Re: using DMA-API on ARM

Catalin Marinas
2014-12-05T18:31:27Z

On Fri, Dec 05, 2014 at 06:24:43PM +0000, Russell King - ARM Linux wrote:
> On Fri, Dec 05, 2014 at 05:38:39PM +0000, Catalin Marinas wrote:
> > On Fri, Dec 05, 2014 at 11:11:14AM +0000, Russell King - ARM Linux wrote:
> > > In any case, wouldn't using a u64 type for "address" be better - isn't
> > > "long long" 128-bit on 64-bit architectures?
> >
> > No, it's still 64-bit. There is no 128-bit integer in the C standard.
>
> Actually, that's a fallicy.
>
> The C99 standard (like previous versions) does not define exactly the
> number of bits in each type. It defines ranks of type, and says that
> lower ranks are a subrange of integers with higher ranks (for the same
> signed-ness.) See section 6.2.5.
>
> So, it merely states that:
>
> range(char) <= range(short) <= range(int) <= range(long) <= range(long long)

You are probably right, I haven't checked. But the ABI we use in Linux
for 64-bit, LP64, defines long long as 64-bit. Gcc has a int128_t type
but it's specific to this toolchain.

--
Catalin