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On Thu, 18 Dec 2014, Du, Changbin wrote:
> When I am checking usb remote wakeup code, I found that usb remote
> wakeup will not work after system going to S3 sate and I confirmed
> with my PC.
USB remote _does_ work.
> During enumeration, usb device will be set as wakeup capable by
> usb_set_device_state if it supports. Whether usb driver send
> SET_FEATURE(REMOTE_WAKUP) usb request when suspending on S3 depend on
> do_remote_wakeup flag which is set by choose_wakeup(). It can be
> simply presented as below.
> do_remote_wakeup = device_may_wakeup(&udev->dev);
That's right.
> The return value is always false since usb device is not marked as
> wakeup enabled(that is no one call device_set_wakeup_enable() for usb
> device). As a result, usb device will not signal wakeup event to
> host.
There's a simple solution: Call device_set_wakeup_enable() for the
device! You can do this from the command line by:
echo auto >/sys/bus/usb/devices/.../power/control
where the "..." is the pathname for your device.
> Maybe we should not allow all remote wakeup supported device can
> wakeup system by default. But for usb keyboard/mouse, I think it is
> not reasonable to disable it by default.
For USB keyboards, wakeup _is_ enabled by default. See this section of
code close to the end of usbhid_start():
/* 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);
}
> A simple way to fix this is that replace the device_may_wakeup by
> device_can_wakeup in choose_wakeup() function, just like on auto
> suspend case (usb remote wakeup works for rpm). Another way is to
> make usb device wakeup able by default. But both of them will make
> all usb devices can wakeup system. Have any better idea?
How about leaving everything the way it is now? If you want to enable
wakeup for something like a USB mouse, you can write a udev script to
do it as shown above.
Alan Stern
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