Re: [virtio-dev] [PATCH] pci: use revision id 1 or higher for non transitional devices

[Rusty Russell <rusty@au1.ibm.com>]

"Michael S. Tsirkin" <mst@redhat.com> writes:
> VIRTIO-34
>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> ---
>  virtio-v1.0-wd01-part1-specification.txt | 12 ++++++++++--
>  1 file changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/virtio-v1.0-wd01-part1-specification.txt b/virtio-v1.0-wd01-part1-specification.txt
> index 6ab4ff8..b3f7c9e 100644
> --- a/virtio-v1.0-wd01-part1-specification.txt
> +++ b/virtio-v1.0-wd01-part1-specification.txt
> @@ -802,10 +802,18 @@ supported by the device. The Subsystem Vendor ID should reflect
>  the PCI Vendor ID of the environment (it's currently only used
>  for informational purposes by the guest).
>  
> +All Drivers must match devices with any Revision ID, this
> +is to allow devices to be versioned without breaking drivers.
> +
>  2.3.1.1.1 Legacy Interfaces: A Note on PCI Device Discovery
>  -------------------------
> -Transitional devices must also have a Revision ID of 0 to match
> -this specification.
> +Transitional devices must have a Revision ID of 0 to match
> +legacy drivers.
> +
> +Non-transitional devices must have a Revision ID of 1 or higher.
> +
> +Both transitional and non-transitional drivers must match
> +any Revision ID value.

Hmm, so a non-transitional driver should match revision ID 0?  Sure,
it'll fail gracefully when it doesn't find the capability, but it's a
bit weird.

Cheers,
Rusty.