Hi Alan,
> > --- a/drivers/usb/core/hub.c
> > +++ b/drivers/usb/core/hub.c
> > @@ -614,6 +614,30 @@ static int hub_ext_port_status(struct usb_hub *hub,
> int port1, int type,
> > ret = 0;
> > }
> > mutex_unlock(&hub->status_mutex);
> > +
> > + /*
> > + * There is no need to lock status_mutex here, because status_mutex
> > + * protects hub->status, and the phy driver only checks the port
> > + * status without changing the status.
> > + */
> > + if (!ret) {
> > + struct usb_device *hdev = hub->hdev;
> > +
> > + /*
> > + * Applies to roothub only. That is, when hdev->parent is
> > + * empty. Only roothub will be notified of port state
> > + * changes, since the USB PHY only cares about changes at
> > + * the next level.
> > + */
> > + if (hdev && !hdev->parent) {
>
> hdev can never be NULL, so you don't need to test it. Also, there is an
> is_root_hub() routine you can call here -- it's an inline defined in usb.h. If you
> use that then you won't have to explain it in the comment.
>
> To be fair, there are plenty of other places in the driver that test !hdev->parent
> (or !udev->parent) with no explanation.
>
Using is_root_hub() is a good choice.
Thanks,
Stanley
