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

[Daniel Schaefer via B4 Relay <devnull+dhs.frame.work@kernel.org>]

From: Daniel Schaefer <dhs@frame.work>

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.

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

Cc: Tzung-Bi Shih <tzungbi@kernel.org>
Cc: Thomas Weißschuh <linux@weissschuh.net>
Cc: linux@frame.work
Signed-off-by: Daniel Schaefer <dhs@frame.work>
---
 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)
+					return 0;
+				if (threshold == 0)
+					return 0;
+
+				return 0444;
 			} else {
 				return 0444;
 			}

---
base-commit: 58717b2a1365d06c8c64b72aa948541b53fe31eb
change-id: 20260729-crosec-hwmon-warn-default-9f3ca86ed809

Best regards,
-- 
Daniel Schaefer <dhs@frame.work>