Re: [PATCH v6 6/7] hwmon: Add Nuvoton NCT6694 HWMON support

[Ming Yu]

Dear Vincent and Guenter,

Thank you for reviewing,
I will change the temp_hyst to a signed variable in the next patch.


Thanks,
Ming

Guenter Roeck <linux@xxxxxxxxxxxx> 於 2025年1月26日 週日 下午9:18寫道：
>
> On 1/25/25 23:42, Vincent Mailhol wrote:
> > On 23/01/2025 at 18:11, Ming Yu wrote:
> >> This driver supports Hardware monitor functionality for NCT6694 MFD
> >> device based on USB interface.
> >>
> >> Signed-off-by: Ming Yu <a0282524688@xxxxxxxxx>
> >> ---
> >
> > (...)
> >
> >> +static int nct6694_temp_write(struct device *dev, u32 attr, int channel,
> >> +                          long val)
> >> +{
> >> +    struct nct6694_hwmon_data *data = dev_get_drvdata(dev);
> >> +    struct nct6694_cmd_header cmd_hd;
> >> +    unsigned char temp_hyst;
> >> +    signed char temp_max;
> >> +    int ret;
> >> +
> >> +    guard(mutex)(&data->lock);
> >> +
> >> +    switch (attr) {
> >> +    case hwmon_temp_enable:
> >> +            if (val == 0)
> >> +                    data->hwmon_en.tin_en[channel / 8] &= ~BIT(channel % 8);
> >> +            else if (val == 1)
> >> +                    data->hwmon_en.tin_en[channel / 8] |= BIT(channel % 8);
> >> +            else
> >> +                    return -EINVAL;
> >> +
> >> +            cmd_hd = (struct nct6694_cmd_header) {
> >> +                    .mod = NCT6694_HWMON_MOD,
> >> +                    .cmd = NCT6694_HWMON_CONTROL,
> >> +                    .sel = NCT6694_HWMON_CONTROL_SEL,
> >> +                    .len = cpu_to_le16(sizeof(data->hwmon_en))
> >> +            };
> >> +
> >> +            return nct6694_write_msg(data->nct6694, &cmd_hd,
> >> +                                     &data->hwmon_en);
> >> +    case hwmon_temp_max:
> >> +            cmd_hd = (struct nct6694_cmd_header) {
> >> +                    .mod = NCT6694_HWMON_MOD,
> >> +                    .cmd = NCT6694_HWMON_ALARM,
> >> +                    .sel = NCT6694_HWMON_ALARM_SEL,
> >> +                    .len = cpu_to_le16(sizeof(data->msg->hwmon_alarm))
> >> +            };
> >> +            ret = nct6694_read_msg(data->nct6694, &cmd_hd,
> >> +                                   &data->msg->hwmon_alarm);
> >> +            if (ret)
> >> +                    return ret;
> >> +
> >> +            val = clamp_val(val, -127000, 127000);
> >> +            data->msg->hwmon_alarm.tin_cfg[channel].hl = temp_to_reg(val);
> >> +
> >> +            return nct6694_write_msg(data->nct6694, &cmd_hd,
> >> +                                     &data->msg->hwmon_alarm);
> >> +    case hwmon_temp_max_hyst:
> >> +            cmd_hd = (struct nct6694_cmd_header) {
> >> +                    .mod = NCT6694_HWMON_MOD,
> >> +                    .cmd = NCT6694_HWMON_ALARM,
> >> +                    .sel = NCT6694_HWMON_ALARM_SEL,
> >> +                    .len = cpu_to_le16(sizeof(data->msg->hwmon_alarm))
> >> +            };
> >> +            ret = nct6694_read_msg(data->nct6694, &cmd_hd,
> >> +                                   &data->msg->hwmon_alarm);
> >> +
> >> +            val = clamp_val(val, -127000, 127000);
> >> +            temp_max = data->msg->hwmon_alarm.tin_cfg[channel].hl;
> >> +            temp_hyst = temp_max - temp_to_reg(val);
> >> +            temp_hyst = clamp_val(temp_hyst, 0, 7);
> >
> > temp_hyst is unsigned. It can not be smaller than zero. No need for
> > clamp(), using min here is sufficient.
> >
>
> Wrong conclusion. It needs to be declared as signed variable because
> "temp_max - temp_to_reg(val)" could be negative.
>
> Guenter
>