* Re: [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64() [not found] <20190712071746.2474-5-nishkadg.linux@gmail.com> @ 2020-04-12 13:34 ` Ivan Safonov 2020-04-14 11:56 ` Dan Carpenter 0 siblings, 1 reply; 4+ messages in thread From: Ivan Safonov @ 2020-04-12 13:34 UTC (permalink / raw) To: Nishka Dasgupta, Larry Finger, Greg Kroah-Hartman, Michael Straube, devel, linux-kernel@vger.kernel.org > 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 > - tsf = pmlmeext->TSFValue - rtw_modular64(pmlmeext->TSFValue, (pmlmeinfo->bcn_interval*1024)) - 1024; /* us */ Patch '[PATCH 01/10] staging: rtl8723bs: Remove function rtw_modular64()' have same bug. Ivan Safonov. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64() 2020-04-12 13:34 ` [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64() Ivan Safonov @ 2020-04-14 11:56 ` Dan Carpenter 2020-04-14 12:22 ` Ivan Safonov 0 siblings, 1 reply; 4+ messages in thread From: Dan Carpenter @ 2020-04-14 11:56 UTC (permalink / raw) To: Ivan Safonov Cc: Nishka Dasgupta, Larry Finger, Greg Kroah-Hartman, Michael Straube, devel, linux-kernel@vger.kernel.org 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 ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64() 2020-04-14 11:56 ` Dan Carpenter @ 2020-04-14 12:22 ` Ivan Safonov 2020-04-14 13:25 ` Dan Carpenter 0 siblings, 1 reply; 4+ messages in thread From: Ivan Safonov @ 2020-04-14 12:22 UTC (permalink / raw) To: Dan Carpenter Cc: Nishka Dasgupta, Larry Finger, Greg Kroah-Hartman, Michael Straube, devel, linux-kernel@vger.kernel.org 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. Ivan Safonov. ^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64() 2020-04-14 12:22 ` Ivan Safonov @ 2020-04-14 13:25 ` Dan Carpenter 0 siblings, 0 replies; 4+ messages in thread From: Dan Carpenter @ 2020-04-14 13:25 UTC (permalink / raw) To: Ivan Safonov Cc: devel, Greg Kroah-Hartman, linux-kernel@vger.kernel.org, Nishka Dasgupta, Larry Finger 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 ^ permalink raw reply [flat|nested] 4+ messages in thread
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2020-04-12 13:34 ` [PATCH 5/8] staging: rtl8188eu: Remove function rtw_modular64() Ivan Safonov
2020-04-14 11:56 ` Dan Carpenter
2020-04-14 12:22 ` Ivan Safonov
2020-04-14 13:25 ` Dan Carpenter
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