In addition, enable remote wakeup by default for all keyboard * devices supporting the boot protocol. */ if (interface->desc.bInterfaceSubClass == USB_INTERFACE_SUBCLASS_BOOT && interface->desc.bInterfaceProtocol == USB_INTERFACE_PROTOCOL_KEYBOARD) { usbhid_set_leds(hid); device_set_wakeup_enable(&dev->dev, 1); } Alan Stern -- 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
