[v2,4/6] usb: roles: add API to get usb_role_switch by node

[Chunfeng Yun <chunfeng.yun@mediatek.com>]

Hi,
On Fri, 2019-03-15 at 11:26 +0200, Heikki Krogerus wrote:
> Hi Chunfeng,
> 
> On Fri, Mar 15, 2019 at 05:13:24PM +0800, Chunfeng Yun wrote:
> > I encounter a build error when CONFIG_USB_ROLE_SWITCH is not enabled,
> > 
> > drivers/usb/mtu3/mtu3_dr.o: In function `ssusb_role_sw_register':
> > ./drivers/usb/mtu3/mtu3_dr.c:460: undefined reference to
> > `usb_role_switch_register'
> > drivers/usb/mtu3/mtu3_dr.o: In function `ssusb_otg_switch_exit':
> > ./drivers/usb/mtu3/mtu3_dr.c:491: undefined reference to
> > `usb_role_switch_unregister'
> 
> So you need to add dependency on USB_ROLE_SWITCH, right?
Yes

> 
> --- a/drivers/usb/mtu3/Kconfig
> +++ b/drivers/usb/mtu3/Kconfig
> @@ -43,6 +43,7 @@ config USB_MTU3_DUAL_ROLE
>         bool "Dual Role mode"
>         depends on ((USB=y || USB=USB_MTU3) && (USB_GADGET=y || USB_GADGET=USB_MTU3))
>         depends on (EXTCON=y || EXTCON=USB_MTU3)
> +       depends on USB_ROLE_SWITCH
>         help
>           This is the default mode of working of MTU3 controller where
>           both host and gadget features are enabled.
> 
> > the following patch has fixed the issue, but seems not get into kernel,
> > [v3,08/12] usb: roles: Add usb role switch notifier.
> > https://patchwork.kernel.org/patch/10836525/
> 
> I don't understand how that fixes the problem? That patch will in any
> case be targeting v5.2. We are in the middle of merge window, so
> nothing is happening until v5.1-rc1 is tagged.
It provides some dummy inline functions when USB_ROLE_SWITCH is not
enabled, this will avoid build error

> 
> 
> thanks,
>