Re: [PATCH] usb:hub set hub->change_bits when over-current happens

From: Shen Guang
Date: Tue Jan 07 2014 - 01:38:46 EST

On Tue, Jan 7, 2014 at 11:53 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> On Tue, Jan 07, 2014 at 11:35:50AM +0800, æå wrote:
>> On Tue, Jan 7, 2014 at 10:40 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>> > On Tue, Jan 07, 2014 at 10:33:14AM +0800, æå 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.


Shen Guang
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