Re: USB rejecting sleep

[Alan Stern <stern@rowland.harvard.edu>]

On Mon, 19 Dec 2005, Benjamin Herrenschmidt wrote:

> Ok, I did a bit more tests here with a Keyspan adapter on my laptop
> (well known driver for not having the suspend/resume routines).
> 
> The good thing is with the patch, the machine goes to sleep. However,
> the device is not disconnected/reconnected. What happens it that the bus
> gets suspended anyway and the driver stays around (possibly getting
> errors on some URBs).

Yes, that's what is supposed to happen with that patch.

> This is fine, but not optimal, since that means most of the time that
> the device will not work on resume unless disconnected/reconnected. (For
> keyspan, it seems that the HW does support the suspend state, thus it's
> just a matter of closing/re-opening the port, I suppose it would be easy
> enough to fix the driver).
> 
> So this patch is good for it doesn't prevent sleep anymore, but it also
> doesn't do what we decided it should do. I think David is right that we
> should be able to disconnect the device without actually removing the
> device & driver from sysfs, just let that happen at resume time.

Of course the patch doesn't do what we talked about.  It says so right in 
the Changelog comment.

I disagree with the idea of disconnecting the device.  The right thing to 
do is what David wanted all along: unbind the driver.  This would require 
only a small change to the driver core.

It's too late for me to work on this now, but maybe tomorrow I'll have to 
a chance to write something.

Alan Stern

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