linux-kernel - Re: [PATCH] usb:hub set hub->change

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Message-ID: <CANthSfZGP1zHd2kog04DT6GO_0NrkyLuAm=oGpKWmQC+onYUBA@mail.gmail.com>
Date:	Tue, 7 Jan 2014 14:38:36 +0800
From:	Shen Guang <shenguang10@...il.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb:hub set hub->change_bits when over-current happens

On Tue, Jan 7, 2014 at 11:53 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
> On Tue, Jan 07, 2014 at 11:35:50AM +0800, 沈光 wrote:
>> On Tue, Jan 7, 2014 at 10:40 AM, Greg KH <gregkh@...uxfoundation.org> wrote:
>> > On Tue, Jan 07, 2014 at 10:33:14AM +0800, 沈光 wrote:
>> >> set hub->change_bits when we plug in a device which causes
>> >> over-current condition, so that hub_events() will check it.
>> >
>> > Why?
>> >
>> > What does this solve?  Is this a bug with existing devices that needs to
>> > be backported to older kernels?
>> >
>> > thanks,
>> >
>> > greg k-h
>>
>> This is something that we found when we are doing compliance test with xHCI.
>> If we enable CONFIG_USB_SUSPEND, and plug in a bad device which causes
>> over-current condition to the root port, the hub->change_bits will not
>> be set in current code in the function of hub_activate.
>
> Now that's something that should go in the changelog, don't you think?
>
> thanks,
>
> greg k-h

Sure, I agree.
I am sorry I didn't make it clear enough.
And the reason why over-current can be detected if CONFIG_USB_SUSPEND
is disabled, is that the interrupt pipe of the hub will report the
change and set hub->event_bits, and then hub_events() will check what
events happened.

Thanks,

Shen Guang
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