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Date: Tue, 28 Feb 2017 16:55:33 +0100
From: Igor Mammedov <imammedo@redhat.com>
Message-ID: <20170228165533.690366cf@Igors-MacBook-Pro.local>
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Subject: Re: [Qemu-devel] [PATCH 1/4] qdev: Have qdev_set_parent_bus()
 handle devices already on a bus
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: qemu-arm@nongnu.org, qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>, Clement Deschamps <clement.deschamps@antfield.fr>, patches@linaro.org

On Tue, 28 Feb 2017 14:55:08 +0000
Peter Maydell <peter.maydell@linaro.org> wrote:

> Instead of qdev_set_parent_bus() silently doing the wrong
> thing if it's handed a device that's already on a bus,
> have it remove the device from the old bus and add it to
> the new one. This is useful for the raspi2 sdcard.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>

> ---
>  hw/core/qdev.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 06ba02e..923e626 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -102,9 +102,23 @@ static void bus_add_child(BusState *bus, DeviceState *child)
>  
>  void qdev_set_parent_bus(DeviceState *dev, BusState *bus)
>  {
> +    bool replugging = dev->parent_bus != NULL;
> +
> +    if (replugging) {
> +        /* Keep a reference to the device while it's not plugged into
> +         * any bus, to avoid it potentially evaporating when it is
> +         * dereffed in bus_remove_child().
> +         */
> +        object_ref(OBJECT(dev));
> +        bus_remove_child(dev->parent_bus, dev);
> +        object_unref(OBJECT(dev->parent_bus));
> +    }
>      dev->parent_bus = bus;
>      object_ref(OBJECT(bus));
>      bus_add_child(bus, dev);
> +    if (replugging) {
> +        object_unref(OBJECT(dev));
> +    }
>  }
>  
>  /* Create a new device.  This only initializes the device state