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Date: Thu, 30 May 2013 18:03:02 +0200
From: Laszlo Ersek <lersek@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/3] pvpanic: use FWCfgState explicitly
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To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, qemu-devel@nongnu.org, Hu Tao <hutao@cn.fujitsu.com>

On 05/30/13 17:05, Laszlo Ersek wrote:
> On 05/30/13 15:27, Michael S. Tsirkin wrote:
>> Use the type-safe FWCfgState structure instead
>> of the unsafe void *.
>>
>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>> ---
>>  hw/misc/pvpanic.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/hw/misc/pvpanic.c b/hw/misc/pvpanic.c
>> index 31e1b1d..1483f27 100644
>> --- a/hw/misc/pvpanic.c
>> +++ b/hw/misc/pvpanic.c
>> @@ -90,7 +90,7 @@ static int pvpanic_isa_initfn(ISADevice *dev)
>>  {
>>      PVPanicState *s = ISA_PVPANIC_DEVICE(dev);
>>      static bool port_configured;
>> -    void *fw_cfg;
>> +    FWCfgState *fw_cfg;
>>  
>>      memory_region_init_io(&s->io, &pvpanic_ops, s, "pvpanic", 1);
>>      isa_register_ioport(dev, &s->io, s->ioport);
>>
> 
> Doesn't this break your build? Lower down in the function there's
> 
>         fw_cfg = object_resolve_path("/machine/fw_cfg", NULL);
> 
> and object_resolve_path() returns a pointer-to-Object, not
> pointer-to-FWCfgState.

Paolo explained the guts, but don't we still need a downcast here? (No
idea how to do that nicely in the object model du jour -- maybe
OBJECT_CHECK() or similar?)

Laszlo