* drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
@ 2022-12-23 10:54 Dan Carpenter
2022-12-24 16:19 ` Andy Shevchenko
0 siblings, 1 reply; 8+ messages in thread
From: Dan Carpenter @ 2022-12-23 10:54 UTC (permalink / raw)
To: oe-kbuild, Qingtao Cao
Cc: lkp, oe-kbuild-all, linux-kernel, Bartosz Golaszewski,
Andy Shevchenko
tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
config: ia64-randconfig-m031-20221218
compiler: ia64-linux-gcc (GCC) 12.1.0
If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
smatch warnings:
drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
vim +52 drivers/gpio/gpio-exar.c
696868d0a79c21 Bartosz Golaszewski 2020-09-30 47 static unsigned int
696868d0a79c21 Bartosz Golaszewski 2020-09-30 48 exar_offset_to_sel_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
696868d0a79c21 Bartosz Golaszewski 2020-09-30 49 {
5134272f9f3f71 Qingtao Cao 2022-09-02 50 unsigned int pin = exar_gpio->first_pin + (offset % 16);
5134272f9f3f71 Qingtao Cao 2022-09-02 51 unsigned int cascaded = offset / 16;
5134272f9f3f71 Qingtao Cao 2022-09-02 @52 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
Why not change this to pin > 8 instead. Comparisons are faster than
divide ops. Way more readable too.
5134272f9f3f71 Qingtao Cao 2022-09-02 53
5134272f9f3f71 Qingtao Cao 2022-09-02 54 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
696868d0a79c21 Bartosz Golaszewski 2020-09-30 55 }
696868d0a79c21 Bartosz Golaszewski 2020-09-30 56
696868d0a79c21 Bartosz Golaszewski 2020-09-30 57 static unsigned int
696868d0a79c21 Bartosz Golaszewski 2020-09-30 58 exar_offset_to_lvl_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
696868d0a79c21 Bartosz Golaszewski 2020-09-30 59 {
5134272f9f3f71 Qingtao Cao 2022-09-02 60 unsigned int pin = exar_gpio->first_pin + (offset % 16);
5134272f9f3f71 Qingtao Cao 2022-09-02 61 unsigned int cascaded = offset / 16;
5134272f9f3f71 Qingtao Cao 2022-09-02 @62 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
5134272f9f3f71 Qingtao Cao 2022-09-02 63
5134272f9f3f71 Qingtao Cao 2022-09-02 64 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
696868d0a79c21 Bartosz Golaszewski 2020-09-30 65 }
--
0-DAY CI Kernel Test Service
https://01.org/lkp
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-23 10:54 drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8' Dan Carpenter
@ 2022-12-24 16:19 ` Andy Shevchenko
2022-12-24 19:30 ` Dan Carpenter
0 siblings, 1 reply; 8+ messages in thread
From: Andy Shevchenko @ 2022-12-24 16:19 UTC (permalink / raw)
To: Dan Carpenter
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
Lähetetty iPhonesta
> Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
>
> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
> commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
> config: ia64-randconfig-m031-20221218
> compiler: ia64-linux-gcc (GCC) 12.1.0
>
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <error27@gmail.com>
>
> smatch warnings:
> drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
>
I don’t think this is a good advice. If we want to limit that, we need to check also upper limit. But. The GPIO framework does that. So, changing / to >= is bogus.
> vim +52 drivers/gpio/gpio-exar.c
>
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 47 static unsigned int
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 48 exar_offset_to_sel_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 49 {
> 5134272f9f3f71 Qingtao Cao 2022-09-02 50 unsigned int pin = exar_gpio->first_pin + (offset % 16);
> 5134272f9f3f71 Qingtao Cao 2022-09-02 51 unsigned int cascaded = offset / 16;
> 5134272f9f3f71 Qingtao Cao 2022-09-02 @52 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
>
> Why not change this to pin > 8 instead. Comparisons are faster than
> divide ops. Way more readable too.
>
> 5134272f9f3f71 Qingtao Cao 2022-09-02 53
> 5134272f9f3f71 Qingtao Cao 2022-09-02 54 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 55 }
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 56
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 57 static unsigned int
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 58 exar_offset_to_lvl_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 59 {
> 5134272f9f3f71 Qingtao Cao 2022-09-02 60 unsigned int pin = exar_gpio->first_pin + (offset % 16);
> 5134272f9f3f71 Qingtao Cao 2022-09-02 61 unsigned int cascaded = offset / 16;
> 5134272f9f3f71 Qingtao Cao 2022-09-02 @62 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
> 5134272f9f3f71 Qingtao Cao 2022-09-02 63
> 5134272f9f3f71 Qingtao Cao 2022-09-02 64 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 65 }
>
> --
> 0-DAY CI Kernel Test Service
> https://01.org/lkp
>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-24 16:19 ` Andy Shevchenko
@ 2022-12-24 19:30 ` Dan Carpenter
2022-12-24 19:36 ` Dan Carpenter
2022-12-25 11:45 ` Andy Shevchenko
0 siblings, 2 replies; 8+ messages in thread
From: Dan Carpenter @ 2022-12-24 19:30 UTC (permalink / raw)
To: Andy Shevchenko
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
On Sat, Dec 24, 2022 at 05:19:27PM +0100, Andy Shevchenko wrote:
>
>
> Lähetetty iPhonesta
>
> > Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
> >
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
> > commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
> > config: ia64-randconfig-m031-20221218
> > compiler: ia64-linux-gcc (GCC) 12.1.0
> >
> > If you fix the issue, kindly add following tag where applicable
> > | Reported-by: kernel test robot <lkp@intel.com>
> > | Reported-by: Dan Carpenter <error27@gmail.com>
> >
> > smatch warnings:
> > drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> > drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> >
>
>
>
> I don’t think this is a good advice. If we want to limit that, we need
> to check also upper limit. But. The GPIO framework does that. So,
> changing / to >= is bogus.
How is checking pin / 8 not mathematically equivalent to pin >= 8?
I don't understand this code at all. The divide is inscrutable Is it
storing something in in the lower 3 bits and something in bit 4? In
that case it might be nicer to just check (pin & BIT(4)).
regards,
dan carpenter
>
>
> > vim +52 drivers/gpio/gpio-exar.c
> >
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 47 static unsigned int
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 48 exar_offset_to_sel_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 49 {
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 50 unsigned int pin = exar_gpio->first_pin + (offset % 16);
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 51 unsigned int cascaded = offset / 16;
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 @52 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
> >
> > Why not change this to pin > 8 instead. Comparisons are faster than
> > divide ops. Way more readable too.
> >
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 53
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 54 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 55 }
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 56
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 57 static unsigned int
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 58 exar_offset_to_lvl_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 59 {
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 60 unsigned int pin = exar_gpio->first_pin + (offset % 16);
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 61 unsigned int cascaded = offset / 16;
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 @62 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 63
> > 5134272f9f3f71 Qingtao Cao 2022-09-02 64 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
> > 696868d0a79c21 Bartosz Golaszewski 2020-09-30 65 }
> >
> > --
> > 0-DAY CI Kernel Test Service
> > https://01.org/lkp
> >
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-24 19:30 ` Dan Carpenter
@ 2022-12-24 19:36 ` Dan Carpenter
2022-12-25 11:45 ` Andy Shevchenko
1 sibling, 0 replies; 8+ messages in thread
From: Dan Carpenter @ 2022-12-24 19:36 UTC (permalink / raw)
To: Andy Shevchenko
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
On Sat, Dec 24, 2022 at 10:30:39PM +0300, Dan Carpenter wrote:
> On Sat, Dec 24, 2022 at 05:19:27PM +0100, Andy Shevchenko wrote:
> >
> >
> > Lähetetty iPhonesta
> >
> > > Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
> > >
> > > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> > > head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
> > > commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
> > > config: ia64-randconfig-m031-20221218
> > > compiler: ia64-linux-gcc (GCC) 12.1.0
> > >
> > > If you fix the issue, kindly add following tag where applicable
> > > | Reported-by: kernel test robot <lkp@intel.com>
> > > | Reported-by: Dan Carpenter <error27@gmail.com>
> > >
> > > smatch warnings:
> > > drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> > > drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> > >
> >
> >
> >
> > I don’t think this is a good advice. If we want to limit that, we need
> > to check also upper limit. But. The GPIO framework does that. So,
> > changing / to >= is bogus.
>
>
> How is checking pin / 8 not mathematically equivalent to pin >= 8?
>
> I don't understand this code at all. The divide is inscrutable Is it
> storing something in in the lower 3 bits and something in bit 4? In
> that case it might be nicer to just check (pin & BIT(4)).
>
Or a macro which does:
#define GET_UPPER_BIT_THING(pin) ((pin >> 8) & 0xMASK)
regards,
dan carpenter
^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-24 19:30 ` Dan Carpenter
2022-12-24 19:36 ` Dan Carpenter
@ 2022-12-25 11:45 ` Andy Shevchenko
2022-12-25 11:50 ` Andy Shevchenko
1 sibling, 1 reply; 8+ messages in thread
From: Andy Shevchenko @ 2022-12-25 11:45 UTC (permalink / raw)
To: Dan Carpenter
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
Lähetetty iPhonesta
> Dan Carpenter <error27@gmail.com> kirjoitti 24.12.2022 kello 20.30:
>
>> On Sat, Dec 24, 2022 at 05:19:27PM +0100, Andy Shevchenko wrote:
>>
>>
>> Lähetetty iPhonesta
>>
>>> Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
>>>
>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>>> head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
>>> commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
>>> config: ia64-randconfig-m031-20221218
>>> compiler: ia64-linux-gcc (GCC) 12.1.0
>>>
>>> If you fix the issue, kindly add following tag where applicable
>>> | Reported-by: kernel test robot <lkp@intel.com>
>>> | Reported-by: Dan Carpenter <error27@gmail.com>
>>>
>>> smatch warnings:
>>> drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
>>> drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
>>>
>>
>>
>>
>> I don’t think this is a good advice. If we want to limit that, we need
>> to check also upper limit. But. The GPIO framework does that. So,
>> changing / to >= is bogus.
>
>
> How is checking pin / 8 not mathematically equivalent to pin >= 8?
The point is that semantically the / is better in case this code will ever support more than two banks of pins.
> I don't understand this code at all. The divide is inscrutable Is it
> storing something in in the lower 3 bits and something in bit 4? In
> that case it might be nicer to just check (pin & BIT(4)).
>
> regards,
> dan carpenter
>
>>
>>
>>> vim +52 drivers/gpio/gpio-exar.c
>>>
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 47 static unsigned int
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 48 exar_offset_to_sel_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 49 {
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 50 unsigned int pin = exar_gpio->first_pin + (offset % 16);
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 51 unsigned int cascaded = offset / 16;
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 @52 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
>>>
>>> Why not change this to pin > 8 instead. Comparisons are faster than
>>> divide ops. Way more readable too.
>>>
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 53
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 54 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 55 }
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 56
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 57 static unsigned int
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 58 exar_offset_to_lvl_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 59 {
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 60 unsigned int pin = exar_gpio->first_pin + (offset % 16);
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 61 unsigned int cascaded = offset / 16;
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 @62 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 63
>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 64 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 65 }
>>>
>>> --
>>> 0-DAY CI Kernel Test Service
>>> https://01.org/lkp
>>>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-25 11:45 ` Andy Shevchenko
@ 2022-12-25 11:50 ` Andy Shevchenko
2022-12-27 17:46 ` Dan Carpenter
0 siblings, 1 reply; 8+ messages in thread
From: Andy Shevchenko @ 2022-12-25 11:50 UTC (permalink / raw)
To: Dan Carpenter
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
Lähetetty iPhonesta
> Andy Shevchenko <andy.shevchenko@gmail.com> kirjoitti 25.12.2022 kello 12.45:
>
>
>
> Lähetetty iPhonesta
>
>>> Dan Carpenter <error27@gmail.com> kirjoitti 24.12.2022 kello 20.30:
>>>
>>> On Sat, Dec 24, 2022 at 05:19:27PM +0100, Andy Shevchenko wrote:
>>>
>>>
>>> Lähetetty iPhonesta
>>>
>>>> Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
>>>>
>>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
>>>> head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
>>>> commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
>>>> config: ia64-randconfig-m031-20221218
>>>> compiler: ia64-linux-gcc (GCC) 12.1.0
>>>>
>>>> If you fix the issue, kindly add following tag where applicable
>>>> | Reported-by: kernel test robot <lkp@intel.com>
>>>> | Reported-by: Dan Carpenter <error27@gmail.com>
>>>>
>>>> smatch warnings:
>>>> drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
>>>> drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
>>>>
>>>
>>>
>>>
>>> I don’t think this is a good advice. If we want to limit that, we need
>>> to check also upper limit. But. The GPIO framework does that. So,
>>> changing / to >= is bogus.
>>
>>
>> How is checking pin / 8 not mathematically equivalent to pin >= 8?
>
> The point is that semantically the / is better in case this code will ever support more than two banks of pins.
On top of that it’s paired with pin % 8.
>
>> I don't understand this code at all. The divide is inscrutable Is it
>> storing something in in the lower 3 bits and something in bit 4? In
>> that case it might be nicer to just check (pin & BIT(4)).
>>
>> regards,
>> dan carpenter
>>
>>>
>>>
>>>> vim +52 drivers/gpio/gpio-exar.c
>>>>
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 47 static unsigned int
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 48 exar_offset_to_sel_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 49 {
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 50 unsigned int pin = exar_gpio->first_pin + (offset % 16);
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 51 unsigned int cascaded = offset / 16;
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 @52 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOSEL_HI : EXAR_OFFSET_MPIOSEL_LO;
>>>>
>>>> Why not change this to pin > 8 instead. Comparisons are faster than
>>>> divide ops. Way more readable too.
>>>>
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 53
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 54 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 55 }
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 56
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 57 static unsigned int
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 58 exar_offset_to_lvl_addr(struct exar_gpio_chip *exar_gpio, unsigned int offset)
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 59 {
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 60 unsigned int pin = exar_gpio->first_pin + (offset % 16);
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 61 unsigned int cascaded = offset / 16;
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 @62 unsigned int addr = pin / 8 ? EXAR_OFFSET_MPIOLVL_HI : EXAR_OFFSET_MPIOLVL_LO;
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 63
>>>> 5134272f9f3f71 Qingtao Cao 2022-09-02 64 return addr + (cascaded ? exar_gpio->cascaded_offset : 0);
>>>> 696868d0a79c21 Bartosz Golaszewski 2020-09-30 65 }
>>>>
>>>> --
>>>> 0-DAY CI Kernel Test Service
>>>> https://01.org/lkp
>>>>
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-25 11:50 ` Andy Shevchenko
@ 2022-12-27 17:46 ` Dan Carpenter
2022-12-27 18:30 ` Andy Shevchenko
0 siblings, 1 reply; 8+ messages in thread
From: Dan Carpenter @ 2022-12-27 17:46 UTC (permalink / raw)
To: Andy Shevchenko
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
On Sun, Dec 25, 2022 at 12:50:46PM +0100, Andy Shevchenko wrote:
>
>
> Lähetetty iPhonesta
>
> > Andy Shevchenko <andy.shevchenko@gmail.com> kirjoitti 25.12.2022 kello 12.45:
> >
> >
> >
> > Lähetetty iPhonesta
> >
> >>> Dan Carpenter <error27@gmail.com> kirjoitti 24.12.2022 kello 20.30:
> >>>
> >>> On Sat, Dec 24, 2022 at 05:19:27PM +0100, Andy Shevchenko wrote:
> >>>
> >>>
> >>> Lähetetty iPhonesta
> >>>
> >>>> Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
> >>>>
> >>>> tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> >>>> head: f9ff5644bcc04221bae56f922122f2b7f5d24d62
> >>>> commit: 5134272f9f3f71d4e1f3aa15cb09321af49b3646 gpio: exar: access MPIO registers on cascaded chips
> >>>> config: ia64-randconfig-m031-20221218
> >>>> compiler: ia64-linux-gcc (GCC) 12.1.0
> >>>>
> >>>> If you fix the issue, kindly add following tag where applicable
> >>>> | Reported-by: kernel test robot <lkp@intel.com>
> >>>> | Reported-by: Dan Carpenter <error27@gmail.com>
> >>>>
> >>>> smatch warnings:
> >>>> drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> >>>> drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> >>>>
> >>>
> >>>
> >>>
> >>> I don’t think this is a good advice. If we want to limit that, we need
> >>> to check also upper limit. But. The GPIO framework does that. So,
> >>> changing / to >= is bogus.
> >>
> >>
> >> How is checking pin / 8 not mathematically equivalent to pin >= 8?
> >
> > The point is that semantically the / is better in case this code will ever support more than two banks of pins.
>
> On top of that it’s paired with pin % 8.
>
I noticed that, but it's a common bug though that a lot of people
accidentally write if (pin / 8) when if ((pin % 8) == 0) is intended.
For example:
drivers/rtc/rtc-m48t59.c
132 M48T59_WRITE((bin2bcd(tm->tm_mon + 1) & 0x1F), M48T59_MONTH);
133 M48T59_WRITE(bin2bcd(year % 100), M48T59_YEAR);
134
135 if (pdata->type == M48T59RTC_TYPE_M48T59 && (year / 100))
^^^^^^^^^^
This code is pretty clearly an example of where people accidentally uses
/ to mean "divides cleanly". (I have not patched or reported this code,
btw so if anyone wants an easy patch to send it's available).
136 val = (M48T59_WDAY_CEB | M48T59_WDAY_CB);
137 val |= (bin2bcd(tm->tm_wday) & 0x07);
138 M48T59_WRITE(val, M48T59_WDAY);
regards,
dan carpenter
^ permalink raw reply [flat|nested] 8+ messages in thread* Re: drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
2022-12-27 17:46 ` Dan Carpenter
@ 2022-12-27 18:30 ` Andy Shevchenko
0 siblings, 0 replies; 8+ messages in thread
From: Andy Shevchenko @ 2022-12-27 18:30 UTC (permalink / raw)
To: Dan Carpenter
Cc: oe-kbuild, Qingtao Cao, lkp, oe-kbuild-all, linux-kernel,
Bartosz Golaszewski
On Tue, Dec 27, 2022 at 7:46 PM Dan Carpenter <error27@gmail.com> wrote:
> On Sun, Dec 25, 2022 at 12:50:46PM +0100, Andy Shevchenko wrote:
> > > Andy Shevchenko <andy.shevchenko@gmail.com> kirjoitti 25.12.2022 kello 12.45:
> > >>> Dan Carpenter <error27@gmail.com> kirjoitti 24.12.2022 kello 20.30:
> > >>> On Sat, Dec 24, 2022 at 05:19:27PM +0100, Andy Shevchenko wrote:
> > >>>> Dan Carpenter <error27@gmail.com> kirjoitti 23.12.2022 kello 11.54:
...
> > >>>> smatch warnings:
> > >>>> drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> > >>>> drivers/gpio/gpio-exar.c:62 exar_offset_to_lvl_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8'
> > >>>
> > >>> I don’t think this is a good advice. If we want to limit that, we need
> > >>> to check also upper limit. But. The GPIO framework does that. So,
> > >>> changing / to >= is bogus.
> > >>
> > >> How is checking pin / 8 not mathematically equivalent to pin >= 8?
> > >
> > > The point is that semantically the / is better in case this code will ever support more than two banks of pins.
> >
> > On top of that it’s paired with pin % 8.
>
> I noticed that, but it's a common bug though that a lot of people
> accidentally write if (pin / 8) when if ((pin % 8) == 0) is intended.
Probably. Here the pin/8 is the correct approach, it shows the bank
number, where each bank is out of 8 pins.
> For example:
Thanks, but it's unrelated to this case.
--
With Best Regards,
Andy Shevchenko
^ permalink raw reply [flat|nested] 8+ messages in thread
end of thread, other threads:[~2022-12-27 18:31 UTC | newest]
Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-12-23 10:54 drivers/gpio/gpio-exar.c:52 exar_offset_to_sel_addr() warn: replace divide condition 'pin / 8' with 'pin >= 8' Dan Carpenter
2022-12-24 16:19 ` Andy Shevchenko
2022-12-24 19:30 ` Dan Carpenter
2022-12-24 19:36 ` Dan Carpenter
2022-12-25 11:45 ` Andy Shevchenko
2022-12-25 11:50 ` Andy Shevchenko
2022-12-27 17:46 ` Dan Carpenter
2022-12-27 18:30 ` Andy Shevchenko
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