Re: [Qemu-devel] Re: Compile files only once: some planning

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Mar 24, 2010 at 06:07:35PM -0500, Anthony Liguori wrote:
> On 03/24/2010 06:05 PM, Paul Brook wrote:
>>> On 03/24/2010 05:33 PM, Paul Brook wrote:
>>>      
>>>>> But now there is a bigger problem, how to pass the property to the
>>>>> device. It's not fair to require the user to remember to set it.
>>>>>          
>>>> It should not be a property of the device. All devices have a native
>>>> endianness (for PCI this is little-endian), and the intermediate
>>>> busses/interconnects should determine whether byteswapping occurs.
>>>>        
>>> Right, the byte swapping needs to happen at the bus level which requires
>>> that the PCI regions use a different callback mechanism (and don't
>>> register directly with the cpu).
>>>      
>> Not necessarily a different callback mechanism, but probably a different
>> registration mechanism.
>>    
>
> Problem with the current scheme is that it's tied to target_phys_addr_t.  
> It's not a target_phys_addr_t and cannot be used with functions that take 
> target_phys_addr_ts.
>
> We can either introduce a generic address type or we can introduce bus  
> specific addresses and have different callbacks.  The later has better  
> type safety and since this isn't an obvious issue to most developers,  
> that's probably an important feature.
>
> Regards,
>
> Anthony Liguori
>
>> Paul
>>    


I'd prefer a generic address type since this makes it easier to
share code: for example virtio devices can use different busses,
it's common for pci host bridges to have common code for i/o
and memory, etc.

-- 
MST