The ChromeOS Embedded Controller exposes fan speed and temperature
readings.
Expose this data through the hwmon subsystem.

The driver is designed to be probed via the cros_ec mfd device.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 Documentation/hwmon/cros_ec_hwmon.rst |  26 +++
 Documentation/hwmon/index.rst         |   1 +
 MAINTAINERS                           |   8 +
 drivers/hwmon/Kconfig                 |  11 ++
 drivers/hwmon/Makefile                |   1 +
 drivers/hwmon/cros_ec_hwmon.c         | 291 ++++++++++++++++++++++++++++++++++
 6 files changed, 338 insertions(+)

diff --git a/Documentation/hwmon/cros_ec_hwmon.rst b/Documentation/hwmon/cros_ec_hwmon.rst
new file mode 100644
index 000000000000..47ecae983bdb
--- /dev/null
+++ b/Documentation/hwmon/cros_ec_hwmon.rst
@@ -0,0 +1,26 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver cros_ec_hwmon
+===========================
+
+Supported chips:
+
+  * ChromeOS embedded controllers.
+
+    Prefix: 'cros_ec'
+
+    Addresses scanned: -
+
+Author:
+
+  - Thomas Weißschuh <linux@weissschuh.net>
+
+Description
+-----------
+
+This driver implements support for hardware monitoring commands exposed by the
+ChromeOS embedded controller used in Chromebooks and other devices.
+
+The channel labels exposed via hwmon are retrieved from the EC itself.
+
+Fan and temperature readings are supported.
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 03d313af469a..342ea5deba24 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -58,6 +58,7 @@ Hardware Monitoring Kernel Drivers
    coretemp
    corsair-cpro
    corsair-psu
+   cros_ec_hwmon
    da9052
    da9055
    dell-smm-hwmon
diff --git a/MAINTAINERS b/MAINTAINERS
index d6c90161c7bf..0c85aa5073e7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -5135,6 +5135,14 @@ S:	Maintained
 F:	Documentation/devicetree/bindings/sound/google,cros-ec-codec.yaml
 F:	sound/soc/codecs/cros_ec_codec.*
 
+CHROMEOS EC HARDWARE MONITORING
+M:	Thomas Weißschuh <thomas@weissschuh.net>
+L:	chrome-platform@lists.linux.dev
+L:	linux-hwmon@vger.kernel.org
+S:	Maintained
+F:	Documentation/hwmon/chros_ec_hwmon.rst
+F:	drivers/hwmon/cros_ec_hwmon.c
+
 CHROMEOS EC SUBDRIVERS
 M:	Benson Leung <bleung@chromium.org>
 R:	Guenter Roeck <groeck@chromium.org>
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index e14ae18a973b..702dc45ea405 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -506,6 +506,17 @@ config SENSORS_CORSAIR_PSU
 	  This driver can also be built as a module. If so, the module
 	  will be called corsair-psu.
 
+config SENSORS_CROS_EC
+	tristate "ChromeOS Embedded Controller sensors"
+	depends on MFD_CROS_EC_DEV
+	default MFD_CROS_EC_DEV
+	help
+	  If you say yes here you get support for ChromeOS Embedded Controller
+	  sensors.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called cros_ec_hwmon.
+
 config SENSORS_DRIVETEMP
 	tristate "Hard disk drives with temperature sensors"
 	depends on SCSI && ATA
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index e3f25475d1f0..4fb14dd1eafd 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -64,6 +64,7 @@ obj-$(CONFIG_SENSORS_CHIPCAP2) += chipcap2.o
 obj-$(CONFIG_SENSORS_CORETEMP)	+= coretemp.o
 obj-$(CONFIG_SENSORS_CORSAIR_CPRO) += corsair-cpro.o
 obj-$(CONFIG_SENSORS_CORSAIR_PSU) += corsair-psu.o
+obj-$(CONFIG_SENSORS_CROS_EC)	+= cros_ec_hwmon.o
 obj-$(CONFIG_SENSORS_DA9052_ADC)+= da9052-hwmon.o
 obj-$(CONFIG_SENSORS_DA9055)+= da9055-hwmon.o
 obj-$(CONFIG_SENSORS_DELL_SMM)	+= dell-smm-hwmon.o
diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
new file mode 100644
index 000000000000..2d9c1f4ec09a
--- /dev/null
+++ b/drivers/hwmon/cros_ec_hwmon.c
@@ -0,0 +1,291 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  ChromesOS EC driver for hwmon
+ *
+ *  Copyright (C) 2024 Thomas Weißschuh <linux@weissschuh.net>
+ */
+
+#include <linux/device.h>
+#include <linux/hwmon.h>
+#include <linux/mod_devicetable.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/platform_data/cros_ec_commands.h>
+#include <linux/platform_data/cros_ec_proto.h>
+#include <linux/types.h>
+#include <linux/units.h>
+
+#define DRV_NAME	"cros-ec-hwmon"
+
+struct cros_ec_hwmon_priv {
+	struct cros_ec_device *cros_ec;
+	const char *temp_sensor_names[EC_TEMP_SENSOR_ENTRIES + EC_TEMP_SENSOR_B_ENTRIES];
+	u8 usable_fans;
+};
+
+static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index, u16 *speed)
+{
+	u16 data;
+	int ret;
+
+	ret = cros_ec_cmd_readmem(cros_ec, EC_MEMMAP_FAN + index * 2, 2, &data);
+	if (ret < 0)
+		return ret;
+
+	data = le16_to_cpu(data);
+	*speed = data;
+
+	if (data == EC_FAN_SPEED_NOT_PRESENT || data == EC_FAN_SPEED_STALLED)
+		return -EIO;
+	return 0;
+}
+
+static int cros_ec_hwmon_read_temp(struct cros_ec_device *cros_ec, u8 index, u8 *data)
+{
+	unsigned int offset;
+	int ret;
+
+	if (index < EC_TEMP_SENSOR_ENTRIES)
+		offset = EC_MEMMAP_TEMP_SENSOR + index;
+	else
+		offset = EC_MEMMAP_TEMP_SENSOR_B + index - EC_TEMP_SENSOR_ENTRIES;
+
+	ret = cros_ec_cmd_readmem(cros_ec, offset, 1, data);
+	if (ret < 0)
+		return ret;
+
+	if (*data == EC_TEMP_SENSOR_NOT_PRESENT ||
+	    *data == EC_TEMP_SENSOR_ERROR ||
+	    *data == EC_TEMP_SENSOR_NOT_POWERED ||
+	    *data == EC_TEMP_SENSOR_NOT_CALIBRATED)
+		return -EIO;
+
+	return 0;
+}
+
+static int cros_ec_hwmon_read_temp_sensor_info(struct cros_ec_device *cros_ec, u8 id,
+					       struct ec_response_temp_sensor_get_info *resp)
+{
+	int ret;
+	struct {
+		struct cros_ec_command msg;
+		union {
+			struct ec_params_temp_sensor_get_info req;
+			struct ec_response_temp_sensor_get_info resp;
+		} __packed data;
+	} __packed buf = {
+		.msg = {
+			.version = 0,
+			.command = EC_CMD_TEMP_SENSOR_GET_INFO,
+			.insize  = sizeof(buf.data.resp),
+			.outsize = sizeof(buf.data.req),
+		},
+		.data.req.id = id,
+	};
+
+	ret = cros_ec_cmd_xfer_status(cros_ec, &buf.msg);
+	if (ret < 0)
+		return ret;
+
+	*resp = buf.data.resp;
+	return 0;
+}
+
+static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+			      u32 attr, int channel, long *val)
+{
+	struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
+	int ret = -ENODATA;
+	u16 speed = 0;
+	u8 temp = 0;
+
+	if (type == hwmon_fan && attr == hwmon_fan_input) {
+		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
+		if (ret == 0)
+			*val = speed;
+	} else if (type == hwmon_fan && attr == hwmon_fan_fault) {
+		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
+		if (ret == -EIO && speed == EC_FAN_SPEED_STALLED)
+			ret = 0;
+		if (ret == 0)
+			*val = speed == EC_FAN_SPEED_STALLED;
+	} else if (type == hwmon_temp && attr == hwmon_temp_input) {
+		ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
+		if (ret == 0)
+			*val = kelvin_to_millicelsius((((long)temp) + EC_TEMP_SENSOR_OFFSET));
+	} else if (type == hwmon_temp && attr == hwmon_temp_fault) {
+		ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
+		if (ret == -EIO && speed == EC_TEMP_SENSOR_ERROR)
+			ret = 0;
+		if (ret == 0)
+			*val = temp == EC_TEMP_SENSOR_ERROR;
+	}
+
+	return ret;
+}
+
+static int cros_ec_hwmon_read_string(struct device *dev, enum hwmon_sensor_types type,
+				     u32 attr, int channel, const char **str)
+{
+	struct cros_ec_hwmon_priv *priv = dev_get_drvdata(dev);
+
+	if (type == hwmon_temp && attr == hwmon_temp_label) {
+		*str = priv->temp_sensor_names[channel];
+		return 0;
+	}
+
+	return -ENODATA;
+}
+
+static umode_t cros_ec_hwmon_is_visible(const void *data, enum hwmon_sensor_types type,
+					u32 attr, int channel)
+{
+	const struct cros_ec_hwmon_priv *priv = data;
+
+	if (type == hwmon_fan) {
+		if (priv->usable_fans & BIT(channel))
+			return 0444;
+	} else if (type == hwmon_temp) {
+		if (priv->temp_sensor_names[channel])
+			return 0444;
+	}
+
+	return 0;
+}
+
+static const struct hwmon_channel_info * const cros_ec_hwmon_info[] = {
+	HWMON_CHANNEL_INFO(fan,
+			   HWMON_F_INPUT | HWMON_F_FAULT,
+			   HWMON_F_INPUT | HWMON_F_FAULT,
+			   HWMON_F_INPUT | HWMON_F_FAULT,
+			   HWMON_F_INPUT | HWMON_F_FAULT),
+	HWMON_CHANNEL_INFO(temp,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL,
+			   HWMON_T_INPUT | HWMON_T_FAULT | HWMON_T_LABEL),
+	NULL
+};
+
+static const struct hwmon_ops cros_ec_hwmon_ops = {
+	.read = cros_ec_hwmon_read,
+	.read_string = cros_ec_hwmon_read_string,
+	.is_visible = cros_ec_hwmon_is_visible,
+};
+
+static const struct hwmon_chip_info cros_ec_hwmon_chip_info = {
+	.ops = &cros_ec_hwmon_ops,
+	.info = cros_ec_hwmon_info,
+};
+
+static void cros_ec_hwmon_probe_temp_sensors(struct device *dev, struct cros_ec_hwmon_priv *priv,
+					     u8 thermal_version)
+{
+	struct ec_response_temp_sensor_get_info info;
+	size_t candidates, i, sensor_name_size;
+	int ret;
+	u8 temp;
+
+	if (thermal_version < 2)
+		candidates = EC_TEMP_SENSOR_ENTRIES;
+	else
+		candidates = ARRAY_SIZE(priv->temp_sensor_names);
+
+	for (i = 0; i < candidates; i++) {
+		if (cros_ec_hwmon_read_temp(priv->cros_ec, i, &temp) != 0)
+			continue;
+
+		ret = cros_ec_hwmon_read_temp_sensor_info(priv->cros_ec, i, &info);
+		if (ret < 0)
+			continue;
+
+		sensor_name_size = strnlen(info.sensor_name, sizeof(info.sensor_name));
+		priv->temp_sensor_names[i] = devm_kasprintf(dev, GFP_KERNEL, "%*s",
+							    (int)sensor_name_size,
+							    info.sensor_name);
+	}
+}
+
+static void cros_ec_hwmon_probe_fans(struct device *dev, struct cros_ec_hwmon_priv *priv)
+{
+	u16 speed;
+	size_t i;
+	int ret;
+
+	for (i = 0; i < EC_FAN_SPEED_ENTRIES; i++) {
+		speed = EC_FAN_SPEED_NOT_PRESENT;
+		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, i, &speed);
+		if (ret == 0 || speed != EC_FAN_SPEED_NOT_PRESENT)
+			priv->usable_fans |= BIT(i);
+	}
+}
+
+static int cros_ec_hwmon_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct cros_ec_dev *ec_dev = dev_get_drvdata(dev->parent);
+	struct cros_ec_device *cros_ec = ec_dev->ec_dev;
+	struct cros_ec_hwmon_priv *priv;
+	struct device *hwmon_dev;
+	u8 thermal_version;
+	int ret;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	ret = cros_ec_cmd_readmem(cros_ec, EC_MEMMAP_THERMAL_VERSION, 1, &thermal_version);
+	if (ret < 0)
+		return ret;
+
+	/* Covers both fan and temp sensors */
+	if (thermal_version == 0)
+		return -ENODEV;
+
+	priv->cros_ec = cros_ec;
+
+	cros_ec_hwmon_probe_temp_sensors(dev, priv, thermal_version);
+	cros_ec_hwmon_probe_fans(dev, priv);
+
+	hwmon_dev = devm_hwmon_device_register_with_info(dev, "cros_ec", priv,
+							 &cros_ec_hwmon_chip_info, NULL);
+
+	return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct platform_device_id cros_ec_hwmon_id[] = {
+	{ DRV_NAME, 0 },
+	{ }
+};
+
+static struct platform_driver cros_ec_hwmon_driver = {
+	.driver.name	= DRV_NAME,
+	.probe		= cros_ec_hwmon_probe,
+	.id_table	= cros_ec_hwmon_id,
+};
+module_platform_driver(cros_ec_hwmon_driver);
+
+MODULE_DEVICE_TABLE(platform, cros_ec_hwmon_id);
+MODULE_DESCRIPTION("ChromeOS EC Hardware Monitoring Driver");
+MODULE_AUTHOR("Thomas Weißschuh <linux@weissschuh.net");
+MODULE_LICENSE("GPL");

-- 
2.45.1

On Mon, May 27, 2024 at 10:58:32PM +0200, Thomas Weißschuh wrote:
> diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
[...]
> + *  ChromesOS EC driver for hwmon

s/ChromesOS/ChromeOS/.

> +struct cros_ec_hwmon_priv {
> +	struct cros_ec_device *cros_ec;
> +	const char *temp_sensor_names[EC_TEMP_SENSOR_ENTRIES + EC_TEMP_SENSOR_B_ENTRIES];
> +	u8 usable_fans;
> +};
> +
> +static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index, u16 *speed)
> +{
> +	u16 data;
> +	int ret;
> +
> +	ret = cros_ec_cmd_readmem(cros_ec, EC_MEMMAP_FAN + index * 2, 2, &data);
> +	if (ret < 0)
> +		return ret;
> +
> +	data = le16_to_cpu(data);
> +	*speed = data;
> +
> +	if (data == EC_FAN_SPEED_NOT_PRESENT || data == EC_FAN_SPEED_STALLED)
> +		return -EIO;

`data` could be eliminated; use `*speed` instead.

> +static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> +			      u32 attr, int channel, long *val)
> +{
[...]
> +	u16 speed = 0;
> +	u8 temp = 0;

They don't need to initialize.

> +	if (type == hwmon_fan && attr == hwmon_fan_input) {
> +		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
> +		if (ret == 0)
> +			*val = speed;
> +	} else if (type == hwmon_fan && attr == hwmon_fan_fault) {
> +		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
> +		if (ret == -EIO && speed == EC_FAN_SPEED_STALLED)
> +			ret = 0;
> +		if (ret == 0)
> +			*val = speed == EC_FAN_SPEED_STALLED;
> +	} else if (type == hwmon_temp && attr == hwmon_temp_input) {
> +		ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
> +		if (ret == 0)
> +			*val = kelvin_to_millicelsius((((long)temp) + EC_TEMP_SENSOR_OFFSET));
> +	} else if (type == hwmon_temp && attr == hwmon_temp_fault) {
> +		ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
> +		if (ret == -EIO && speed == EC_TEMP_SENSOR_ERROR)
> +			ret = 0;
> +		if (ret == 0)
> +			*val = temp == EC_TEMP_SENSOR_ERROR;
> +	}

Refactoring them by switch .. case .. may improve the readability.

On 2024-05-28 06:39:25+0000, Tzung-Bi Shih wrote:
> On Mon, May 27, 2024 at 10:58:32PM +0200, Thomas Weißschuh wrote:
> > diff --git a/drivers/hwmon/cros_ec_hwmon.c b/drivers/hwmon/cros_ec_hwmon.c
> [...]
> > + *  ChromesOS EC driver for hwmon
> 
> s/ChromesOS/ChromeOS/.

Ack. Copy-and-paste...

> > +struct cros_ec_hwmon_priv {
> > +	struct cros_ec_device *cros_ec;
> > +	const char *temp_sensor_names[EC_TEMP_SENSOR_ENTRIES + EC_TEMP_SENSOR_B_ENTRIES];
> > +	u8 usable_fans;
> > +};
> > +
> > +static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index, u16 *speed)
> > +{
> > +	u16 data;
> > +	int ret;
> > +
> > +	ret = cros_ec_cmd_readmem(cros_ec, EC_MEMMAP_FAN + index * 2, 2, &data);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	data = le16_to_cpu(data);
> > +	*speed = data;
> > +
> > +	if (data == EC_FAN_SPEED_NOT_PRESENT || data == EC_FAN_SPEED_STALLED)
> > +		return -EIO;
> 
> `data` could be eliminated; use `*speed` instead.

Then the le16 value would need to be written directly to the out
parameter. The current usage relies on *speed (sometimes) being set even
if ret != 0.

(See next response block)

> 
> > +static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> > +			      u32 attr, int channel, long *val)
> > +{
> [...]
> > +	u16 speed = 0;
> > +	u8 temp = 0;
> 
> They don't need to initialize.

They need to.

The logic

if (ret == -EIO && speed == EC_FAN_SPEED_STALLED)
	ret = 0;

relies on -EIO and a write to speed from cros_ec_hwmon_read_fan_speed().

But if cros_ec_cmd_readmem() already returns -EIO, then speed would be
uninitialized.

I'll see if I can make this clearer somehow.

> 
> > +	if (type == hwmon_fan && attr == hwmon_fan_input) {
> > +		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
> > +		if (ret == 0)
> > +			*val = speed;
> > +	} else if (type == hwmon_fan && attr == hwmon_fan_fault) {
> > +		ret = cros_ec_hwmon_read_fan_speed(priv->cros_ec, channel, &speed);
> > +		if (ret == -EIO && speed == EC_FAN_SPEED_STALLED)
> > +			ret = 0;
> > +		if (ret == 0)
> > +			*val = speed == EC_FAN_SPEED_STALLED;
> > +	} else if (type == hwmon_temp && attr == hwmon_temp_input) {
> > +		ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
> > +		if (ret == 0)
> > +			*val = kelvin_to_millicelsius((((long)temp) + EC_TEMP_SENSOR_OFFSET));
> > +	} else if (type == hwmon_temp && attr == hwmon_temp_fault) {
> > +		ret = cros_ec_hwmon_read_temp(priv->cros_ec, channel, &temp);
> > +		if (ret == -EIO && speed == EC_TEMP_SENSOR_ERROR)
> > +			ret = 0;
> > +		if (ret == 0)
> > +			*val = temp == EC_TEMP_SENSOR_ERROR;
> > +	}
> 
> Refactoring them by switch .. case .. may improve the readability.

It would introduce another level of indentation, which I tried to avoid.
But some vertical whitespace would be useful indeed.

On Tue, May 28, 2024 at 09:09:28AM +0200, Thomas Weißschuh wrote:
> On 2024-05-28 06:39:25+0000, Tzung-Bi Shih wrote:
> > On Mon, May 27, 2024 at 10:58:32PM +0200, Thomas Weißschuh wrote:
> > > +struct cros_ec_hwmon_priv {
> > > +	struct cros_ec_device *cros_ec;
> > > +	const char *temp_sensor_names[EC_TEMP_SENSOR_ENTRIES + EC_TEMP_SENSOR_B_ENTRIES];
> > > +	u8 usable_fans;
> > > +};
> > > +
> > > +static int cros_ec_hwmon_read_fan_speed(struct cros_ec_device *cros_ec, u8 index, u16 *speed)
> > > +{
> > > +	u16 data;
> > > +	int ret;
> > > +
> > > +	ret = cros_ec_cmd_readmem(cros_ec, EC_MEMMAP_FAN + index * 2, 2, &data);
> > > +	if (ret < 0)
> > > +		return ret;
> > > +
> > > +	data = le16_to_cpu(data);
> > > +	*speed = data;
> > > +
> > > +	if (data == EC_FAN_SPEED_NOT_PRESENT || data == EC_FAN_SPEED_STALLED)
> > > +		return -EIO;
> > 
> > `data` could be eliminated; use `*speed` instead.
> 
> Then the le16 value would need to be written directly to the out
> parameter. The current usage relies on *speed (sometimes) being set even
> if ret != 0.
> 
> (See next response block)
> 
> > 
> > > +static int cros_ec_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
> > > +			      u32 attr, int channel, long *val)
> > > +{
> > [...]
> > > +	u16 speed = 0;
> > > +	u8 temp = 0;
> > 
> > They don't need to initialize.
> 
> They need to.
> 
> The logic
> 
> if (ret == -EIO && speed == EC_FAN_SPEED_STALLED)
> 	ret = 0;
> 
> relies on -EIO and a write to speed from cros_ec_hwmon_read_fan_speed().
> 
> But if cros_ec_cmd_readmem() already returns -EIO, then speed would be
> uninitialized.

I see.