Re: [PATCH v2 01/11] hwmon: (amc6821) Stop accepting invalid pwm values

[Guenter Roeck]

On 7/3/24 07:29, Quentin Schulz wrote:
> Hi Guenter,
>
> On 7/1/24 11:23 PM, Guenter Roeck wrote:
> > The pwm value range is well defined from 0..255. Don't accept
> > any values outside this range.
> >
> > Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> > ---
> > v2: Use kstrtou8() instead of kstrtol() where possible.
> >      Limit range of pwm1_auto_point_pwm to 0..254 in patch 1
> >      instead of limiting it later, and do not accept invalid
> >      values for the attribute.
> >
> >   drivers/hwmon/amc6821.c | 15 +++++++++------
> >   1 file changed, 9 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/hwmon/amc6821.c b/drivers/hwmon/amc6821.c
> > index 9b02b304c2f5..eb2d5592a41a 100644
> > --- a/drivers/hwmon/amc6821.c
> > +++ b/drivers/hwmon/amc6821.c
> > @@ -355,13 +355,13 @@ static ssize_t pwm1_store(struct device *dev,
> >   {
> >       struct amc6821_data *data = dev_get_drvdata(dev);
> >       struct i2c_client *client = data->client;
> > -    long val;
> > -    int ret = kstrtol(buf, 10, &val);
> > +    u8 val;
> > +    int ret = kstrtou8(buf, 10, &val);
> >       if (ret)
> >           return ret;
> >       mutex_lock(&data->update_lock);
> > -    data->pwm1 = clamp_val(val , 0, 255);
> > +    data->pwm1 = val;
> >       i2c_smbus_write_byte_data(client, AMC6821_REG_DCY, data->pwm1);
> >       mutex_unlock(&data->update_lock);
> >       return count;
> > @@ -558,13 +558,16 @@ static ssize_t pwm1_auto_point_pwm_store(struct device *dev,
> >       struct amc6821_data *data = dev_get_drvdata(dev);
> >       struct i2c_client *client = data->client;
> >       int dpwm;
> > -    long val;
> > -    int ret = kstrtol(buf, 10, &val);
> > +    u8 val;
> > +    int ret = kstrtou8(buf, 10, &val);
> >       if (ret)
> >           return ret;
> >
> > +    if (val > 254)
>
> Would have appreciated a comment as to why it's 254. My understanding is that the subsystem requires no overlap between multiple pwm_auto_points? 0 being 0 and 2 being 255, we need 1 to be 255?

No idea, really, I just took it from the original code. I don't find a hint
in the code suggesting why 255 would be worse than 0.

> Actually, that doesn't explain why we allow 0 here, so maybe I'm just clueless :)
Yes, agreed, that doesn't really make sense. I'll change the upper limit to 255.

> The change itself though:
> Reviewed-by: Quentin Schulz <quentin.schulz@xxxxxxxxx>
... but I'll also keep that tag unless you start screaming.

Thanks,
Guenter