[PATCH] usb: hide usb_of_get_companion_dev for CONFIG_USB=n

[Arnd Bergmann]

The renesas UDC implementation now calls usb_of_get_companion_dev(),
which is only defined when CONFIG_USB is enabled:

drivers/usb/gadget/udc/renesas_usb3.o: In function `renesas_usb3_probe':
renesas_usb3.c:(.text+0xa34): undefined reference to `usb_of_get_companion_dev'

To avoid the build error, we need two changes:

- usb_of_get_companion_dev must be stubbed out when CONFIG_USB is
  disabled, so it the udc driver can be built for a gadget-only
  mode kernel
- With CONFIG_USB=m, we must not attempt to have USB_RENESAS_USB3
  built-in, so we need a soft dependency on USB.

Fixes: 39facfa01c9f ("usb: gadget: udc: renesas_usb3: Add register of usb role 
switch")
Signed-off-by: Arnd Bergmann <a...@arndb.de>
---
 drivers/usb/gadget/udc/Kconfig | 1 +
 include/linux/usb/of.h         | 6 +++++-
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/gadget/udc/Kconfig b/drivers/usb/gadget/udc/Kconfig
index 0a16cbd4e528..663a8bd67a7b 100644
--- a/drivers/usb/gadget/udc/Kconfig
+++ b/drivers/usb/gadget/udc/Kconfig
@@ -193,6 +193,7 @@ config USB_RENESAS_USB3
        tristate 'Renesas USB3.0 Peripheral controller'
        depends on ARCH_RENESAS || COMPILE_TEST
        depends on EXTCON
+       depends on USB || !USB
        select USB_ROLE_SWITCH
        help
           Renesas USB3.0 Peripheral controller is a USB peripheral controller
diff --git a/include/linux/usb/of.h b/include/linux/usb/of.h
index dba55ccb9b53..733339218466 100644
--- a/include/linux/usb/of.h
+++ b/include/linux/usb/of.h
@@ -23,7 +23,6 @@ struct device_node *usb_of_get_device_node(struct usb_device 
*hub, int port1);
 bool usb_of_has_combined_node(struct usb_device *udev);
 struct device_node *usb_of_get_interface_node(struct usb_device *udev,
                u8 config, u8 ifnum);
-struct device *usb_of_get_companion_dev(struct device *dev);
 #else
 static inline enum usb_dr_mode
 of_usb_get_dr_mode_by_phy(struct device_node *np, int arg0)
@@ -53,6 +52,11 @@ usb_of_get_interface_node(struct usb_device *udev, u8 
config, u8 ifnum)
 {
        return NULL;
 }
+#endif
+
+#if IS_ENABLED(CONFIG_OF) && IS_ENABLED(CONFIG_USB)
+struct device *usb_of_get_companion_dev(struct device *dev);
+#else
 static inline struct device *usb_of_get_companion_dev(struct device *dev)
 {
        return NULL;
-- 
2.18.0