On Friday 30 December 2005 4:37 am, Franck wrote:
> Hi,
> 
> I'm trying to make remote wake up working on a 2.6.15-rc7 kernel and
> got a couple of questions related to that.

Note that the code paths there are in flux.  You'll likely need
to get patches now queued for 2.6.16 plus a handful I've not
yet submitted.  (Preserving some hardware workarounds involved
a saner init order for some stuff in usbcore.)


> First I noticed hc->can_wakeup that should be initialized in
> hcd->start method. It's used by core to know if the hcd support remote
> wake up, is that correct ? If so whatever its value, an attached
> device (that supports remote wakup of course) can  wake up the
> hcd...BTW, what's is the difference between hc->can_wakeup and
> hc->remote_wakeup ?

Both are going away, replaced by driver model flags that apply
to all wakeup-capable devices.  This also means that there are
two different pairs of flags associated with controllers:  the
pair for the controller itself, and a pair for the root hub.
Not all root hubs handle wakeup properly (hardware quirks), and
not all controller support it at all (board and BIOS quirks).

The difference between the flags is that one says whether the
hardware can issue wakeups; not all hardware can, though in an
ideal world it all could.  The other flag says whether it should;
again, in a non-ideal world the "can wakeup" flag isn't always
correct, and even if the device _can_ wakeup sometimes there are
prices to be paid that a user may not want to pay.


> OK, let's assume I have suspended a mouse device. If I move it, it
> wakes up the hcd. The hcd got an interrupt and in the interrupt
> handler I only raise the C_PORT_SUSPEND field in the port status
> change bits. Khubd notices this change and only asks for the root hub
> to clear the C_PORT_SUSPEND bit. Should I resume the bus when clearing
> this bit ?

It's physically impossible to have the bus suspended while some
port on it is active.  I think that answers your question.  ;)

 
> I looked at sl811's implementation but I actually don't understand how
> it works.

I'm not sure it actually does; don't use that as a model.

- Dave



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