Re: [RFC][PATCH 2/3] usb: roles: Add usb role switch notifier.

[Hans de Goede]

Hi,

On 18-10-2019 21:53, John Stultz wrote:
> On Fri, Oct 18, 2019 at 12:30 PM Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
> > Looking at drivers/usb/typec/tcpm/tcpci.c: tcpci_set_vconn I see that
> > there is a data struct with vendor specific callbacks and that the
> > drivers/usb/typec/tcpm/tcpci_rt1711h.c implements that.
> >
> > So you may want something similar here. But things are tricky here,
> > because when nothing is connected you want to provide Vbus for
> > the USB-A ports, which means that if someone then connects a
> > USB-A to C cable to connect the board to a PC (switching the port
> > to device mode) there will be a time when both sides are supplying
> > 5V if I remember the schedule correctly.
>
> Ok. Thanks for the pointer, I'll take a look at that to see if I can
> get it to work.
>
> > I think that the original hack might not be that bad, the whole hw
> > design seems so, erm, broken, that you probably cannot do proper
> > roleswapping anyways.  So just tying Vbus to host mode might be
> > fine, the question then becomes again how can some other piece
> > of code listen to the role-switch events...
>
> So, at least in the current approach (see the v3 series), I've
> basically set the hub driver as an role-switch intermediary, sitting
> between the calls from the tcpm to the dwc3 driver. It actually works
> better then the earlier notifier method (which had some issues with
> reliably establishing the initial state on boot).  Does that approach
> work for you?

That sounds like it might be a nice solution. But I have not seen the
code, I think I was not Cc-ed on v3. Do you have a patchwork or
lore.kernel.org link for me?

Regards,

Hans