Re: [Qemu-devel] [PATCH 16/23] ioport: register ranges by byte aligned addresses always

[Avi Kivity]

On 07/25/2011 10:20 PM, Anthony Liguori wrote:
> On 07/25/2011 09:02 AM, Avi Kivity wrote:
> > The I/O port space is byte addressable, even for word and long accesses.
> >
> > An example is the VMware svga card, which has long ports on offsets 0,
> > 1, and 2.
> >
> > Signed-off-by: Avi Kivity<address@hidden>
>
> I've always thought this was odd but didn't know of a specific 
> circumstance where it broke a device.
>
> This was a big problem with the old API.  Devices don't register their 
> interest in specific sizes.  They may ignore certain size accesses but 
> that's a device specific behavior.

In fact there's on counterexample - 440FX consumes dword accesses on 
port cf8 but forwards byte and word accesses to the PCI bus.  This 
cannot be implemented with the current API (it requires the opaque to be 
equal for all word sizes).  The new API doesn't support it either; if we 
need to, we can re-issue the access but using the PCI address space 
instead of the root I/O address space.

(of course this is purely theoretical)

--
error compiling committee.c: too many arguments to function