Re: [Qemu-devel] [PATCH v4 06/16] net: Remove vlan qdev property

[Stefan Hajnoczi <stefanha@gmail.com>]

On Mon, Jun 4, 2012 at 6:29 AM,  <zwu.kernel@gmail.com> wrote:
> From: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
>
> The vlan feature is implemented using hubs and no longer uses
> special-purpose VLANState structs that are accessible as qdev
> properties.
>
> Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> ---
>  hw/qdev-properties.c |   72 --------------------------------------------------
>  hw/qdev.c            |    2 -
>  hw/qdev.h            |    4 ---
>  net.h                |    3 --
>  4 files changed, 0 insertions(+), 81 deletions(-)

This commit looks suspicious because it removes a user-visible qdev
property but we're trying to preserve backward compatibility.  This
command-line will break:

x86_64-softmmu/qemu-system-x86_64 -net user,vlan=1 -device virtio-net-pci,vlan=1

Instead of dropping the qdev_prop_vlan completely the
hw/qdev-properties.c code needs to call net/hub.h external functions
to implement equivalent functionality:

1. Setting the vlan=<id> property looks up the hub port and assigns
the NICConf->peer field.
2. Getting the vlan property looks up the hub id (i.e. vlan id) given
the peer.  If the peer is not a hub port the result is -1.

When I wrote this patch I missed the big picture and forgot about
backwards compatibility :(.

Do you feel comfortable rewriting this commit?

Stefan