On Wed, Mar 08, 2017 at 06:44:47AM -0800, Guenter Roeck wrote: > On 03/07/2017 10:50 PM, Peter Chen wrote: > > > >>>>You mean type-C trigger an ACPI event, and this ACPI event can notify > >>>>related USB controller driver doing role switch? > >>> > >>>No (firmware programs the dual-role hw/registers), but never mind. > >>>That could be the case. > >>> > >>>>If it is correct, there is a notifier between type-C and USB > >>>>controller driver, how to define this notifier for non-ACPI platform? > >>> > >>>Once there is a platform with Type-C like that, the problem needs to > >>>be solved. However.. > >>> > >>>>>I'm not commenting on Roger's dual role patch series, but I don't > >>>>>really think it should be mixed with Type-C. USB Type-C and USB > >>>>>Power Delivery define their own ways of handling the roles, and they > >>>>>are not limited to the data role only. Things like OTG for example > >>>>>will, and actually can not be supported. With Type-C we will have > >>>>>competing state machines compared to OTG. The dual-role framework > >>>>>may be useful on systems that provide more traditional connectors, > >>>>>which possibly have the ID-pin like micro-AB, and possibly also > >>>>>support OTG. It can also be something that exist in parallel with the Type-C > >>class, but there just can not be any dependencies between the two. > >>>>> > >>>> > >>>>Yes, there are two independent things. But if the kernel doesn't have > >>>>a notifier between type-C message sender (type-c class) and message > >>>>receiver (like USB controller driver for role switch or other drivers > >>>>for alternate mode message), we had to find some ways at userspace. > >>> > >>>..what ever the solution is, it really can't rely on user space. > >>> > >> > >>... and, at least for our application, using extcon for the necessary notifications works > >>just fine. > >> > > > >I see, that means you have a hardware signal to notify role switch. > > > > In our case the Type-C protocol manager (including alternate mode handling) > is implemented in an EC. The EC signals the extcon-cros_ec driver, which > in turn signals the phy driver as well as the DP driver. The Type-C class > is orthogonal; extcon-cros_ec will also register with the Type-C class code > once that is upstream. > > As mentioned earlier, using extcon for signaling was the most convenient means > for us to pass events around. I am more than open to change it to a bus, > if that can be made to work - we'd have to keep in mind though that this code > already works without Type-C infrastructure and is for the most part already > upstream (the rk3399 code it ties into is upstream, and extcon-cros_ec has been > submitted as https://patchwork.kernel.org/patch/9583045/). > I am clear your implementation now, thank, Guenter. > As for to how to handle alternate mode if the Type-C protocol manager > (TCPM) is implemented in the kernel - I have not yet implemented it yet, > but my thinking goes along the line described by Heikki in his last e-mail. > > Note that we also have a kernel driver for FUSB302 which ties into my tcpm > driver. I'll have to check if that is public yet and if I or someone > else can publish it if there is interest. > > Guenter > -- Best Regards, Peter Chen -- 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
