Re: [PATCH v10 2/7] usb: mux: add generic code for dual role port mux

Peter Chen
2016-06-06T02:10:53Z

On Sun, Jun 05, 2016 at 04:46:55PM +0800, Lu Baolu wrote:
> Hi,
>
> On 06/05/2016 04:33 PM, Jun Li wrote:
> >> Port mux is part of dual role switch, but not the whole thing.
> >> >
> >> > Dual role switch includes at least below things:
> >> > - ID or type-C event detection
> >> > - port mux
> >> > - VBUS management
> >> > - start/stop host/device controllers
> >> >
> >> > An OTG/Dual-role framework can be used to keep all these things run
> >> > together with an internal state machine. But it's not duplicated with a
> >> > generic framework for port mux and the port mux drivers.
> >> >
> >>> > > Your
> >>> > > case is just like Renesas case, which uses two different drivers
> >>> > > between peripheral and host[1].
> >> >
> >> > In my case, the port mux devices are physical devices and they can be
> >> > controlled through GPIO pins or device registers. They are independent of
> >> > both peripheral and host controllers.
> >> >
> > I also think current OTG/Dual role framework can support your case, if you
> > find there is any limitation of it which can't meet your requirement, we
> > should improve it, Roger also provide an example of dual role switch with
> > USB3 based on his OTG core.
>
> Why do we need an OTG framework to support a device driver?

Just like you said above, OTG framework can manage role switch, the
role switch may need to start or stop host/gadget driver according to
different hardware signals or user input.

> Is it something like a bus or class driver?

The DRD/OTG framework uses the same device structure with the caller,
the caller can be a dual-role controller driver (like dwc3, chipidea,
etc), or a separate switch driver which like your mux port driver.

--

Best Regards,
Peter Chen