Re: [PATCH] hwmon: (cros_ec): Hide unconfigured temperature thresholds

[Thomas Weißschuh]

On 2026-07-29 00:38:16+0800, Daniel Schaefer via B4 Relay wrote:
> From: Daniel Schaefer <dhs@xxxxxxxxxx>

Welcome to upstream!

> The EC reports a threshold of 0 K for host thresholds that are not
> configured. Most Framework Computer systems don't use all thresholds.
> E.g. temp_host_warn is left unset and stays at its -273 C / 0 K
> default), see the EC code in zephyr/shim/src/thermal.c:
> 
>   DT_PROP_OR(node_id, temp_host_warn,  -273)
> 
> Previously these unconfigured thresholds were exposed as sysfs limits
> that read back as -273.15 C, which userspace (e.g. s-tui) interpreted as
> a real, permanently-exceeded limit.

In current hwmon-next this should read back as -273C. See commit
9f14280c5ef3 ("hwmon: (cros_ec) Implement custom kelvin to celsius conversions")

> To avoid this we can hide the sysfs attribute for that threshold.

"Avoid this by hiding ..."

> See truncated example below.
> 
> Before:
> 
> > sensors cros_ec-isa-000c
> cpu_f75303@4d:       +36.9°C  (crit = +74.8°C, emerg = +84.8°C)
> 
> After:
> 
> > sensors cros_ec-isa-000c
> cpu_f75303@4d:       +36.9°C  (high = -273.1°C, crit = +74.8°C)
>                               (emerg = +84.8°C)

"Before:" and "After:" are swapped?

> Cc: Tzung-Bi Shih <tzungbi@xxxxxxxxxx>
> Cc: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> Cc: linux@xxxxxxxxxx
> Signed-off-by: Daniel Schaefer <dhs@xxxxxxxxxx>
> ---
>  drivers/hwmon/cros_ec_hwmon.c | 14 ++++++++++++--
>  1 file changed, 12 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
> index 03bfcc40bb7c..57158443dafe 100644
> --- a/drivers/hwmon/cros_ec_hwmon.c
> +++ b/drivers/hwmon/cros_ec_hwmon.c
> @@ -319,6 +319,7 @@ static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_type
>  					u32 attr, int channel)
>  {
>  	const struct cros_ec_hwmon_priv *priv = data;
> +	u32 threshold;
>  	u16 speed;
>  
>  	if (type == hwmon_fan) {
> @@ -334,8 +335,17 @@ static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_type
>  	} else if (type == hwmon_temp) {
>  		if (priv->temp_sensor_names[channel]) {
>  			if (cros_ec_hwmon_attr_is_temp_threshold(attr)) {
> -				if (priv->temp_threshold_supported)
> -					return 0444;
> +				if (!priv->temp_threshold_supported)
> +					return 0;
> +
> +				if (cros_ec_hwmon_read_temp_threshold(priv->cros_ec, channel,
> +								      cros_ec_hwmon_attr_to_thres(attr),
> +								      &threshold) != 0)

Probing would be a bit faster by not calling this for each threshold,
but only doing it once. cros_ec_hwmon_priv::temp_threshold_supported
could become a bitmask for supported thresholds to be read in is_visible().
This can also replace is_cros_ec_cmd_available(EC_CMD_THERMAL_GET_THRESHOLD).

> +					return 0;
> +				if (threshold == 0)
> +					return 0;
> +
> +				return 0444;
>  			} else {
>  				return 0444;
>  			}