On Tue, Apr 14, 2020 at 03:22:59PM +0300, Ivan Safonov wrote:
> On 4/14/20 2:56 PM, Dan Carpenter wrote:
> > On Sun, Apr 12, 2020 at 04:34:08PM +0300, Ivan Safonov wrote:
> > > > Remove function rtw_modular64 as all it does is call do_div.
> > >
> > > This is wrong. Macro do_div(x, y) change first argument x, but
> > > rtw_modular64(x, y) preserve it.
> > >
> > > > + tsf = pmlmeext->TSFValue -
> > > > do_div(pmlmeext->TSFValue, (pmlmeinfo->bcn_interval*1024)) - 1024; /*
> > > > us */
> > >
> > > rounddown(pmlmeext->TSFValue, pmlmeinfo->bcn_interval * 1024) - 1024
> > > is a better replacement for
> >
> > You're absolutely correct that the patch is buggy, but I'm not sure that
> > rounddown() is what we want.
> >
> > rtw_modular64() took the MOD of x. So it should be something like:
> >
> > tsf = pmlmeext->TSFValue - (pmlmeext->TSFValue %
> > (pmlmeinfo->bcn_interval * 1024)) - 1024; /* us */
> >
> > But what the heck is that even??? If pmlmeinfo->bcn_interval is zero
> > or one then the subtraction ends up giving us a negative.
> >
> > regards,
> > dan carpenter
> >
>
> 1. pmlmeext->TSFValue can not be negative, because it is uint64_t;
> 2. pmlmeext->TSFValue is cyclic value:
> https://en.wikipedia.org/wiki/Timing_synchronization_function ;
> 3. (rounddown(a, b)) is equal to (a - a % b) by definition.
Yeah. You're right. I got mixed up and I misread what you were
suggesting.
tsf = rounddown(pmlmeext->TSFValue, pmlmeinfo->bcn_interval * 1024) -
1024;
regards,
dan carpenter
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