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

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Date:	Sun, 11 Oct 2009 08:20:17 +1100
From:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Josua Dietze <digidietze@...isberghof.de>,
	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, 2009-10-10 at 16:41 -0400, Alan Stern wrote:
> 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.

Yes, that works, you can see the ttyUSBx ports showing up. It looks like
it may just be the resets coming from usb-storage that are breaking
things.

Cheers,
Ben.


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