[PATCH v2 1/2] dt-bindings: hwmon: chipcap2: Add label property

[PATCH v2 1/2] dt-bindings: hwmon: chipcap2: Add label property

[Flaviu Nistor]

Add support for an optional label property similar to other hwmon devices.
This allows, in case of boards with multiple CHIPCAP2 sensors, to assign
distinct names to each instance.

Signed-off-by: Flaviu Nistor <flaviu.nistor@gmail.com>
---
Changes in v2:
- Implement suggestion from Javier Carrasco as proposed by Krzysztof Kozlowski.
- Link to v1: https://lore.kernel.org/all/20260622122200.14245-1-flaviu.nistor@gmail.com/

 .../devicetree/bindings/hwmon/amphenol,chipcap2.yaml        | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml b/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
index 17351fdbefce..56b0cecfca5f 100644
--- a/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
+++ b/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
@@ -45,6 +45,8 @@ properties:
       - const: low
       - const: high
 
+  label: true
+
   vdd-supply:
     description:
       Dedicated, controllable supply-regulator to reset the device and
@@ -55,6 +57,9 @@ required:
   - reg
   - vdd-supply
 
+allOf:
+  - $ref: hwmon-common.yaml#
+
 additionalProperties: false
 
 examples:
@@ -72,6 +77,7 @@ examples:
                          <5 IRQ_TYPE_EDGE_RISING>,
                          <6 IRQ_TYPE_EDGE_RISING>;
             interrupt-names = "ready", "low", "high";
+            label = "Room";
             vdd-supply = <&reg_vdd>;
         };
     };
-- 
2.34.1

[PATCH v2 2/2] hwmon: (chipcap2) Add support for label

[Flaviu Nistor]

Add support for label sysfs attribute similar to other hwmon devices.
This is particularly useful for systems with multiple sensors on the
same board, where identifying individual sensors is much easier since
labels can be defined via device tree.

Signed-off-by: Flaviu Nistor <flaviu.nistor@gmail.com>
---
Changes in v2:
- No change for this patch in the patch series. 
- Link to v1: https://lore.kernel.org/all/20260622122200.14245-1-flaviu.nistor@gmail.com/

 Documentation/hwmon/chipcap2.rst |  2 ++
 drivers/hwmon/chipcap2.c         | 25 +++++++++++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/Documentation/hwmon/chipcap2.rst b/Documentation/hwmon/chipcap2.rst
index dc165becc64c..c38d87b91b69 100644
--- a/Documentation/hwmon/chipcap2.rst
+++ b/Documentation/hwmon/chipcap2.rst
@@ -70,4 +70,6 @@ humidity1_min_hyst:             RW      humidity low hystersis
 humidity1_max_hyst:             RW      humidity high hystersis
 humidity1_min_alarm:            RO      humidity low alarm indicator
 humidity1_max_alarm:            RO      humidity high alarm indicator
+humidity1_label:                RO      descriptive name for the sensor
+temp1_label:                    RO      descriptive name for the sensor
 =============================== ======= ========================================
diff --git a/drivers/hwmon/chipcap2.c b/drivers/hwmon/chipcap2.c
index 4aecf463180f..086571d556b7 100644
--- a/drivers/hwmon/chipcap2.c
+++ b/drivers/hwmon/chipcap2.c
@@ -22,6 +22,8 @@
 #include <linux/irq.h>
 #include <linux/module.h>
 #include <linux/regulator/consumer.h>
+#include <linux/mod_devicetable.h>
+#include <linux/property.h>
 
 #define CC2_START_CM			0xA0
 #define CC2_START_NOM			0x80
@@ -83,6 +85,7 @@ struct cc2_data {
 	struct i2c_client *client;
 	struct regulator *regulator;
 	const char *name;
+	const char *label;
 	int irq_ready;
 	int irq_low;
 	int irq_high;
@@ -449,6 +452,8 @@ static umode_t cc2_is_visible(const void *data, enum hwmon_sensor_types type,
 		switch (attr) {
 		case hwmon_humidity_input:
 			return 0444;
+		case hwmon_humidity_label:
+			return cc2->label ? 0444 : 0;
 		case hwmon_humidity_min_alarm:
 			return cc2->rh_alarm.low_alarm_visible ? 0444 : 0;
 		case hwmon_humidity_max_alarm:
@@ -466,6 +471,8 @@ static umode_t cc2_is_visible(const void *data, enum hwmon_sensor_types type,
 		switch (attr) {
 		case hwmon_temp_input:
 			return 0444;
+		case hwmon_temp_label:
+			return cc2->label ? 0444 : 0;
 		default:
 			return 0;
 		}
@@ -552,6 +559,16 @@ static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val)
 	return 0;
 }
 
+static int cc2_read_string(struct device *dev, enum hwmon_sensor_types type,
+			   u32 attr, int channel, const char **str)
+{
+	struct cc2_data *data = dev_get_drvdata(dev);
+
+	*str = data->label;
+
+	return 0;
+}
+
 static int cc2_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
 		    int channel, long *val)
 {
@@ -670,8 +687,9 @@ static int cc2_request_alarm_irqs(struct cc2_data *data, struct device *dev)
 }
 
 static const struct hwmon_channel_info *cc2_info[] = {
-	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
-	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT | HWMON_H_MIN | HWMON_H_MAX |
+	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_LABEL),
+	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT | HWMON_H_LABEL |
+			   HWMON_H_MIN | HWMON_H_MAX |
 			   HWMON_H_MIN_HYST | HWMON_H_MAX_HYST |
 			   HWMON_H_MIN_ALARM | HWMON_H_MAX_ALARM),
 	NULL
@@ -680,6 +698,7 @@ static const struct hwmon_channel_info *cc2_info[] = {
 static const struct hwmon_ops cc2_hwmon_ops = {
 	.is_visible = cc2_is_visible,
 	.read = cc2_read,
+	.read_string = cc2_read_string,
 	.write = cc2_write,
 };
 
@@ -710,6 +729,8 @@ static int cc2_probe(struct i2c_client *client)
 		return dev_err_probe(dev, PTR_ERR(data->regulator),
 				     "Failed to get regulator\n");
 
+	device_property_read_string(dev, "label", &data->label);
+
 	ret = cc2_request_ready_irq(data, dev);
 	if (ret)
 		return dev_err_probe(dev, ret, "Failed to request ready irq\n");
-- 
2.34.1

Re: [PATCH v2 2/2] hwmon: (chipcap2) Add support for label

[sashiko-bot]

> Add support for label sysfs attribute similar to other hwmon devices.
> This is particularly useful for systems with multiple sensors on the
> same board, where identifying individual sensors is much easier since
> labels can be defined via device tree.
> 
> Signed-off-by: Flaviu Nistor <flaviu.nistor@gmail.com>

Sashiko has reviewed this patch and found no issues. It looks great!

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260625160423.17882-1-flaviu.nistor@gmail.com?part=2

Re: [PATCH v2 2/2] hwmon: (chipcap2) Add support for label

[Javier Carrasco]

On Thu Jun 25, 2026 at 6:04 PM CEST, Flaviu Nistor wrote:
> Add support for label sysfs attribute similar to other hwmon devices.
> This is particularly useful for systems with multiple sensors on the
> same board, where identifying individual sensors is much easier since
> labels can be defined via device tree.
>
> Signed-off-by: Flaviu Nistor <flaviu.nistor@gmail.com>
> ---
> Changes in v2:
> - No change for this patch in the patch series.
> - Link to v1: https://lore.kernel.org/all/20260622122200.14245-1-flaviu.nistor@gmail.com/
>
>  Documentation/hwmon/chipcap2.rst |  2 ++
>  drivers/hwmon/chipcap2.c         | 25 +++++++++++++++++++++++--
>  2 files changed, 25 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/hwmon/chipcap2.rst b/Documentation/hwmon/chipcap2.rst
> index dc165becc64c..c38d87b91b69 100644
> --- a/Documentation/hwmon/chipcap2.rst
> +++ b/Documentation/hwmon/chipcap2.rst
> @@ -70,4 +70,6 @@ humidity1_min_hyst:             RW      humidity low hystersis
>  humidity1_max_hyst:             RW      humidity high hystersis
>  humidity1_min_alarm:            RO      humidity low alarm indicator
>  humidity1_max_alarm:            RO      humidity high alarm indicator
> +humidity1_label:                RO      descriptive name for the sensor
> +temp1_label:                    RO      descriptive name for the sensor
>  =============================== ======= ========================================
> diff --git a/drivers/hwmon/chipcap2.c b/drivers/hwmon/chipcap2.c
> index 4aecf463180f..086571d556b7 100644
> --- a/drivers/hwmon/chipcap2.c
> +++ b/drivers/hwmon/chipcap2.c
> @@ -22,6 +22,8 @@
>  #include <linux/irq.h>
>  #include <linux/module.h>
>  #include <linux/regulator/consumer.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/property.h>
>
>  #define CC2_START_CM			0xA0
>  #define CC2_START_NOM			0x80
> @@ -83,6 +85,7 @@ struct cc2_data {
>  	struct i2c_client *client;
>  	struct regulator *regulator;
>  	const char *name;
> +	const char *label;
>  	int irq_ready;
>  	int irq_low;
>  	int irq_high;
> @@ -449,6 +452,8 @@ static umode_t cc2_is_visible(const void *data, enum hwmon_sensor_types type,
>  		switch (attr) {
>  		case hwmon_humidity_input:
>  			return 0444;
> +		case hwmon_humidity_label:
> +			return cc2->label ? 0444 : 0;
>  		case hwmon_humidity_min_alarm:
>  			return cc2->rh_alarm.low_alarm_visible ? 0444 : 0;
>  		case hwmon_humidity_max_alarm:
> @@ -466,6 +471,8 @@ static umode_t cc2_is_visible(const void *data, enum hwmon_sensor_types type,
>  		switch (attr) {
>  		case hwmon_temp_input:
>  			return 0444;
> +		case hwmon_temp_label:
> +			return cc2->label ? 0444 : 0;
>  		default:
>  			return 0;
>  		}
> @@ -552,6 +559,16 @@ static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val)
>  	return 0;
>  }
>
> +static int cc2_read_string(struct device *dev, enum hwmon_sensor_types type,
> +			   u32 attr, int channel, const char **str)
> +{
> +	struct cc2_data *data = dev_get_drvdata(dev);
> +
> +	*str = data->label;
> +
> +	return 0;
> +}
> +
>  static int cc2_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
>  		    int channel, long *val)
>  {
> @@ -670,8 +687,9 @@ static int cc2_request_alarm_irqs(struct cc2_data *data, struct device *dev)
>  }
>
>  static const struct hwmon_channel_info *cc2_info[] = {
> -	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
> -	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT | HWMON_H_MIN | HWMON_H_MAX |
> +	HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_LABEL),
> +	HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT | HWMON_H_LABEL |
> +			   HWMON_H_MIN | HWMON_H_MAX |
>  			   HWMON_H_MIN_HYST | HWMON_H_MAX_HYST |
>  			   HWMON_H_MIN_ALARM | HWMON_H_MAX_ALARM),
>  	NULL
> @@ -680,6 +698,7 @@ static const struct hwmon_channel_info *cc2_info[] = {
>  static const struct hwmon_ops cc2_hwmon_ops = {
>  	.is_visible = cc2_is_visible,
>  	.read = cc2_read,
> +	.read_string = cc2_read_string,
>  	.write = cc2_write,
>  };
>
> @@ -710,6 +729,8 @@ static int cc2_probe(struct i2c_client *client)
>  		return dev_err_probe(dev, PTR_ERR(data->regulator),
>  				     "Failed to get regulator\n");
>
> +	device_property_read_string(dev, "label", &data->label);
> +
>  	ret = cc2_request_ready_irq(data, dev);
>  	if (ret)
>  		return dev_err_probe(dev, ret, "Failed to request ready irq\n");

Reviewed-by: Javier Carrasco <javier.carrasco.cruz@gmail.com>

Re: [PATCH v2 1/2] dt-bindings: hwmon: chipcap2: Add label property

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The threaded interrupt handlers modify alarm state flags without locking, creating a race condition with sysfs reads that can result in lost alarm events.
--

commit 7c977021bab8a6a8bb249ac3b4ad711dbe88c4ff
Author: Flaviu Nistor <flaviu.nistor@gmail.com>

dt-bindings: hwmon: chipcap2: Add label property

This commit adds support for an optional label property similar to other
hwmon devices. This allows assigning distinct names to each CHIPCAP2
sensor instance on boards with multiple sensors.

> diff --git a/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml b/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
> index 17351fdbefce6..56b0cecfca5fb 100644
> --- a/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
> +++ b/Documentation/devicetree/bindings/hwmon/amphenol,chipcap2.yaml
> @@ -45,6 +45,8 @@ properties:
>        - const: low
>        - const: high
>  
> +  label: true
> +
>    vdd-supply:

[ ... ]

While reviewing the hwmon driver code for this hardware, I noticed a
potential locking issue in the interrupt handling.

> --- a/drivers/hwmon/chipcap2.c
> +++ b/drivers/hwmon/chipcap2.c
[ ... ]
> static irqreturn_t cc2_low_interrupt(int irq, void *data)
> {
> 	struct cc2_data *cc2 = data;
> 
> 	if (cc2->process_irqs) {
> 		hwmon_notify_event(cc2->hwmon, hwmon_humidity,
> 				   hwmon_humidity_min_alarm, CC2_CHAN_HUMIDITY);
> 		cc2->rh_alarm.low_alarm = true;
                ^^^^

[Severity: High]
This isn't a bug introduced by this patch, but the threaded interrupt
handler modifies the min alarm flag without acquiring a lock. Could this
create a race condition where an active alarm gets overwritten?

> 	}
> 
> 	return IRQ_HANDLED;
> }
> 
> static irqreturn_t cc2_high_interrupt(int irq, void *data)
> {
> 	struct cc2_data *cc2 = data;
> 
> 	if (cc2->process_irqs) {
> 		hwmon_notify_event(cc2->hwmon, hwmon_humidity,
> 				   hwmon_humidity_max_alarm, CC2_CHAN_HUMIDITY);
> 		cc2->rh_alarm.high_alarm = true;
                ^^^^

[Severity: High]
This is a pre-existing issue, but the max alarm flag is also modified
here without locking.

> 	}
> 
> 	return IRQ_HANDLED;
> }
> 
> static int cc2_humidity_min_alarm_status(struct cc2_data *data, long *val)
> {
> 	long measurement, min_hyst;
> 	int ret;
> 
> 	ret = cc2_read_hyst_and_measure(data, CC2_R_ALARM_L_OFF, &min_hyst,
> 					&measurement);
> 	if (ret < 0)
> 		return ret;
> 
> 	if (data->rh_alarm.low_alarm) {
> 		*val = (measurement < min_hyst) ? 1 : 0;
> 		data->rh_alarm.low_alarm = *val;
                ^^^^

[Severity: High]
This isn't a bug introduced by this patch, but the sysfs read thread
performs an unprotected read-modify-write on the alarm state flag here.

If a sysfs read of the alarm status evaluates the current measurement
over the I2C bus, and cc2_low_interrupt() concurrently receives an
alarm setting low_alarm to true, could the sysfs thread subsequently
overwrite the active alarm flag with 0 based on stale measurement data?

The hwmon subsystem documentation mentions that hwmon_lock() or custom
locking should be used to serialize sysfs operations with interrupt
handling.

> 	} else {
> 		*val = 0;
> 	}
> 
> 	return 0;
> }
> 
> static int cc2_humidity_max_alarm_status(struct cc2_data *data, long *val)
> {
> 	long measurement, max_hyst;
> 	int ret;
> 
> 	ret = cc2_read_hyst_and_measure(data, CC2_R_ALARM_H_OFF, &max_hyst,
> 					&measurement);
> 	if (ret < 0)
> 		return ret;
> 
> 	if (data->rh_alarm.high_alarm) {
> 		*val = (measurement > max_hyst) ? 1 : 0;
> 		data->rh_alarm.high_alarm = *val;
                ^^^^

[Severity: High]
This is a pre-existing issue, but the max alarm sysfs read also writes
back the max alarm flag without locking. Does this present the same risk
of lost alarm events if cc2_high_interrupt() runs concurrently?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260625160423.17882-1-flaviu.nistor@gmail.com?part=1

Re: [PATCH v2 1/2] dt-bindings: hwmon: chipcap2: Add label property

[Krzysztof Kozlowski]

On Thu, Jun 25, 2026 at 07:04:22PM +0300, Flaviu Nistor wrote:
> Add support for an optional label property similar to other hwmon devices.
> This allows, in case of boards with multiple CHIPCAP2 sensors, to assign
> distinct names to each instance.
> 
> Signed-off-by: Flaviu Nistor <flaviu.nistor@gmail.com>
> ---
> Changes in v2:
> - Implement suggestion from Javier Carrasco as proposed by Krzysztof Kozlowski.
> - Link to v1: https://lore.kernel.org/all/20260622122200.14245-1-flaviu.nistor@gmail.com/
> 
>  .../devicetree/bindings/hwmon/amphenol,chipcap2.yaml        | 6 ++++++
>  1 file changed, 6 insertions(+)

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>

Best regards,
Krzysztof