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

[Guenter Roeck]

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