[PATCH] ccw: split descriptor/available/used rings

["Michael S. Tsirkin" <mst@redhat.com>]

Resolves VIRTIO-23.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 virtio-v1.0-wd01-part1-specification.txt | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
index cafc34f..08cb857 100644
--- a/virtio-v1.0-wd01-part1-specification.txt
+++ b/virtio-v1.0-wd01-part1-specification.txt
@@ -1187,7 +1187,28 @@ Afterwards, CCW_CMD_SET_VQ is issued by the guest to inform the
 host about the location used for its queue. The transmitted
 structure is
 
-struct vq_info_block {
+struct vq_info_block_legacy {
+	__u64 desc;
+	__u64 avail;
+	__u64 used;
+	__u16 index;
+	__u16 num;
+	__u32 padding;
+} __attribute__ ((packed));
+
+queue contains the guest address for Descriptor Table,
+Available Ring and Used Ring for virtqueue index respectively.
+The actual virtqueue size (number of allocated buffers) is
+transmitted in num.
+padding is a reserved field, and must be set to 0.
+
+2.3.3.2.1.1 Legacy Interface: A Note on Configuring a Virtqueue
+----------------------------------
+
+When configured through the legacy interface, transitional
+devices expect CCW_CMD_SET_VQ to transfer the following structure:
+
+struct vq_info_block_legacy {
 	__u64 queue;
 	__u32 align;
 	__u16 index;
-- 
MST