On Fri, Jan 15, 2016 at 10:11:06AM -0500, Alan Stern wrote:
> On Fri, 15 Jan 2016, 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@xxxxxxxxxxxxx>
> >
> > Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
> >
> >
> > 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?
>
> There may not be any such cases, but there's still a good reason for
> setting the root hub's of_node pointer: to initialize the recursion
> along the USB device tree.
>
> This leaves the question of whether OF will always use the same node to
> represent the host controller and the root hub. In other words, if a
> motherboard has a fixed device plugged into a fixed root-hub port, will
> the DT description make that device a child of the host controller?
> Or will there be a node in between (to represent the root hub)?
>
I don't think we need to have such node, even root hub needs something
from device tree, it can get them from controller's node.
--
Best Regards,
Peter Chen
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