[PATCH] hwmon: emc2103: use min_t() for explicit type in fan target clamp

[PATCH] hwmon: emc2103: use min_t() for explicit type in fan target clamp

[Animesh Rai]

Using min() with an explicit cast on one operand is fragile. Replace
with min_t(u16, ...) to make the intended comparison type explicit and
avoid implicit type conversion.

Signed-off-by: Animesh Rai <animeshrai853@gmail.com>
---
 drivers/hwmon/emc2103.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
index 27dc149a3ed9..fbb1b4025eb7 100644
--- a/drivers/hwmon/emc2103.c
+++ b/drivers/hwmon/emc2103.c
@@ -348,7 +348,7 @@ static ssize_t fan1_div_store(struct device *dev, struct device_attribute *da,
 	/* update fan target if high byte is not disabled */
 	if ((data->fan_target & 0x1fe0) != 0x1fe0) {
 		u16 new_target = (data->fan_target * old_div) / new_div;
-		data->fan_target = min(new_target, (u16)0x1fff);
+		data->fan_target = min_t(u16, new_target, 0x1fff);
 		write_fan_target_to_i2c(client, data->fan_target);
 	}
 
-- 
2.43.0

Re: [PATCH] hwmon: emc2103: use min_t() for explicit type in fan target clamp

[Guenter Roeck]

On 7/6/26 09:25, Animesh Rai wrote:
> Using min() with an explicit cast on one operand is fragile. Replace
> with min_t(u16, ...) to make the intended comparison type explicit and
> avoid implicit type conversion.
> 

Sorry, I have no idea what you are trying to fix here. Both parameters
are u16. There is nothing "fragile" about that.

Guenter

> Signed-off-by: Animesh Rai <animeshrai853@gmail.com>
> ---
>   drivers/hwmon/emc2103.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
> index 27dc149a3ed9..fbb1b4025eb7 100644
> --- a/drivers/hwmon/emc2103.c
> +++ b/drivers/hwmon/emc2103.c
> @@ -348,7 +348,7 @@ static ssize_t fan1_div_store(struct device *dev, struct device_attribute *da,
>   	/* update fan target if high byte is not disabled */
>   	if ((data->fan_target & 0x1fe0) != 0x1fe0) {
>   		u16 new_target = (data->fan_target * old_div) / new_div;
> -		data->fan_target = min(new_target, (u16)0x1fff);
> +		data->fan_target = min_t(u16, new_target, 0x1fff);
>   		write_fan_target_to_i2c(client, data->fan_target);
>   	}
>   

Re: [PATCH] hwmon: emc2103: use min_t() for explicit type in fan target clamp

[David Laight]

On Mon,  6 Jul 2026 21:55:19 +0530
Animesh Rai <animeshrai853@gmail.com> wrote:

> Using min() with an explicit cast on one operand is fragile. Replace
> with min_t(u16, ...) to make the intended comparison type explicit and
> avoid implicit type conversion.

min_t() is worse than having a cast on the argument to min().
It just casts both arguments to the specified type.
If you'd tried you's have found you could have just deleted the cast.
But why is new_target u16, it could just be 'unsigned int'.
That saves a load of masking instructions.
Were old_div 9 and new_div 1 the rescale could overflow 16 bits,
overflowing 32 is much less likely.
(The surrounding code may make the overflow impossible...)

If the code even right?
It ignores values 0x1fe0 to 0x1fff (assuming the high bits can't
be set) so they must be 'special' in some way, but doesn't stop the
same 'special' values being generated when rescaled.

	David

> 
> Signed-off-by: Animesh Rai <animeshrai853@gmail.com>
> ---
>  drivers/hwmon/emc2103.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
> index 27dc149a3ed9..fbb1b4025eb7 100644
> --- a/drivers/hwmon/emc2103.c
> +++ b/drivers/hwmon/emc2103.c
> @@ -348,7 +348,7 @@ static ssize_t fan1_div_store(struct device *dev, struct device_attribute *da,
>  	/* update fan target if high byte is not disabled */
>  	if ((data->fan_target & 0x1fe0) != 0x1fe0) {
>  		u16 new_target = (data->fan_target * old_div) / new_div;
> -		data->fan_target = min(new_target, (u16)0x1fff);
> +		data->fan_target = min_t(u16, new_target, 0x1fff);
>  		write_fan_target_to_i2c(client, data->fan_target);
>  	}
>  

Re: [PATCH] hwmon: emc2103: use min_t() for explicit type in fan target clamp

[Animesh Rai]

Sorry for the noise, I misread the types, the operand was already u16
and the cast was unnecessary. I once again apologize for wasting your
time and disturbing you.


On Tue, Jul 7, 2026 at 1:27 AM David Laight
<david.laight.linux@gmail.com> wrote:
>
> On Mon,  6 Jul 2026 21:55:19 +0530
> Animesh Rai <animeshrai853@gmail.com> wrote:
>
> > Using min() with an explicit cast on one operand is fragile. Replace
> > with min_t(u16, ...) to make the intended comparison type explicit and
> > avoid implicit type conversion.
>
> min_t() is worse than having a cast on the argument to min().
> It just casts both arguments to the specified type.
> If you'd tried you's have found you could have just deleted the cast.
> But why is new_target u16, it could just be 'unsigned int'.
> That saves a load of masking instructions.
> Were old_div 9 and new_div 1 the rescale could overflow 16 bits,
> overflowing 32 is much less likely.
> (The surrounding code may make the overflow impossible...)
>
> If the code even right?
> It ignores values 0x1fe0 to 0x1fff (assuming the high bits can't
> be set) so they must be 'special' in some way, but doesn't stop the
> same 'special' values being generated when rescaled.
>
>         David
>
> >
> > Signed-off-by: Animesh Rai <animeshrai853@gmail.com>
> > ---
> >  drivers/hwmon/emc2103.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/hwmon/emc2103.c b/drivers/hwmon/emc2103.c
> > index 27dc149a3ed9..fbb1b4025eb7 100644
> > --- a/drivers/hwmon/emc2103.c
> > +++ b/drivers/hwmon/emc2103.c
> > @@ -348,7 +348,7 @@ static ssize_t fan1_div_store(struct device *dev, struct device_attribute *da,
> >       /* update fan target if high byte is not disabled */
> >       if ((data->fan_target & 0x1fe0) != 0x1fe0) {
> >               u16 new_target = (data->fan_target * old_div) / new_div;
> > -             data->fan_target = min(new_target, (u16)0x1fff);
> > +             data->fan_target = min_t(u16, new_target, 0x1fff);
> >               write_fan_target_to_i2c(client, data->fan_target);
> >       }
> >
>

Re: [PATCH] hwmon: emc2103: use min_t() for explicit type in fan target clamp

[Guenter Roeck]

On 7/6/26 12:57, David Laight wrote:
> On Mon,  6 Jul 2026 21:55:19 +0530
> Animesh Rai <animeshrai853@gmail.com> wrote:
> 
>> Using min() with an explicit cast on one operand is fragile. Replace
>> with min_t(u16, ...) to make the intended comparison type explicit and
>> avoid implicit type conversion.
> 
> min_t() is worse than having a cast on the argument to min().
> It just casts both arguments to the specified type.
> If you'd tried you's have found you could have just deleted the cast.
> But why is new_target u16, it could just be 'unsigned int'.
> That saves a load of masking instructions.
> Were old_div 9 and new_div 1 the rescale could overflow 16 bits,
> overflowing 32 is much less likely.
> (The surrounding code may make the overflow impossible...)
> 
> If the code even right?
> It ignores values 0x1fe0 to 0x1fff (assuming the high bits can't
> be set) so they must be 'special' in some way, but doesn't stop the
> same 'special' values being generated when rescaled.
> 

No, it isn't, as reported by Sashiko. So the patch does not improve
anything while at the same time ignoring the real problems in the
driver.

Guenter