Re: [PATCH 01/14] ARM: LPC32XX: Initial architecture header files

[Russell King - ARM Linux <linux@arm.linux.org.uk>]

On Tue, Feb 09, 2010 at 05:52:23PM +0100, Uwe Kleine-König wrote:
> [Added linux-sparse@vger.kernel.org to Cc:]
> 
> On Tue, Feb 09, 2010 at 09:59:34AM +0000, Russell King - ARM Linux wrote:
> > On Tue, Feb 09, 2010 at 10:31:29AM +0100, Uwe Kleine-König wrote:
> > > > +#define io_p2v(x)	((void __iomem *) (unsigned long) IO_ADDRESS(x))
> > > Is this cast to unsigned long needed?  AFAIK IO_ADDRESS(x) has
> > > type unsigned for x in { 0x0 ... 0xffffffff } (provided that int uses a
> > > 32 bit 2s-complement representation).  If unsigned long is really
> > > needed, maybe put it into the IO_ADDRESS macro?
> > 
> > int -> void __iomem * = sparse warning
> > unsigned long -> void __iomem * = no sparse warning
> Ah, OK, I see.  But IMHO it's a poor reason to add the cast.  Either
> the cast is necessary/recommended or sparse is wrong.  In the first case
> the reasoning shouldn't have to do with sparse, in the latter sparse
> should be fixed.

The point is that on 64-bit architectures, a pointer may be representable
by an unsigned long, but not an int.

> Is this intended?  What is the preferred way to define iomem pointers?

Define a numerical address with a UL suffix is the simplest way.
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