Re: [Qemu-devel] [PATCH] pci: add standard bridge device

[Avi Kivity <avi@redhat.com>]

On 09/04/2011 05:21 PM, Michael S. Tsirkin wrote:
> >  >
> >  >+static pcibus_t pci_bridge_get_size(const PCIDevice *bridge, uint8_t type)
> >  >+{
> >  >+    return pci_bridge_get_limit(bridge, type)>=
> >  >+        pci_bridge_get_base(bridge, type) ?
> >  >+        pci_bridge_get_limit(bridge, type) -
> >  >+        pci_bridge_get_base(bridge, type)  + 1 : 0;
> >  >+}
> >
> >  Correct
>
> To make sure: 0 size is ok?

Yes.

>
> >  but unreadable.
>
> variables will make it clearer.
>
> base = pci_bridge_get_base(bridge, type);
> limit = pci_bridge_get_limit(bridge, type);
> return limit>= bridge ? limit - base + 1 : 0;

So long as we're nitpicking, limit + 1 - base.

>
>
> >   Doesn't work for limit == 2^64-1, is this a
> >  possible value?
>
> You mean when base == 0?  Yes, but what can I do?
> This seems to be an API limitation of the memory API:
> memory_region_init(sec_bus->address_space_mem, "pci_pridge_pci", INT64_MAX);
> and the same for aliases: max size seems to be INT64_MAX,
> the last byte isn't covered.

Right.

> The only way to fix this would be to pass first/last instead
> of offset/size. Too late for such an API change?

Way too late.  And also won't work, since often the offset is determined 
by one party and the size by another.

> VGA I/O addresses (including ISA aliases address - AD[15::10] are not
> decoded):
> AD[9::0] = 3B0h through 3BBh and 3C0h through 3DFh

These "not decoded" bits mean you need to instantiate tons of aliases to 
implement correctly.

I plan to add core support for that eventually.


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