Re: [Qemu-devel] [PATCH v2 06/17] sysbus: add sysbus_pass_mmio

[Peter Maydell]

On 4 June 2013 13:13, Paolo Bonzini <address@hidden> wrote:
> This matches sysbus_pass_irq in cases where a device is a thin wrapper
> of another.  MMIO regions will keep the subdevice as the owner.
>
> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  hw/core/sysbus.c     | 12 ++++++++++++
>  hw/cpu/arm11mpcore.c |  2 +-
>  include/hw/sysbus.h  |  1 +
>  3 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/hw/core/sysbus.c b/hw/core/sysbus.c
> index 9004d8c..6dbd1f8 100644
> --- a/hw/core/sysbus.c
> +++ b/hw/core/sysbus.c
> @@ -117,6 +117,18 @@ void sysbus_init_mmio(SysBusDevice *dev, MemoryRegion 
> *memory)
>      dev->mmio[n].memory = memory;
>  }
>
> +/* Pass MMIOs from a target device.  */
> +void sysbus_pass_mmio(SysBusDevice *dev, SysBusDevice *target)
> +{
> +    int i;
> +    assert(dev->num_mmio == 0);
> +    dev->num_mmio = target->num_mmio;
> +    for (i = 0; i < dev->num_mmio; i++) {
> +        assert(target->mmio[i].addr == -1);
> +        dev->mmio[i] = target->mmio[i];
> +    }
> +}

This is much less flexible than just using sysbus_mmio_get_region(),
because it only lets you pass the whole set of MMIOs from the
other device through, not just the ones you want. Please
just make reference counting work properly with passing
MemoryRegion*s around.

-- PMM