ARM: amba: Allow some ARM_AMBA users to compile with COMPILE_TEST

CONFIG_VFIO_AMBA has a light use of AMBA, adding some inline fallbacks
when AMBA is disabled will allow it to be compiled under COMPILE_TEST and
make VFIO easier to maintain.
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Message-Id: <3-v1-df057e0f92c3+91-vfio_arm_compile_test_jgg@nvidia.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

drivers/vfio/platform/Kconfig

@@ -12,7 +12,7 @@ config VFIO_PLATFORM
 
 config VFIO_AMBA
 	tristate "VFIO support for AMBA devices"
-	depends on VFIO_PLATFORM && ARM_AMBA
+	depends on VFIO_PLATFORM && (ARM_AMBA || COMPILE_TEST)
 	help
 	  Support for ARM AMBA devices with VFIO. This is required to make
 	  use of ARM AMBA devices present on the system using the VFIO

include/linux/amba/bus.h

@@ -105,8 +105,19 @@ extern struct bus_type amba_bustype;
 #define amba_get_drvdata(d)	dev_get_drvdata(&d->dev)
 #define amba_set_drvdata(d,p)	dev_set_drvdata(&d->dev, p)
 
+#ifdef CONFIG_ARM_AMBA
 int amba_driver_register(struct amba_driver *);
 void amba_driver_unregister(struct amba_driver *);
+#else
+static inline int amba_driver_register(struct amba_driver *drv)
+{
+	return -EINVAL;
+}
+static inline void amba_driver_unregister(struct amba_driver *drv)
+{
+}
+#endif
+
 struct amba_device *amba_device_alloc(const char *, resource_size_t, size_t);
 void amba_device_put(struct amba_device *);
 int amba_device_add(struct amba_device *, struct resource *);