virtio_config: Add virtio_config_val_len()

This patch adds virtio_config_val_len() which allows retrieving variable
length data from the virtio config space only if a specific feature is on.

Cc: Amit Shah <amit.shah@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: virtualization@lists.linux-foundation.org
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/include/linux/virtio_config.h b/include/linux/virtio_config.h
index 39c88c5..add4790 100644 (file)
--- a/include/linux/virtio_config.h
+++ b/include/linux/virtio_config.h
@@ -155,6 +155,9 @@ static inline bool virtio_has_feature(const struct virtio_device *vdev,
 #define virtio_config_val(vdev, fbit, offset, v) \
        virtio_config_buf((vdev), (fbit), (offset), (v), sizeof(*v))
 
+#define virtio_config_val_len(vdev, fbit, offset, v, len) \
+       virtio_config_buf((vdev), (fbit), (offset), (v), (len))
+
 static inline int virtio_config_buf(struct virtio_device *vdev,
                                    unsigned int fbit,
                                    unsigned int offset,