virtio: simplify config mechanism.
Previously we used a type/len pair within the config space, but this
seems overkill. We now simply define a structure which represents the
layout in the config space: the config space can now only be extended
at the end.
The main driver-visible changes:
1) We indicate what fields are present with an explicit feature bit.
2) Virtqueues are explicitly numbered, and not in the config space.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
diff --git a/include/linux/lguest_launcher.h b/include/linux/lguest_launcher.h
index 697104d..589be3e 100644
--- a/include/linux/lguest_launcher.h
+++ b/include/linux/lguest_launcher.h
@@ -23,7 +23,12 @@
struct lguest_device_desc {
/* The device type: console, network, disk etc. Type 0 terminates. */
__u8 type;
- /* The number of bytes of the config array. */
+ /* The number of virtqueues (first in config array) */
+ __u8 num_vq;
+ /* The number of bytes of feature bits. Multiply by 2: one for host
+ * features and one for guest acknowledgements. */
+ __u8 feature_len;
+ /* The number of bytes of the config array after virtqueues. */
__u8 config_len;
/* A status byte, written by the Guest. */
__u8 status;
@@ -31,7 +36,7 @@
};
/*D:135 This is how we expect the device configuration field for a virtqueue
- * (type VIRTIO_CONFIG_F_VIRTQUEUE) to be laid out: */
+ * to be laid out in config space. */
struct lguest_vqconfig {
/* The number of entries in the virtio_ring */
__u16 num;