Re: [PATCH 0/3] Globally defining phys_addr_t

From: Ralf Baechle
Date: Mon Sep 15 2008 - 04:00:09 EST

On Thu, Sep 11, 2008 at 12:03:36PM +0200, Geert Uytterhoeven wrote:

> On Thu, 11 Sep 2008, Jeremy Fitzhardinge wrote:
> > This is a repost of a little 3-patch series which Andrew has been
> > carrying in -mm. It cleans up the definition of phys_addr_t to make it
> > kernel-wide rather than x86-specific, and fixes up PFN_PHYS() to use it
> > to avoid address truncation.
> >
> > We currently have a few workarounds for this problem in the tree, but
> > Alex found another bug caused by PFN_PHYS(), so it's probably better if
> > you bring these patches into tip.git for now.
> >
> > PowerPC also defines a phys_addr_t with the same meaning as x86; the
> > powerpc arch maintainers are happy with these patches.
> If I'm not mistaking, this is also true for some MIPS machines.

Jeremy probably missed it because it's called phys_t on MIPS. It's usually
the same size as unsigned long but a few of the 32-bit Alchemy SOCs have
peripherals placed outside of the 32-bit physical address space so for
those CONFIG_64BIT_PHYS_ADDR will be defined and phys_t be unsigned long
long and used for some pagetable stuff to map those devices into the 32-bit
virtual address space.

UM uses a phys_t for its pagetables.

A single data type for everybody is enough. phys_addr_t or phys_t I don't
care; I went for phys_t because it's shorter, less to type.

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