Hi Allan,
let me get this same thread to ask you the following
On 7/3/07, Alan Stern <[EMAIL PROTECTED]> wrote:
> On Tue, 3 Jul 2007, jidong xiao wrote:
>
> > What's the difference between event_bits and change_bits?
> > I just cannot understand why we need two variables.
> >
> >
> > 188 struct usb_hub {
> > ...
> > 205 unsigned long event_bits[1]; /* status
> > change bitmask */
> > 206 unsigned long change_bits[1]; /* ports with
> > logical connect
> > 207 status
> > change */
> >
> > Take following section for example,inside hub_events() sampled from
> > drivers/usb/core/hub.c:
> >
> > 2594 /* deal with port status changes */
> > 2595 for (i = 0; i < hub->descriptor->bNbrPorts; i++) {
> > 2596 connect_change = test_bit(i,
> > hub->change_bits);
> > 2597 if (!test_and_clear_bit(i+1,
> > hub->event_bits) &&
> > 2598 !connect_change)
> > 2599 continue;
> >
> > Why do we need to test changes_bits and then test event_bits?
>
> event_bits records which ports have their bits set in the hub's
> interrupt URB. change_bits records the ports for which we want to
> force a disable and re-enumeration.
How could I force my usb host controller to re-enumerate everything
attached on the bus through userspace?? would it be some sort of
control message???
thanks
>
> Sometimes the core needs to act as though a device has disconnected
> even when it really hasn't. That's what change_bits is for.
> event_bits, on the other hand, tells us about real connect and
> disconnect events. So the driver has to check both bit-vectors.
>
> Alan Stern
>
>
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--
Best Regards,
Felipe Balbi
[EMAIL PROTECTED]
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