Re: [linux-usb-devel] Re: OHCI problems with suspend/resume

[David Brownell <david-b@pacbell.net>]

Benjamin Herrenschmidt wrote:
> 
> You should look at Patrick Mochel's stuff that shall be getting in
> the official tree this month hopefully. It does that (among others)

OK, thanks for the update.  It was puzzling to see this stuff
in such a state ... I've got a few patches for USB PM that are
worth putting back in advance of that, but it seems like real
testing will need to wait until "next month".  (Tomorrow!)


> The USB "device" drivers shall just rely on the Device Model
> infrastructure to have their suspend/resume callbacks be called at the
> appropriate time. 

Yes, that's no problem.  It looks like:

   static int my_suspend(struct device *_intf, u32 state, u32 level)
   {
       struct usb_interface   *intf;
       int                    retval = 0;

       intf = to_usb_interface(_intf);
       switch (level) {
       ... cases are yet to stabilize ...
       }
       return retval;
   }

   ... similar for resume()

   static struct usb_driver my_driver {
        .owner =      THIS_MODULE,
        .name =       "MyFirstDriver",
        .probe =      my_probe,
        .disconnect = my_disconnect,
        .id_table =   my_id_table,
        .driver = {
              .suspend =    my_suspend,
              .resume =     my_resume,
         },
    };

But until the suspend()/resume() callback API stabilizes, it's
mostly useful to know that it'll be exactly that simple, and
that usbcore doesn't get in the way.


I suspect that USB should do some non-global PM stuff too.
Hub ports can be suspended when the devices connected to them
are idle for long enough ... that's not something I'd expect
system-wide PM policies to address.

- Dave