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

[Paolo Bonzini]

Il 09/06/2012 05:04, Zhi Yong Wu ha scritto:
>>>> 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 :(.
>>>>
> To be honest, i am concerned if anyone uses this syntax. Since the
> feature will finally be discarded, i suggest that we don't support
> this now. If someone complains this later, we can fix it. If nobody
> complains, that is what we hope.

I think you're missing the big picture of this series, which is exactly
_not_ to discard the VLAN feature, but just to rewrite it in a better way.

That said, I agree that this is a somewhat fringe usage; most people
will use -net nic,model=virtio,vlan=1 rather than "-device".  We may get
by with dropping it.  I have no strong opinion either way.

Paolo