On Thu, 05 Jun 2014 14:56:24 -0700
David Daney <ddaney.cavm@xxxxxxxxx> wrote:
> Evidently it is.
>
> The top of asm-generic/div64.h has:
>
> .
> .
> .
> * The semantics of do_div() are:
> *
> * uint32_t do_div(uint64_t *n, uint32_t base)
> * {
That's somewhat lacking. Does this mean that we have no consistent way
to divide a s64 number?
> .
> .
> .
>
> do_div() really passes the first parameter by reference, and C doesn't
> have by reference parameters, so the example is not quite right. But it
> does seem to imply the thing should be an *unsigned* 64-bit wide variable.
>
> It has been like this since the beginning of the git epoch.
>
> > Where is that documented.
>
> The code is the documentation.
>
> > I don't
> > see it in the comments, and I don't see anything in the Documentation
> > directory. It only states that n must be 64bit. It doesn't say unsigned
> > 64 bit.
>
> The handful of call sites I examined, seem to all use u64 or unsigned
> long long.
and u64 and unsigned long long are usually the standard type to use for
64 bits.
>
> I get:
>
> $ grep -r do_div Documentation | wc
> 0 0 0
>
> So it would seem that most of the do_div() documentation actually is the
> code.
>
Which means there isn't documentation for it.
Anyway, this probably can be safely converted to an unsigned. As I'm
not sure standard deviation can ever be negative.
-- Steve
