Re: [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64()

[Dan Carpenter]

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