linux-kernel - Re: [34-stable regression] USB delay init quirk causes device events loss

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Message-ID: <4C8E4B14.7090904@ipom.com>
Date:	Mon, 13 Sep 2010 18:02:28 +0200
From:	Phil Dibowitz <phil@...m.com>
To:	Greg KH <gregkh@...e.de>
CC:	Alan Stern <stern@...land.harvard.edu>,
	Jiri Slaby <jslaby@...e.cz>, stable@...nel.org,
	USB list <linux-usb@...r.kernel.org>,
	Linux kernel mailing list <linux-kernel@...r.kernel.org>
Subject: Re: [34-stable regression] USB delay init quirk causes device events
 loss

On 09/13/2010 05:56 PM, Greg KH wrote:
> On Mon, Sep 13, 2010 at 11:37:49AM -0400, Alan Stern wrote:
>> On Mon, 13 Sep 2010, Jiri Slaby wrote:
>>
>>> On 09/13/2010 04:48 PM, Alan Stern wrote:
>>>> On Mon, 13 Sep 2010, Jiri Slaby wrote:
>>>>> In other words, what I could do is to add some printks into
>>>>> hub_port_connect_change if that's called at all. If you need some
>>>>> thorough debugging printks, please send me a patch to test instead.
>>>>
>>>> Hmm.  I'd prefer to explain how it's all supposed to work and let you
>>>> figure out where best to look.  Or try to debug it myself.  Does this
>>>> happen with other sorts of USB devices as well, or just wacom?
>>>
>>> With some sort of devices (I cannot reproduce myself). It's unrelated to
>>> wacom -- people with wacom were unable to even start X with this kernel.
>>> If you look at the bugreport, there are several examples:
>>> ID 046d:c517 Logitech, Inc. LX710 Cordless Desktop Laser defunct
>>> Microsoft USB keyboard defunct x Logitech mice OK
>>> 046a:0021 Cherry GmbH keyboard defunct
>>> logitech wireless laptop mouse defunct
>>> A$Tech wireless laptop mouse defunct
>>> TypeMatrix USB 2030 (ID : 1e54:2030) defunct
>>
>> Okay, I see the problem.  By moving usb_detect_quirks earlier, we end 
>> up calling usb_disable_autosuspend too soon -- before the 
>> pm_runtime_enable call in usb_new_device.  In 2.6.35 this doesn't 
>> matter because the implementation of usb_autosuspend_device has 
>> changed.
>>
>> So yes, in the end it looks like the best course is to revert this
>> patch from 2.6.34.stable.  This is unfortunate but I don't see any way
>> around it without making changes that aren't present in the current
>> kernel. For example, the pm_runtime_set_active and pm_runtime_enable
>> calls could also be moved from usb_new_device into
>> hub_port_connect_change.
> 
> Ok, I'll go revert that from the .34-stable tree and do a new release,
> as it's not nice to have a broken tree out there.

Sorry to chime in late on the conversation on my patch.

Thanks for figuring this out Alan. I think this is reasonable. However, I
think this also went into .32-stable and should probably be reverted there
as well.

I'll advise my users to make sure they have at least .35.

-- 
Phil Dibowitz                             phil@...m.com
Open Source software and tech docs        Insanity Palace of Metallica
http://www.phildev.net/                   http://www.ipom.com/

"Be who you are and say what you feel, because those who mind don't matter
 and those who matter don't mind."
 - Dr. Seuss



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