Re: [Qemu-devel] [PATCH] virtio: clarify VirtioPCIDeviceTypeInfo usage

[Eduardo Habkost]

On Wed, Apr 24, 2019 at 04:24:01PM +0100, Stefan Hajnoczi wrote:
> How to use .base_name, .generic_name, .transitional_name, and
> .non_transitional_name can be confusing.
> 
> Existing devices have .generic_name but its behavior is somewhat magic.
> 
> Devices added to new versions of the VIRTIO specification should forego
> transitional mode completely and always operate in non-transitional mode
> because there are no existing drivers for them that require backwards
> compatibility.
> 
> This patch adds comments that hopefully make it easier for developers to
> decide how to fill out VirtioPCIDeviceTypeInfo.
> 
> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>  hw/virtio/virtio-pci.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/hw/virtio/virtio-pci.h b/hw/virtio/virtio-pci.h
> index 18581854ca..debdee28b3 100644
> --- a/hw/virtio/virtio-pci.h
> +++ b/hw/virtio/virtio-pci.h
> @@ -209,7 +209,9 @@ typedef struct VirtioPCIDeviceTypeInfo {
>       * Implements both INTERFACE_PCIE_DEVICE and 
> INTERFACE_CONVENTIONAL_PCI_DEVICE,
>       * but PCI Express is supported only in non-transitional mode.
>       *
> -     * The only type implemented by QEMU 3.1 and older.
> +     * The only type implemented by QEMU 3.1 and older.  This type is less
> +     * explicit than the transitional and non-transitional device types.  Its
> +     * behavior can be affected by machine type compat properties.

I'm not sure what you mean here.  All types can be affected by
machine type compat properties when necessary, don't they?

>       */
>      const char *generic_name;
>      /*
> @@ -222,6 +224,9 @@ typedef struct VirtioPCIDeviceTypeInfo {
>       * The non-transitional device type.  Optional.
>       *
>       * Implements INTERFACE_CONVENTIONAL_PCI_DEVICE only.
> +     *
> +     * New virtio device types should only define this and base_name, thereby
> +     * allowing only non-transitional mode.
>       */
>      const char *non_transitional_name;
>  
> -- 
> 2.20.1
> 

-- 
Eduardo