Re: [PATCH 1/2] add phys_addr_t for holding physical addresses

Jeremy Fitzhardinge
2008-08-11T22:15:38Z

Benjamin Herrenschmidt wrote:
> On Mon, 2008-08-11 at 12:38 -0700, Jeremy Fitzhardinge wrote:
>
>> Add a kernel-wide "phys_addr_t" which is guaranteed to be able to hold
>> any physical address. By default it equals the word size of the
>> architecture, but a 32-bit architecture can set ARCH_PHYS_ADDR_T_64BIT
>> if it needs a 64-bit phys_addr_t.
>>
>
> I've been wondering for some time why can't we make phys_addr_t and
> resource_size_t the same thing... I don't like having two ARCH_* thing
> especially since I believe the one for resources is already what we
> want.
>

I made the same argument, but Andrew thinks they're conceptually
distinct. It is theoretically possible you might have a system with >4G
memory, but all io resources < 4G, so you'd have resource_size_t
32-bits, while having 64-bit physical addresses. You can configure such
a thing, but I don't know if it's 1) useful or 2) used.

J