vfio: platform: introduce vfio-platform-base module

To prepare for vfio platform reset rework let's build
vfio_platform_common.c and vfio_platform_irq.c in a separate
module from vfio-platform and vfio-amba. This makes possible
to have separate module inits and works around a race between
platform driver init and vfio reset module init: that way we
make sure symbols exported by base are available when vfio-platform
driver gets probed.

The open/release being implemented in the base module, the ref
count is applied to the parent module instead.

Signed-off-by: Eric Auger <[e-mail]>
Suggested-by: Arnd Bergmann <[e-mail]>
Reviewed-by: Arnd Bergmann <[e-mail]>
Signed-off-by: Alex Williamson <[e-mail]>

drivers/vfio/platform/Makefile

···
-
-vfio-platform-y := vfio_platform.o vfio_platform_common.o vfio_platform_irq.o
+vfio-platform-base-y := vfio_platform_common.o vfio_platform_irq.o
+vfio-platform-y := vfio_platform.o
 
 obj-$(CONFIG_VFIO_PLATFORM) += vfio-platform.o
+obj-$(CONFIG_VFIO_PLATFORM) += vfio-platform-base.o
 obj-$(CONFIG_VFIO_PLATFORM) += reset/
 
 vfio-amba-y := vfio_amba.o
 
 obj-$(CONFIG_VFIO_AMBA) += vfio-amba.o
+obj-$(CONFIG_VFIO_AMBA) += vfio-platform-base.o
 obj-$(CONFIG_VFIO_AMBA) += reset/

drivers/vfio/platform/vfio_amba.c

···
 	vdev->flags = VFIO_DEVICE_FLAGS_AMBA;
 	vdev->get_resource = get_amba_resource;
 	vdev->get_irq = get_amba_irq;
+	vdev->parent_module = THIS_MODULE;
 
 	ret = vfio_platform_probe_common(vdev, &adev->dev);
 	if (ret) {

drivers/vfio/platform/vfio_platform.c

···
 	vdev->flags = VFIO_DEVICE_FLAGS_PLATFORM;
 	vdev->get_resource = get_platform_resource;
 	vdev->get_irq = get_platform_irq;
+	vdev->parent_module = THIS_MODULE;
 
 	ret = vfio_platform_probe_common(vdev, &pdev->dev);
 	if (ret)

drivers/vfio/platform/vfio_platform_common.c

···
 
 #include "vfio_platform_private.h"
 
+#define DRIVER_VERSION  "0.10"
+#define DRIVER_AUTHOR   "Antonios Motakis <[e-mail]>"
+#define DRIVER_DESC     "VFIO platform base module"
+
 static DEFINE_MUTEX(driver_lock);
 
 static const struct vfio_platform_reset_combo reset_lookup_table[] = {
···
 
 	mutex_unlock(&driver_lock);
 
-	module_put(THIS_MODULE);
+	module_put(vdev->parent_module);
 }
 
 static int vfio_platform_open(void *device_data)
···
 	struct vfio_platform_device *vdev = device_data;
 	int ret;
 
-	if (!try_module_get(THIS_MODULE))
+	if (!try_module_get(vdev->parent_module))
 		return -ENODEV;
 
 	mutex_lock(&driver_lock);
···
 	return vdev;
 }
 EXPORT_SYMBOL_GPL(vfio_platform_remove_common);
+
+MODULE_VERSION(DRIVER_VERSION);
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);

drivers/vfio/platform/vfio_platform_private.h

···
 	u32				num_irqs;
 	int				refcnt;
 	struct mutex			igate;
+	struct module			*parent_module;
 
 	/*
 	 * These fields should be filled by the bus specific binder