From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH RFC] virtio-pci: new config layout: using memory BAR
Date: Tue, 28 May 2013 19:43:58 +0200
Message-ID: <51A4ECDE.1020207@redhat.com>
References: <20130528160342.GA29915@redhat.com> <87bo7vvxej.fsf@codemonkey.ws>
	<20130528173257.GC30296@redhat.com>
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Cc: Peter Maydell <peter.maydell@linaro.org>,
	Anthony Liguori <aliguori@us.ibm.com>, kvm@vger.kernel.org,
	virtualization@lists.linux-foundation.org,
	Stefan Hajnoczi <stefanha@redhat.com>, Laszlo Ersek <lersek@redhat.com>,
	KONRAD Frederic <fred.konrad@greensocs.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
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Il 28/05/2013 19:32, Michael S. Tsirkin ha scritto:
>>> > > +
>>> > > +    switch (addr) {
>>> > > +    case offsetof(struct virtio_pci_common_cfg, device_feature_select):
>>> > > +        return proxy->device_feature_select;
>> > 
>> > Oh dear no...  Please use defines like the rest of QEMU.
> Any good reason not to use offsetof?

I'm not sure it's portable to use it in case labels.  IIRC, the
definition ((int)&(((T *)0)->field)) is not a valid C integer constant
expression.  Laszlo?

> I see about 138 examples in qemu.

Almost all of them are about fields in the host, not the guest, and none
of them are in case statements.

Paolo

> 
> Anyway, that's the way Rusty wrote it in the kernel header -
> I started with defines.
> If you convince Rusty to switch I can switch too,
> but I prefer reusing same structures as linux even if
> for now I've given up on reusing same headers.
> 
>