linux-kernel - Re: USB serial regression 2.6.31.1 -> 2.6.31.2

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Date:	Sat, 10 Oct 2009 16:41:51 -0400 (EDT)
From:	Alan Stern <stern@...land.harvard.edu>
To:	Josua Dietze <digidietze@...isberghof.de>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Ben Efros <ben@...doctor.com>,
	fangxiaozhi <huananhu@...wei.com>, Greg KH <greg@...ah.com>,
	Kernel development list <linux-kernel@...r.kernel.org>,
	USB list <linux-usb@...r.kernel.org>,
	Hugh Blemings <hugh@...mings.org>
Subject: Re: USB serial regression 2.6.31.1 -> 2.6.31.2

On Sat, 10 Oct 2009, Alan Stern wrote:

> On Sat, 10 Oct 2009, Josua Dietze wrote:
...
> > This is one of the mode switching devices. It is switched to modem 
> > mode by "usb_stor_huawei_e220_init".
> > 
> > Something keeps resetting it to initial mode. It might be a 
> > powersave/suspend issue.
> 
> It's not related to powersave or suspend.  (Although both trace files
> show that the device's remote-wakeup feature did get enabled; I have no
> idea what code was responsible for doing that.  AFAIK it shouldn't
> happen unless the device is about to be suspended.)

It turns out that the remote-wakeup enable _is_ the mode-switch
command.  Don't ask me why the manufacturer decided to use an
pre-existing command to tell the device to switch modes.

Anyway, it's clear from the logs that the mode switch worked in both 
cases.  Initially the device shows only one interface, and after the 
mode switch it shows four.

Alan Stern

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