On Mon, Nov 28, 2016 at 11:19:32AM +0100, Oliver Neukum wrote: > 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. I would be happy with module parameter. > None of that should hinder submission and inclusion. It's already there in v13. I better ping Greg already after rc1 this time, just so we don't start the review again when we are already at rc5 (and I have forgotten about this whole thing). I'll ask about the module parameter idea then, though I'm guessing he won't like it. But maybe he has some suggestions. Thanks Oliver, -- heikki -- 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
