Messages in this thread | | | Date | Fri, 14 Mar 2008 18:45:09 +0100 (CET) | From | Roman Zippel <> | Subject | Re: [PATCH 1/4] introduce explicit signed/unsigned 64bit divide |
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Hi,
On Thu, 13 Mar 2008, Andrew Morton wrote:
> I think what happened was that [patch 3/4] fixed this up. Of course, > that patch doesn't apply on this updated [1/4]. I _could_ just take the > old [1/4] (I think), but I don't know if that wouild be bisection-friendly. > > Anyway, please redo&resend? Thanks.
Done.
> Please have a think about that code in arch/x86/kvm/i8254.c too. It is > painful to see remote subsystems (re)implementing generic infrastructure. > Can KVM use existing code? Should we hoist what KVM has done there into > generic code? Did it have to use a(nother bleeding) macro?
Looker closer at it, div64_u64() seems to be a bit overkill, as the divisor is a 32bit value, so the following should do the same job (only compile tested):
u64 muldiv64(u64 a, u32 b, u32 c) { union { u64 ll; struct { u32 low, high; }; } u, res, rl, rh;
u.ll = a; rl.ll = (u64)b * u.low; rh.ll = (u64)b * u.high; rh.ll += rl.high; res.high = div_u64_rem(rh.ll, c, &rl.high); res.low = div_u64(rl.ll, c); return res.ll; }
Moving it to a more generic location shouldn't be a big problem.
bye, Roman
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