[PATCH RFC incremental] virtio-pci: new PCI layout clarification

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

Here's a fixup for spec issue noted by Cornelia,
and some more clarifications on how transitional and
non transitional drivers will work.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
index 4533fac..72323ba 100644
--- a/virtio-v1.0-wd01-part1-specification.txt
+++ b/virtio-v1.0-wd01-part1-specification.txt
@@ -739,9 +739,8 @@ Transitional devices must have a Revision ID of 0.
 
 Non-transitional devices must have a Revision ID of 1.
 
-Transitional drivers must match a Revision ID of 0 or 1.
-
-Non-transitional drivers must only match a Revision ID of 1.
+Both transitional and nont-transitional drivers must match a
+Revision ID of 0 or 1.
 
 2.3.1.2. PCI Device Layout
 -------------------------
@@ -1009,6 +1008,10 @@ cfg_type
 	/* Device specific configuration */
 	#define VIRTIO_PCI_CAP_DEVICE_CFG	4
 
+	Any other value - reserved for future use. Drivers must
+	ignore any vendor-specific capability structure which has
+	a reserved cfg_type value.
+
 	More than one capability can identify the same structure - this makes it
 	possible for the device to expose multiple interfaces to drivers.  The order of
 	the capabilities in the capability list specifies the order of preference
@@ -1076,6 +1079,18 @@ notify_off_multiplier
 Legacy drivers skipped  Device Layout Detection step, assuming legacy
 configuration space in BAR0 in I/O space unconditionally.
 
+Legacy devices did not have the Virtio PCI Capability in their
+capability list.
+
+Therefore:
+
+Transitional devices should expose the Legacy Interface in I/O
+space in BAR0.
+
+Transitional drivers should look for the Virtio PCI
+Capabilities on the capability list.
+If there are not present, driver should assume a legacy device.
+
 2.3.1.3.1.1. Queue Vector Configuration
 --------------------------------------