Re: [RFC PATCH] hwmon: (nct6775) Ignore 0xffff TSI temperature readings

[Guenter Roeck]

On 8/24/26 11:44, 蔡 德彝 wrote:
> On an NCT6793D, unused TSI temperature channels can return 0xffff.
>
> The driver currently treats every non-zero TSI register value as an
> active channel. This causes unused TSI channels to be exposed through
> hwmon and results in bogus temperature readings of 3892313987
> millidegrees Celsius.
>
> Treat 0xffff as an inactive TSI channel.
>
> With this change, the unused TSI channels are no longer exposed, while
> TSI0 continues to report normally.

As pointed out by Sashiko, the fix is incomplete. The tsi_temp array should
be declared as u16. Also, at runtime, show_tsi_temp() should check if
data->tsi_temp[sattr->index] == 0xffff and return -ENODATA if that is the case.

Thanks,
Guenter

> Tested on an ASRock A320M-HDV R4.0 with an NCT6793D.
>
> Fixes: b68437ace4b8 ("hwmon: (nct6775) add support for TSI temperature registers")
> Assisted-by: ChatGPT:GPT-5.6-Sol
> Signed-off-by: Spector Tsai <Spector.Tsai@xxxxxxxxxxx>
> ---
>   drivers/hwmon/nct6775-core.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/nct6775-core.c b/drivers/hwmon/nct6775-core.c
> index 759ea3d1286e..34e6a01aa4e4 100644
> --- a/drivers/hwmon/nct6775-core.c
> +++ b/drivers/hwmon/nct6775-core.c
> @@ -4339,7 +4339,7 @@ int nct6775_probe(struct device *dev, struct nct6775_data *data,
>   		err = nct6775_read_value(data, data->REG_TSI_TEMP[i], &tmp);
>   		if (err)
>   			return err;
> -		if (tmp)
> +		if (tmp && tmp != 0xffff)
>   			data->have_tsi_temp |= BIT(i);
>   	}
>