On Tue, Jan 7, 2014 at 10:40 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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.
Then hub_events() will ignore this change, below is a code fragment of
hub_events()
/* deal with port status changes */
for (i = 1; i <= hub->descriptor->bNbrPorts; i++) {
if (test_bit(i, hub->busy_bits))
continue;
connect_change = test_bit(i, hub->change_bits);
wakeup_change = test_and_clear_bit(i, hub->wakeup_bits);
if (!test_and_clear_bit(i, hub->event_bits) &&
!connect_change && !wakeup_change)
continue;
According to spec, software need to disable the port if there is an
over-current condition, while current code will not, since it will not
detect such condition.
but if we disable CONFIG_USB_SUSPEND, software can detect the
over-current condition. I am still checking the code to get the
reason.
--
Shen Guang
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