[U-Boot] [PATCH 03/23] fdt: Add resource parsing functions

[Thierry Reding]

On Tue, Aug 19, 2014 at 06:55:18AM -0600, Simon Glass wrote:
> On 19 August 2014 05:35, Thierry Reding <thierry.reding at gmail.com> wrote:
[...]
> > The Linux kernel handles this by wrapping it in an of_read_number()
> > helper and always returning u64, like this:
> >
> >         static inline u64 of_read_number(const __be32 *cell, int size)
> >         {
> >                 u64 r = 0;
> >
> >                 while (size--)
> >                         r = (r << 32) | be32_to_cpu(*(cell++));
> >
> >                 return r;
> >         }
> >
> > It obviously only works for size in { 0, 1, 2 }, but I can add a helper
> > like that if you want.
> 
> 
> That looks good. It works for the cases we need and it's obvious later
> where the logic is if we want to extend it.

This is what I have for U-Boot currently.

static fdt_addr_t fdtdec_get_address(const fdt32_t *ptr, unsigned int cells)
{
	fdt_addr_t addr = 0;

	while (cells--)
		/* do the shift in two steps to avoid warning on 32-bit */
		addr = (addr << 16) << 16 | fdt32_to_cpu(*ptr++);

	return addr;
}

I use the same function to parse the size field of reg entries, even
though the types aren't technically the same. But making the types
consistent would duplicate the above exactly, so I'm not sure it's worth
it.

Alternatively perhaps something like this could be done:

	static u64 fdtdec_get_number(const fdt32_t *ptr, unsigned int cells)
	{
		/* the above */
	}

	static fdt_addr_t fdtdec_get_address(const fdt32_t *ptr, unsigned int cells)
	{
		return fdtdec_get_number(ptr, cells);
	}

	static fdt_size_t fdtdec_get_size(const fdt32_t *ptr, unsigned int cells)
	{
		return fdtdec_get_number(ptr, cells);
	}

Again, I'm not sure it's really worth the trouble since fdt_addr_t and
fdt_size_t are both always either u32 or u64.

Thierry
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