On Tue, Oct 26, 2010 at 8:05 AM, Avi Kivity <avi@xxxxxxxxxx> wrote:
> ÂOn 10/25/2010 08:38 PM, Blue Swirl wrote:
>>
>> >
>> > ÂI don't really see why we need registration; cpu_register_io() takes
>> > Âfunction pointers, a size, and an opaque, and gives an integer handle
>> > in
>> > Âreturn. ÂWith the IOPort object approach, you set up the IOPort with
>> > Âfunction pointers, size is implied, and the opaque is derived using
>> > Âcontainer_of(); the handle is simply the address of the object.
>>
>> With the handle, we can separate setting up the structures at device
>> level, and mapping the object using only the handle at bus or other
>> higher level. Can this be done with the object approach?
>
> I believe so. ÂThe handle is simply an indirect pointer, no?
Yes, but then the object should also contain size information. That
should not be needed for mapping at higher level.
>> The purpose of that patch series was to perform the separation for PCI
>> BARs. I wasn't so happy with the series, so I never pushed.
>
> In fact I think an IOPort is even more suitable; if we need additional
> attributes we can use a derived object:
>
> struct PCIIOPort {
> Â ÂIOPort ioport;
> Â Â/* additional fields */
> };
One issue with my series was that it would be great if the devices
just had some BAR structures (used by PCI layer to map the devices)
inside PCI/qdev structures, but I invented that too late. Maybe this
can be addressed in your design?
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