Re: [PATCH 2/3] doc: dt-binding: generic onboard USB HUB

[Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>]

On Tue, Dec 08, 2015 at 09:24:03PM -0600, Rob Herring wrote:
> On Tue, Dec 08, 2015 at 10:58:48AM +0100, Arnd Bergmann wrote:
> > On Tuesday 08 December 2015 10:50:49 Philipp Zabel wrote:
> > > Am Dienstag, den 08.12.2015, 09:37 +0800 schrieb Peter Chen:
> > > > Add dt-binding documentation for generic onboard USB HUB.
> > > > 
> > > > Signed-off-by: Peter Chen <peter.chen-KZfg59tc24xl57MIdRCFDg@public.gmane.org>
> > > > ---
> > > >  .../bindings/usb/generic-onboard-hub.txt           | 28 ++++++++++++++++++++++
> > > >  1 file changed, 28 insertions(+)
> > > >  create mode 100644 Documentation/devicetree/bindings/usb/generic-onboard-hub.txt
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/usb/generic-onboard-hub.txt b/Documentation/devicetree/bindings/usb/generic-onboard-hub.txt
> > > > new file mode 100644
> > > > index 0000000..ea92205
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/usb/generic-onboard-hub.txt
> > > > @@ -0,0 +1,28 @@
> > > > +Generic Onboard USB HUB
> > > >+
> > > > +Required properties:
> > > > +- compatible: should be "generic-onboard-hub"
> > > 
> > > This something we don't have to define ad-hoc. The hub hangs off an USB
> > > controller, right? The "Open Firmware recommended practice: USB"
> > > document already describes how to represent USB devices in a generic
> > > manner:
> > > http://www.firmware.org/1275/bindings/usb/usb-1_0.ps
> > > 
> > > Is there a reason not to reuse this?
> > > 
> > > The usb hub node would be a child of the usb controller node, and it
> > > could use
> > > 	compatible = "usb,class9"; /* bDeviceClass 9 (Hub) */
> > 
> > Good point, I had not thought of that when I looked at the patches.
> >  
> > Yes, let's do this way. I don't know if we ever implemented the simple
> > patch to associate a USB device with a device_node, but if not, then
> > let's do it now for this driver. A lot of people have asked for it in
> > the past.
> 
> Agreed. Also, some hubs have I2C buses as well, but I still think under 
> the USB bus is the right place.
> 
> However, one complication here is often (probably this case) these 
> addtional signals need to be controlled before the device enumerates.
> 

Yes, I did not find a way to let the USB bus code handle it, so I had to
write a platform driver to do it

-- 

Best Regards,
Peter Chen
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