Re: Being more anal about iospace accesses..

["Jörn Engel" <joern@wohnheim.fh-wedel.de>]

On Wed, 15 September 2004 10:07:29 -0700, Linus Torvalds wrote:
> On Wed, 15 Sep 2004, Jörn Engel wrote:
> > 
> > C now supports pointer arithmetic with void*?
> 
> C doesn't. gcc does. It's a documented extension, and it acts like if it 
> was done on a byte.
> 
> See gcc's user guide "Extension to the C Language Family".
> 
> It's a singularly good feature. 

Nice.

But it still leaves me confused.  Before I had this code:

	struct regs {
		uint32_t status;
		...
	}

	...

	struct regs *regs = ioremap(...);
	uint32_t status = regs->status;
	...

So now I should do it like this:

	#define REG_STATUS 0

	...

	void __iomem *regs = ioremap(...);
	uint32_t status = readl(regs + REG_STATUS);
	...

But wait, that only works when long is 32bit wide.  Plus I could be
stupid enough and "#define REG_STATUS 64" while the register space is
just 64 bytes long.  It solves the confusion about address spaces,
agreed, but overall I'm more confused now.  Hope it's just temporary.

Jörn

-- 
There is no worse hell than that provided by the regrets
for wasted opportunities.
-- Andre-Louis Moreau in Scarabouche