[PATCH] pci: switch from subsystem id to device id

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

Switch virtio pci to use standard device id instead of using the
subsystem id.

As a nice side effect, this allows us to make non-transitional
devices use IDs 0x40 and up, this excludes legacy windows drivers
(which ignored the revision ID even though we told them not to)
since these match the specific subsystem ID.

And, it's probably a good idea to allow them to do this if they
want to, so there's no requirement for drivers to match all
subsystem/vendor ID configurations, but they may do so.

To avoid confusion, say "PCI Device ID" and
"PCI Subsystem ID" everywhere, prefix "PCI"
for other standard registers, for consistency.

VIRTIO-102

Note: issue reporter suggested 0x10XX where XX is the virtio
device ID. This would break all legacy drivers, historically
PCI Device ID is off by one: 0xFFF + Virtio Device ID.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 content.tex | 45 +++++++++++++++++++++++++++++++--------------
 1 file changed, 31 insertions(+), 14 deletions(-)

diff --git a/content.tex b/content.tex
index 6d6a756..da64e68 100644
--- a/content.tex
+++ b/content.tex
@@ -963,31 +963,48 @@ respectively.
 
 \subsection{PCI Device Discovery}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery}
 
-Any PCI device with Vendor ID 0x1AF4, and Device ID 0x1000 through
-0x103F inclusive is a virtio device\footnote{The actual value within this range is ignored
-}.
-
-The Subsystem Device ID indicates which virtio device is
-supported by the device, as indicated in section \ref{sec:Device Types}.
+Any PCI device with PCI Vendor ID 0x1AF4, and PCI Device ID 0x1000 through
+0x103F inclusive is a virtio device. The actual value within this range
+indicates which virtio device is supported by the device.
+The PCI Device ID is calculated by adding 0xFFF to the Virtio Device ID,
+as indicated in section \ref{sec:Device Types}.
 
 \devicenormative{\subsubsection}{PCI Device Discovery}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery}
-The Subsystem Vendor ID SHOULD reflect
-the PCI Vendor ID of the environment (it's currently only used
-for informational purposes by the driver).
 
-Non-transitional devices SHOULD have a Revision ID of 1 or higher.
+Devices MUST have the PCI Vendor ID 0x1AF4.
+Devices MUST have the PCI Device ID calculated by adding 0xFFF
+to the Virtio Device ID,
+as indicated in section \ref{sec:Device Types}.
+For example, the network card device with the Virtio Device ID 1
+has the PCI Device ID 0x1000.
+
+The PCI Subsystem Vendor ID and the PCI Subsystem Device ID MAY reflect
+the PCI Vendor and Device ID of the environment (for informational purposes by the driver).
+
+Non-transitional devices SHOULD have a PCI Revision ID of 1 or higher.
+Non-transitional devices SHOULD have a PCI Subsystem Device ID of 0x40 or higher.
 
 This is to reduce the chance of a legacy driver attempting
 to drive the device.
 
 \drivernormative{\subsubsection}{PCI Device Discovery}{Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery}
-All drivers MUST match devices with any Revision ID, this
-is to allow devices to be versioned without breaking drivers.
+Drivers MUST match devices with the PCI Vendor ID 0x1AF4 and
+the PCI Device ID calculated by adding 0xFFF to the Virtio Device ID,
+as indicated in section \ref{sec:Device Types}.
+
+Drivers MUST match devices with any Revision ID, and
+MAY match devices with any Subsystem Vendor ID and
+Subsystem Device ID, this is to allow devices to be
+versioned without breaking drivers.
 
-Drivers MUST match any Revision ID value. 
+Drivers MUST match any PCI Revision ID value.
+Drivers MAY match any PCI Subsystem Vendor ID and any
+PCI Subsystem Device ID value.
 
 \subsubsection{Legacy Interfaces: A Note on PCI Device Discovery}\label{sec:Virtio Transport Options / Virtio Over PCI Bus / PCI Device Discovery / Legacy Interfaces: A Note on PCI Device Discovery}
-Transitional devices MUST have a Revision ID of 0.
+Transitional devices MUST have a PCI Revision ID of 0.
+Transitional devices MUST have the PCI Subsystem Device ID
+matching the Virtio Device ID, as indicated in section \ref{sec:Device Types}.
 
 This is to match legacy drivers.
 
-- 
MST