On Thu, 2016-11-24 at 11:57 +0200, Heikki Krogerus wrote: > On Wed, Nov 23, 2016 at 09:12:04PM -0800, Guenter Roeck wrote: > > In our implementation, the default preferred role is determined by the > > low level driver (as, in my understanding, is suggested by the standard). > > This means that the ABI will report "no preferred role", unless user space > > overwrites it, even though there _is_ in fact a preferred role, and the > > low level driver will execute try.src or try.snk based on that role. > > I'm not sure which standard are you referring? Try.SNK and Try.SRC are > optional mechanisms for *policy-based* role preference according to > the USB Type-C spec. The policy really should always come from the Not all that obvious. If you are looking at it from a distro view point if you know that you are booting on basically a gadget, you'll be happy to take the hint. And if the hardware knows it is better as a sink or source, we should take the hint. > user space in our case, but I don't think that rules out for example > initial role preferences coming from the lower level drivers. Indeed. That should not be a hindrance to submission and inclusion. > We will need a way the OS can set the initial preference for every > port. Note that once we can support that, what ever the lower level > drivers request will be overridden by it. So if for example the > platform has preference for an initial role, we will simply ignore it > if the policy says otherwise. Again, not obvious in a distro. I would actually prefer a module parameter that would allow us to prefer try.src, as we know how to be a master. None of that should hinder submission and inclusion. Regards Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
