[PATCH v2 RFC 1/3] virtio: add notify() callback to virtio_driver

[Heinz Graalfs <graalfs@linux.vnet.ibm.com>]

Add an optional notify() callback to virtio_driver. A backend
driver can provide this callback to perform actions for a lost
device.

notify() event values are inherited from virtio_ccw's notify()
callback. We might want to support even more of them lateron.

notify() return values are defined in include/linux/notifier.h.

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
---
 drivers/virtio/virtio.c |  9 +++++++++
 include/linux/virtio.h  | 10 ++++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index ee59b74..a7f4302 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -3,6 +3,7 @@
 #include <linux/virtio_config.h>
 #include <linux/module.h>
 #include <linux/idr.h>
+#include <linux/notifier.h>
 
 /* Unique numbering for virtio devices. */
 static DEFINE_IDA(virtio_index_ida);
@@ -186,6 +187,14 @@ void unregister_virtio_driver(struct virtio_driver *driver)
 }
 EXPORT_SYMBOL_GPL(unregister_virtio_driver);
 
+int notify_virtio_device(struct virtio_device *vdev, int event)
+{
+	struct virtio_driver *drv = drv_to_virtio(vdev->dev.driver);
+
+	return drv->notify ? drv->notify(vdev, event) : NOTIFY_DONE;
+}
+EXPORT_SYMBOL_GPL(notify_virtio_device);
+
 int register_virtio_device(struct virtio_device *dev)
 {
 	int err;
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index f15f6e7..da18e9a 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -110,6 +110,15 @@ int register_virtio_device(struct virtio_device *dev);
 void unregister_virtio_device(struct virtio_device *dev);
 
 /**
+ * notify event values
+ * @VDEV_GONE: device gone
+ */
+enum {
+	VDEV_GONE		= 1,
+};
+int notify_virtio_device(struct virtio_device *dev, int event);
+
+/**
  * virtio_driver - operations for a virtio I/O driver
  * @driver: underlying device driver (populate name and owner).
  * @id_table: the ids serviced by this driver.
@@ -129,6 +138,7 @@ struct virtio_driver {
 	void (*scan)(struct virtio_device *dev);
 	void (*remove)(struct virtio_device *dev);
 	void (*config_changed)(struct virtio_device *dev);
+	int (*notify)(struct virtio_device *dev, int event);
 #ifdef CONFIG_PM
 	int (*freeze)(struct virtio_device *dev);
 	int (*restore)(struct virtio_device *dev);
-- 
1.8.3.1