[PATCH RFC 1/3] virtio: add API to detect legacy devices

[Michael S. Tsirkin]

transports need to be able to detect legacy-only
devices (ATM balloon only) to use legacy path
to drive them.

Add a core API to do just that.
The implementation just blacklists balloon:
not too pretty, but let's not over-engineer.

Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
 include/linux/virtio.h  | 2 ++
 drivers/virtio/virtio.c | 6 ++++++
 2 files changed, 8 insertions(+)

diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 2bbf626..d666bcb 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -108,6 +108,8 @@ struct virtio_device {
 	void *priv;
 };
 
+bool virtio_device_is_legacy_only(struct virtio_device_id id);
+
 static inline struct virtio_device *dev_to_virtio(struct device *_dev)
 {
 	return container_of(_dev, struct virtio_device, dev);
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
index fa6b75d..6b4c1113 100644
--- a/drivers/virtio/virtio.c
+++ b/drivers/virtio/virtio.c
@@ -267,6 +267,12 @@ static struct bus_type virtio_bus = {
 	.remove = virtio_dev_remove,
 };
 
+bool virtio_device_is_legacy_only(struct virtio_device_id id)
+{
+	return id.device == VIRTIO_ID_BALLOON;
+}
+EXPORT_SYMBOL_GPL(register_virtio_driver);
+
 int register_virtio_driver(struct virtio_driver *driver)
 {
 	/* Catch this early. */
-- 
MST

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