On Tue, 27 Nov 2012, Bjørn Mork wrote:

Steve Glendinning [off-list ref] writes:

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Hi Bjorn,

On 27 November 2012 17:21, Steve Glendinning [off-list ref] wrote:

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Hi Bjorn,

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+     smsc75xx_set_feature(dev, USB_DEVICE_REMOTE_WAKEUP);

As mentioned in another comment to the smsc95xx driver: This is weird.
Do you really need to do that?

This is an USB interface driver.  The USB device is handled by the
generic "usb" driver, which will do the right thing.  See
drivers/usb/generic.c and drivers/usb/core/hub.c

Thanks, I've tested removing all these calls from the driver and
wakeup functionality seems to still work.

I'll resubmit my smsc75xx enhancement patchset with this change once
I've done some more testing.

Further testing shows that removing these calls stop wakeup from
system suspend working (although don't appear to impact runtime
autosuspend).  Have I missed a flag or somewhere that causes
udev->do_remote_wakeup to be set in the code you posted?

udev->do_remote_wakeup is set in choose_wakeup() in
drivers/usb/core/driver.c.  AFAICS it is always set as long as
device_may_wakeup(&udev->dev) is true.

That's right.  But is device_may_wakeup(&udev->dev) true?

By default it wouldn't be.  The normal way to set it is for the user or 
a program to do:

	echo enabled >/sys/bus/usb/devices/.../power/wakeup

Of course, a driver could disregard the user's choice and set the flag 
by itself.

Alan Stern