On Tue, Jun 07, 2016 at 06:05:25PM +0300, Felipe Balbi wrote: > > Hi, > > Roger Quadros <rogerq@xxxxxx> writes: > >> I might be able to find some time to implement a proof of concept which > >> would allow your platforms to get dual-role with code we already have, > >> but I need DWC3's OTG support which, I'm assuming, you already have :-) > >> > >> If you wanna try something offline, just ping me ;-) I'll be happy to > >> help. > > > > What you are proposing is a dwc3 only solution. With the otg/dual-role > > series we are trying to be generic as much as possible. > > Well, if there is a need for that, sure. Take MUSB for instance. It > makes use of nothing of the sorts, because it doesn't have to. > Indeed, some centralized IP drivers like MUSB, chipidea, dwc3 do not need this framework for role switch. But there are some common stuffs, like OTG FSM (fully/simplified), manage roles and sysfs for role switch, these things can be in a framework, the purpose of this framework is easy for dual-role switch function. Besides, when the host and device driver are in different folders for platform, eg host/ and gadget/udc/, a role switch driver is needed if we need dual role function. Recently, the dual-role function is more and more common for USB, a framework can avoid duplicated work and let switch be standardized. > > Whether controller drivers want to use it or not is upto the driver > > maintainers but we should at least ensure that user space ABI if any, > > is consistent across different implementations. > > Role decisions should not be exposed to userspace unless as debug > feature (using e.g. DebugFS). That should be done either by the HW or > within the kernel. > > If we're discussing userspace ABI here, there's something very wrong > with OTG/DRD layer design. Currently, there are some use cases which need to switch role on the fly (will be more for type-c in future), a sysfs for role switch is necessary. -- 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
