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Subject: Re: [Qemu-devel] [PATCH 17/24] arm11mpcore: use sysbus_init_mmio_cb2
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-devel@nongnu.org, kvm@vger.kernel.org

On 08/12/2011 06:23 AM, Peter Maydell wrote:
> >    static int realview_mpcore_init(SysBusDevice *dev)
> >    {
> >       mpcore_rirq_state *s = FROM_SYSBUS(mpcore_rirq_state, dev);
> >  @@ -79,7 +84,7 @@ static int realview_mpcore_init(SysBusDevice *dev)
> >           }
> >       }
> >       qdev_init_gpio_in(&dev->qdev, mpcore_rirq_set_irq, 64);
> >  -    sysbus_init_mmio_cb(dev, 0x2000, mpcore_rirq_map);
> >  +    sysbus_init_mmio_cb2(dev, mpcore_rirq_map, mpcore_rirq_unmap);
> >       return 0;
> >    }
>
> Since the mpcore code here is only using sysbus mmio callbacks as
> a way to pass things through to a sysbus mmio provided by another
> device, I think it would be cleaner to just have a way to say "my
> mmio is actually provided by this other device".
>
> For instance you could have
> MemoryRegion* sysbus_mmio_get_region(SysBusDevice *dev, int n))
> {
>      return dev->mmio[n].memory;
> }
>
> and then realview_mpcore_init() can just
>    sysbus_init_mmio_region(dev, sysbus_mmio_get_region(s->priv, 0));
>
> Or you could have a sysbus_pass_mmio() which worked like
> sysbus_pass_irq() and just said "my mmios are all this other
> device's mmios"; that's less flexible though.
>
>

Yes. Yet another option is to create a container MemoryRegion and pass 
it upwards, then allow the device that actually implements that mmio to 
register its regions with the container.

I'll leave this to the device maintainer though.

-- 
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.