Re: [PATCH -next] usb: gadget: Add dependency for USB_TEGRA_XUDC

[Thierry Reding]

On Mon, Nov 04, 2019 at 10:59:45AM +0800, Mao Wenan wrote:
> If CONFIG_USB_TEGRA_XUDC=y and CONFIG_USB_ROLE_SWITCH=m,
> below erros can be seen:
> drivers/usb/gadget/udc/tegra-xudc.o: In function `tegra_xudc_remove':
> tegra-xudc.c:(.text+0x6b0): undefined reference to `usb_role_switch_unregister'
> drivers/usb/gadget/udc/tegra-xudc.o: In function `tegra_xudc_probe':
> tegra-xudc.c:(.text+0x1b88): undefined reference to `usb_role_switch_register'
> drivers/usb/gadget/udc/tegra-xudc.o: In function `tegra_xudc_usb_role_sw_work':
> tegra-xudc.c:(.text+0x5ecc): undefined reference to `usb_role_switch_get_role'
> 
> This patch add dependency USB_ROLE_SWITCH for UDC driver.
> 
> Fixes: 49db427232fe ("usb: gadget: Add UDC driver for tegra XUSB device mode controller")
> Signed-off-by: Mao Wenan <maowenan@xxxxxxxxxx>
> ---
>  drivers/usb/gadget/udc/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/usb/gadget/udc/Kconfig b/drivers/usb/gadget/udc/Kconfig
> index acaec3a..d103154 100644
> --- a/drivers/usb/gadget/udc/Kconfig
> +++ b/drivers/usb/gadget/udc/Kconfig
> @@ -445,6 +445,7 @@ config USB_TEGRA_XUDC
>  	tristate "NVIDIA Tegra Superspeed USB 3.0 Device Controller"
>  	depends on ARCH_TEGRA || COMPILE_TEST
>  	depends on PHY_TEGRA_XUSB
> +	depends on USB_ROLE_SWITCH

It looks like most other drivers that use the USB role switch class do
"select" here. Now, that's suboptimal because USB_ROLE_SWITCH is a user-
visible symbol, which can lead to conflicts, so it should be avoided. I
think that in this case it might make sense to hide USB_ROLE_SWITCH and
then convert all "depends on USB_ROLE_SWITCH" occurrences to "select
USB_ROLE_SWITCH". The USB role switch class is, after all, not useful by
itself. It always needs a host and/or gadget driver to make use of it.

Thierry

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