Re: [PATCH v3 1/1] USB: core: let USB device know device node

Peter Chen
2016-01-18T07:42:18Z

On Fri, Jan 15, 2016 at 12:11:27PM +0100, Arnd Bergmann wrote:
> On Friday 15 January 2016 17:17:27 Peter Chen wrote:
> > Although most of USB devices are hot-plug's, there are still some devices
> > are hard wired on the board, eg, for HSIC and SSIC interface USB devices.
> > If these kinds of USB devices are multiple functions, and they can supply
> > other interfaces like i2c, gpios for other devices, we may need to
> > describe these at device tree.
> >
> > In this commit, it uses "reg" in dts as port number to match the port
> > number decided by USB core, if they are the same, then the device node
> > is for the device we are creating for USB core.
> >
> > Signed-off-by: Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
>
> Acked-by: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
>
>
> Just one last question:
>
> > dev->active_duration = -jiffies;
> > #endif
> > - if (root_hub) /* Root hub always ok [and always wired] */
> > + if (root_hub) { /* Root hub always ok [and always wired] */
> > dev->authorized = 1;
> > - else {
> > + dev->of_node = bus->controller->of_node;
>
>
> You are adding the of_node of the controller to the root hub, which I
> guess means that we now have two 'struct device' instances with the
> same of_node. They have different bus_types, so I think that is ok,
> but I wonder if it would be better to leave out the of_node for the
> root hub to avoid the confusion. Can you think of a case where we
> actually want to add properties for the root hub that we can't do
> more easily in the host controller?
>

When the 1st level USB device (non-roothub device) is created, it's parent is
root hub, but not controller from the USB bus view.

For simply, the root hub is almost the same with controller, and
the controller is at platform bus, but the root hub is at USB bus.

--

Best Regards,
Peter Chen