Re: [PATCH V2 3/4] usb: Bind devices to ACPI devices when possible

Alan Stern
2012-03-14T14:44:44Z

On Wed, 14 Mar 2012, Greg KH wrote:

> On Wed, Mar 14, 2012 at 12:48:11PM +0000, Matthew Garrett wrote:
> > On Wed, Mar 14, 2012 at 09:20:44AM +0800, Lan Tianyu wrote:
> > > On 2012年03月13日 05:45, Matthew Garrett wrote:
> > > >Built-in USB devices will typically have a representation in the system
> > > >ACPI tables. Add support for binding the two together so the USB code can
> > > >make use of the associated methods.
> > > hi Matthew:
> > > acpi glue framework only can cover situation that the port has been
> > > connected with some device. so without device, no acpi handle can be used to
> > > access "UPC" and "PLD".
> > > Whether the usb port is user-visible or not is also useful when there
> > > is no device. For example, if it is known that the usb port is not user-visible
> > > and connectable. The usb hub port can be power-off.
> > > So usb/acpi binding should consider those usb ports without plugging device.
> > > Does this make sense? :)
> >
> > I agree that this woud be useful, but right now we don't have port
> > objects so there's nowhere to expose this. Greg, do you have any
> > feelings about how this coud be handled?
>
> If you wanted to do something like this, you are right, you would need
> to create a "port" device and put it on every hub. Odds are that's
> probably not worth it as you will be adding more indirection on every
> USB device, yet only ACPI based systems would be able to do anything
> with them.

Even on ACPI systems, most host controllers are not able to power off
individual ports.

Alan Stern

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