Re: [RFC PATCH] usb/acpi: Add support usb port power off mechanism for device fixed on the motherboard

Peter Stuge
2012-05-11T14:30:27Z

Alan Stern wrote:
> > > Maybe we need an "off" setting that forces the port off?
> >
> > FWIW this would be very welcome in libusb, to do a hard reset of
> > bus-powered devices.
> >
> > It can be attempted via SET_FEATURE(PORT_POWER) to the hub, but a
> > "real" API would be nice.
>
> But remember that such an API would be very unreliable. Many hubs and
> root hubs cannot shut off port power at all, and some of the remaining
> ones use ganged power switches (you have to turn off all the ports in a
> gang before power is removed from any of them).

Yes, I know. It would be extra special nice if the kernel exposes
these various capabilities, in case they are already known.

//Peter
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