[PATCH v4 0/4] some cleanup and fix in gpd-fan

[PATCH v4 0/4] some cleanup and fix in gpd-fan

[Pei Xiao]

changes in v4:
1. Add a missing sob in  
hwmon: (gpd-fan): drop global driver data and use per-device
    allocation

changes in v3:
1.All patches add v3 version tags

changes in v2:
1.Add a new patch for fix race condition between device removal and sysfs
access.
2.Platform_create_bundle pass a driver_data pointer 
3.gpd_init_ec needed before hwmon registration as a separate patch

Pei Xiao (4):
  hwmon: (gpd-fan): drop global driver data and use per-device
    allocation
  hwmon: (gpd-fan): Initialize EC before registering hwmon device
  hwmon: (gpd-fan): upgrade log level from warn to err for platform
    device creation failure
  hwmon: (gpd-fan): fix race condition between device removal and sysfs
    access

 drivers/hwmon/gpd-fan.c | 226 ++++++++++++++++++++++------------------
 1 file changed, 125 insertions(+), 101 deletions(-)

-- 
2.25.1

[PATCH v4 1/4] hwmon: (gpd-fan): drop global driver data and use per-device allocation

[Pei Xiao]

replace the global state gpd_driver_priv with per-device private data
(struct gpd_fan_data) allocated in probe. This allows the driver to
support multiple instances in the future and aligns with kernel best
practices.

No functional change intended.

Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
changes in v4:
1.Add a missing sob.

changes in v3:
1.Add v3 tag

changes in v2:
1.Platform_create_bundle pass a driver_data pointer
2.gpd_init_ec is needed before hwmon registration, submit as separate
bug fix.
---
 drivers/hwmon/gpd-fan.c | 209 ++++++++++++++++++++++------------------
 1 file changed, 115 insertions(+), 94 deletions(-)

diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
index 80de5f20781e..7284babd4f5c 100644
--- a/drivers/hwmon/gpd-fan.c
+++ b/drivers/hwmon/gpd-fan.c
@@ -40,12 +40,11 @@ enum FAN_PWM_ENABLE {
 	AUTOMATIC	= 2,
 };
 
-static struct {
+struct gpd_fan_data {
 	enum FAN_PWM_ENABLE pwm_enable;
 	u8 pwm_value;
-
 	const struct gpd_fan_drvdata *drvdata;
-} gpd_driver_priv;
+};
 
 struct gpd_fan_drvdata {
 	const char *board_name; // Board name for module param comparison
@@ -249,10 +248,10 @@ static const struct gpd_fan_drvdata *gpd_module_drvdata[] = {
 };
 
 // Helper functions to handle EC read/write
-static void gpd_ecram_read(u16 offset, u8 *val)
+static void gpd_ecram_read(const struct gpd_fan_drvdata *drvdata, u16 offset, u8 *val)
 {
-	u16 addr_port = gpd_driver_priv.drvdata->addr_port;
-	u16 data_port = gpd_driver_priv.drvdata->data_port;
+	u16 addr_port = drvdata->addr_port;
+	u16 data_port = drvdata->data_port;
 
 	outb(0x2E, addr_port);
 	outb(0x11, data_port);
@@ -270,10 +269,10 @@ static void gpd_ecram_read(u16 offset, u8 *val)
 	*val = inb(data_port);
 }
 
-static void gpd_ecram_write(u16 offset, u8 value)
+static void gpd_ecram_write(const struct gpd_fan_drvdata *drvdata, u16 offset, u8 value)
 {
-	u16 addr_port = gpd_driver_priv.drvdata->addr_port;
-	u16 data_port = gpd_driver_priv.drvdata->data_port;
+	u16 addr_port = drvdata->addr_port;
+	u16 data_port = drvdata->data_port;
 
 	outb(0x2E, addr_port);
 	outb(0x11, data_port);
@@ -291,198 +290,198 @@ static void gpd_ecram_write(u16 offset, u8 value)
 	outb(value, data_port);
 }
 
-static int gpd_generic_read_rpm(void)
+static int gpd_generic_read_rpm(struct gpd_fan_data *data)
 {
-	const struct gpd_fan_drvdata *const drvdata = gpd_driver_priv.drvdata;
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
 	u8 high, low;
 
-	gpd_ecram_read(drvdata->rpm_read, &high);
-	gpd_ecram_read(drvdata->rpm_read + 1, &low);
+	gpd_ecram_read(drvdata, drvdata->rpm_read, &high);
+	gpd_ecram_read(drvdata, drvdata->rpm_read + 1, &low);
 
 	return (u16)high << 8 | low;
 }
 
-static int gpd_wm2_read_rpm(void)
+static int gpd_wm2_read_rpm(struct gpd_fan_data *data)
 {
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
+
 	for (u16 pwm_ctr_offset = GPD_PWM_CTR_OFFSET;
 	     pwm_ctr_offset <= GPD_PWM_CTR_OFFSET + 2; pwm_ctr_offset++) {
 		u8 PWMCTR;
 
-		gpd_ecram_read(pwm_ctr_offset, &PWMCTR);
+		gpd_ecram_read(drvdata, pwm_ctr_offset, &PWMCTR);
 
 		if (PWMCTR != 0xB8)
-			gpd_ecram_write(pwm_ctr_offset, 0xB8);
+			gpd_ecram_write(drvdata, pwm_ctr_offset, 0xB8);
 	}
 
-	return gpd_generic_read_rpm();
+	return gpd_generic_read_rpm(data);
 }
 
 // Read value for fan1_input
-static int gpd_read_rpm(void)
+static int gpd_read_rpm(struct gpd_fan_data *data)
 {
-	switch (gpd_driver_priv.drvdata->board) {
+	switch (data->drvdata->board) {
 	case win4_6800u:
 	case win_mini:
 	case duo:
 	case mpc2:
-		return gpd_generic_read_rpm();
+		return gpd_generic_read_rpm(data);
 	case win_max_2:
-		return gpd_wm2_read_rpm();
+		return gpd_wm2_read_rpm(data);
 	}
 
 	return 0;
 }
 
-static int gpd_wm2_read_pwm(void)
+static int gpd_wm2_read_pwm(struct gpd_fan_data *data)
 {
-	const struct gpd_fan_drvdata *const drvdata = gpd_driver_priv.drvdata;
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
 	u8 var;
 
-	gpd_ecram_read(drvdata->pwm_write, &var);
+	gpd_ecram_read(drvdata, drvdata->pwm_write, &var);
 
 	// Match gpd_generic_write_pwm(u8) below
 	return DIV_ROUND_CLOSEST((var - 1) * 255, (drvdata->pwm_max - 1));
 }
 
 // Read value for pwm1
-static int gpd_read_pwm(void)
+static int gpd_read_pwm(struct gpd_fan_data *data)
 {
-	switch (gpd_driver_priv.drvdata->board) {
+	switch (data->drvdata->board) {
 	case win_mini:
 	case duo:
 	case win4_6800u:
 	case mpc2:
-		switch (gpd_driver_priv.pwm_enable) {
+		switch (data->pwm_enable) {
 		case DISABLE:
 			return 255;
 		case MANUAL:
-			return gpd_driver_priv.pwm_value;
+			return data->pwm_value;
 		case AUTOMATIC:
 			return -EOPNOTSUPP;
 		}
 		break;
 	case win_max_2:
-		return gpd_wm2_read_pwm();
+		return gpd_wm2_read_pwm(data);
 	}
 	return 0;
 }
 
 // PWM value's range in EC is 1 - pwm_max, cast 0 - 255 to it.
-static inline u8 gpd_cast_pwm_range(u8 val)
+static inline u8 gpd_cast_pwm_range(const struct gpd_fan_drvdata *drvdata, u8 val)
 {
-	const struct gpd_fan_drvdata *const drvdata = gpd_driver_priv.drvdata;
-
 	return DIV_ROUND_CLOSEST(val * (drvdata->pwm_max - 1), 255) + 1;
 }
 
-static void gpd_generic_write_pwm(u8 val)
+static void gpd_generic_write_pwm(struct gpd_fan_data *data, u8 val)
 {
-	const struct gpd_fan_drvdata *const drvdata = gpd_driver_priv.drvdata;
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
 	u8 pwm_reg;
 
-	pwm_reg = gpd_cast_pwm_range(val);
-	gpd_ecram_write(drvdata->pwm_write, pwm_reg);
+	pwm_reg = gpd_cast_pwm_range(drvdata, val);
+	gpd_ecram_write(drvdata, drvdata->pwm_write, pwm_reg);
 }
 
-static void gpd_duo_write_pwm(u8 val)
+static void gpd_duo_write_pwm(struct gpd_fan_data *data, u8 val)
 {
-	const struct gpd_fan_drvdata *const drvdata = gpd_driver_priv.drvdata;
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
 	u8 pwm_reg;
 
-	pwm_reg = gpd_cast_pwm_range(val);
-	gpd_ecram_write(drvdata->pwm_write, pwm_reg);
-	gpd_ecram_write(drvdata->pwm_write + 1, pwm_reg);
+	pwm_reg = gpd_cast_pwm_range(drvdata, val);
+	gpd_ecram_write(drvdata, drvdata->pwm_write, pwm_reg);
+	gpd_ecram_write(drvdata, drvdata->pwm_write + 1, pwm_reg);
 }
 
 // Write value for pwm1
-static int gpd_write_pwm(u8 val)
+static int gpd_write_pwm(struct gpd_fan_data *data, u8 val)
 {
-	if (gpd_driver_priv.pwm_enable != MANUAL)
+	if (data->pwm_enable != MANUAL)
 		return -EPERM;
 
-	switch (gpd_driver_priv.drvdata->board) {
+	switch (data->drvdata->board) {
 	case duo:
-		gpd_duo_write_pwm(val);
+		gpd_duo_write_pwm(data, val);
 		break;
 	case win_mini:
 	case win4_6800u:
 	case win_max_2:
 	case mpc2:
-		gpd_generic_write_pwm(val);
+		gpd_generic_write_pwm(data, val);
 		break;
 	}
 
 	return 0;
 }
 
-static void gpd_win_mini_set_pwm_enable(enum FAN_PWM_ENABLE pwm_enable)
+static void gpd_win_mini_set_pwm_enable(struct gpd_fan_data *data, enum FAN_PWM_ENABLE pwm_enable)
 {
 	switch (pwm_enable) {
 	case DISABLE:
-		gpd_generic_write_pwm(255);
+		gpd_generic_write_pwm(data, 255);
 		break;
 	case MANUAL:
-		gpd_generic_write_pwm(gpd_driver_priv.pwm_value);
+		gpd_generic_write_pwm(data, data->pwm_value);
 		break;
 	case AUTOMATIC:
-		gpd_ecram_write(gpd_driver_priv.drvdata->pwm_write, 0);
+		gpd_ecram_write(data->drvdata, data->drvdata->pwm_write, 0);
 		break;
 	}
 }
 
-static void gpd_duo_set_pwm_enable(enum FAN_PWM_ENABLE pwm_enable)
+static void gpd_duo_set_pwm_enable(struct gpd_fan_data *data, enum FAN_PWM_ENABLE pwm_enable)
 {
 	switch (pwm_enable) {
 	case DISABLE:
-		gpd_duo_write_pwm(255);
+		gpd_duo_write_pwm(data, 255);
 		break;
 	case MANUAL:
-		gpd_duo_write_pwm(gpd_driver_priv.pwm_value);
+		gpd_duo_write_pwm(data, data->pwm_value);
 		break;
 	case AUTOMATIC:
-		gpd_ecram_write(gpd_driver_priv.drvdata->pwm_write, 0);
+		gpd_ecram_write(data->drvdata, data->drvdata->pwm_write, 0);
 		break;
 	}
 }
 
-static void gpd_wm2_set_pwm_enable(enum FAN_PWM_ENABLE enable)
+static void gpd_wm2_set_pwm_enable(struct gpd_fan_data *data, enum FAN_PWM_ENABLE enable)
 {
-	const struct gpd_fan_drvdata *const drvdata = gpd_driver_priv.drvdata;
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
 
 	switch (enable) {
 	case DISABLE:
-		gpd_generic_write_pwm(255);
-		gpd_ecram_write(drvdata->manual_control_enable, 1);
+		gpd_generic_write_pwm(data, 255);
+		gpd_ecram_write(drvdata, drvdata->manual_control_enable, 1);
 		break;
 	case MANUAL:
-		gpd_generic_write_pwm(gpd_driver_priv.pwm_value);
-		gpd_ecram_write(drvdata->manual_control_enable, 1);
+		gpd_generic_write_pwm(data, data->pwm_value);
+		gpd_ecram_write(drvdata, drvdata->manual_control_enable, 1);
 		break;
 	case AUTOMATIC:
-		gpd_ecram_write(drvdata->manual_control_enable, 0);
+		gpd_ecram_write(drvdata, drvdata->manual_control_enable, 0);
 		break;
 	}
 }
 
 // Write value for pwm1_enable
-static void gpd_set_pwm_enable(enum FAN_PWM_ENABLE enable)
+static void gpd_set_pwm_enable(struct gpd_fan_data *data, enum FAN_PWM_ENABLE enable)
 {
 	if (enable == MANUAL)
 		// Set pwm_value to max firstly when switching to manual mode, in
 		// consideration of device safety.
-		gpd_driver_priv.pwm_value = 255;
+		data->pwm_value = 255;
 
-	switch (gpd_driver_priv.drvdata->board) {
+	switch (data->drvdata->board) {
 	case win_mini:
 	case win4_6800u:
 	case mpc2:
-		gpd_win_mini_set_pwm_enable(enable);
+		gpd_win_mini_set_pwm_enable(data, enable);
 		break;
 	case duo:
-		gpd_duo_set_pwm_enable(enable);
+		gpd_duo_set_pwm_enable(data, enable);
 		break;
 	case win_max_2:
-		gpd_wm2_set_pwm_enable(enable);
+		gpd_wm2_set_pwm_enable(data, enable);
 		break;
 	}
 }
@@ -505,15 +504,16 @@ static umode_t gpd_fan_hwmon_is_visible(__always_unused const void *drvdata,
 	return 0;
 }
 
-static int gpd_fan_hwmon_read(__always_unused struct device *dev,
+static int gpd_fan_hwmon_read(struct device *dev,
 			      enum hwmon_sensor_types type, u32 attr,
 			      __always_unused int channel, long *val)
 {
+	struct gpd_fan_data *data = dev_get_drvdata(dev);
 	int ret;
 
 	if (type == hwmon_fan) {
 		if (attr == hwmon_fan_input) {
-			ret = gpd_read_rpm();
+			ret = gpd_read_rpm(data);
 
 			if (ret < 0)
 				return ret;
@@ -524,10 +524,10 @@ static int gpd_fan_hwmon_read(__always_unused struct device *dev,
 	} else if (type == hwmon_pwm) {
 		switch (attr) {
 		case hwmon_pwm_enable:
-			*val = gpd_driver_priv.pwm_enable;
+			*val = data->pwm_enable;
 			return 0;
 		case hwmon_pwm_input:
-			ret = gpd_read_pwm();
+			ret = gpd_read_pwm(data);
 
 			if (ret < 0)
 				return ret;
@@ -540,27 +540,29 @@ static int gpd_fan_hwmon_read(__always_unused struct device *dev,
 	return -EOPNOTSUPP;
 }
 
-static int gpd_fan_hwmon_write(__always_unused struct device *dev,
+static int gpd_fan_hwmon_write(struct device *dev,
 			       enum hwmon_sensor_types type, u32 attr,
 			       __always_unused int channel, long val)
 {
+	struct gpd_fan_data *data = dev_get_drvdata(dev);
+
 	if (type == hwmon_pwm) {
 		switch (attr) {
 		case hwmon_pwm_enable:
 			if (!in_range(val, 0, 3))
 				return -EINVAL;
 
-			gpd_driver_priv.pwm_enable = val;
+			data->pwm_enable = val;
 
-			gpd_set_pwm_enable(gpd_driver_priv.pwm_enable);
+			gpd_set_pwm_enable(data, data->pwm_enable);
 			return 0;
 		case hwmon_pwm_input:
 			if (!in_range(val, 0, 256))
 				return -EINVAL;
 
-			gpd_driver_priv.pwm_value = val;
+			data->pwm_value = val;
 
-			return gpd_write_pwm(val);
+			return gpd_write_pwm(data, val);
 		}
 	}
 
@@ -584,26 +586,27 @@ static struct hwmon_chip_info gpd_fan_chip_info = {
 	.info = gpd_fan_hwmon_channel_info
 };
 
-static void gpd_win4_init_ec(void)
+static void gpd_win4_init_ec(struct gpd_fan_data *data)
 {
+	const struct gpd_fan_drvdata *drvdata = data->drvdata;
 	u8 chip_id, chip_ver;
 
-	gpd_ecram_read(0x2000, &chip_id);
+	gpd_ecram_read(drvdata, 0x2000, &chip_id);
 
 	if (chip_id == 0x55) {
-		gpd_ecram_read(0x1060, &chip_ver);
-		gpd_ecram_write(0x1060, chip_ver | 0x80);
+		gpd_ecram_read(drvdata, 0x1060, &chip_ver);
+		gpd_ecram_write(drvdata, 0x1060, chip_ver | 0x80);
 	}
 }
 
-static void gpd_init_ec(void)
+static void gpd_init_ec(struct gpd_fan_data *data)
 {
 	// The buggy firmware won't initialize EC properly on boot.
 	// Before its initialization, reading RPM will always return 0,
 	// and writing PWM will have no effect.
 	// Initialize it manually on driver load.
-	if (gpd_driver_priv.drvdata->board == win4_6800u)
-		gpd_win4_init_ec();
+	if (data->drvdata->board == win4_6800u)
+		gpd_win4_init_ec(data);
 }
 
 static int gpd_fan_probe(struct platform_device *pdev)
@@ -611,7 +614,9 @@ static int gpd_fan_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	const struct resource *region;
 	const struct resource *res;
-	const struct device *hwdev;
+	struct device *hwdev;
+	struct gpd_fan_data *data;
+	const struct gpd_fan_drvdata *match;
 
 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
 	if (!res)
@@ -624,24 +629,42 @@ static int gpd_fan_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, -EBUSY,
 				     "Failed to request region\n");
 
+	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	match = dev_get_platdata(dev);
+	if (!match)
+		return -EINVAL;
+
+	data->drvdata = match;
+	data->pwm_enable = AUTOMATIC;
+	data->pwm_value = 255;
+
+	dev_set_drvdata(dev, data);
+
 	hwdev = devm_hwmon_device_register_with_info(dev,
 						     DRIVER_NAME,
-						     NULL,
+						     data,
 						     &gpd_fan_chip_info,
 						     NULL);
 	if (IS_ERR(hwdev))
 		return dev_err_probe(dev, PTR_ERR(hwdev),
 				     "Failed to register hwmon device\n");
 
-	gpd_init_ec();
+	gpd_init_ec(data);
 
 	return 0;
 }
 
-static void gpd_fan_remove(__always_unused struct platform_device *pdev)
+static void gpd_fan_remove(struct platform_device *pdev)
 {
-	gpd_driver_priv.pwm_enable = AUTOMATIC;
-	gpd_set_pwm_enable(AUTOMATIC);
+	struct gpd_fan_data *data = dev_get_drvdata(&pdev->dev);
+
+	if (data) {
+		data->pwm_enable = AUTOMATIC;
+		gpd_set_pwm_enable(data, AUTOMATIC);
+	}
 }
 
 static struct platform_driver gpd_fan_driver = {
@@ -668,6 +691,7 @@ static int __init gpd_fan_init(void)
 	if (!match) {
 		const struct dmi_system_id *dmi_match =
 			dmi_first_match(dmi_table);
+
 		if (dmi_match)
 			match = dmi_match->driver_data;
 	}
@@ -675,10 +699,6 @@ static int __init gpd_fan_init(void)
 	if (!match)
 		return -ENODEV;
 
-	gpd_driver_priv.pwm_enable = AUTOMATIC;
-	gpd_driver_priv.pwm_value = 255;
-	gpd_driver_priv.drvdata = match;
-
 	struct resource gpd_fan_resources[] = {
 		{
 			.start = match->addr_port,
@@ -690,7 +710,8 @@ static int __init gpd_fan_init(void)
 	gpd_fan_platform_device = platform_create_bundle(&gpd_fan_driver,
 							 gpd_fan_probe,
 							 gpd_fan_resources,
-							 1, NULL, 0);
+							 1,
+							 match, sizeof(*match));
 
 	if (IS_ERR(gpd_fan_platform_device)) {
 		pr_warn("Failed to create platform device\n");
-- 
2.25.1

Re: [PATCH v4 1/4] hwmon: (gpd-fan): drop global driver data and use per-device allocation

[sashiko-bot]

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

Pre-existing issues:
- [High] Software state initialization in `probe()` is not synchronized with actual hardware state.
--

commit 072171983894d237c762c5fb521a8b93d2504d1f
Author: Pei Xiao <xiaopei01@kylinos.cn>

hwmon: (gpd-fan): drop global driver data and use per-device allocation

This patch replaces the global state gpd_driver_priv with per-device private
data (struct gpd_fan_data) allocated during probe. This allows the driver to
support multiple instances in the future and aligns with kernel best practices.

> diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
> index 80de5f20781eb..7284babd4f5c9 100644
> --- a/drivers/hwmon/gpd-fan.c
> +++ b/drivers/hwmon/gpd-fan.c

[ ... ]

> @@ -624,24 +629,42 @@ static int gpd_fan_probe(struct platform_device *pdev)
>  		return dev_err_probe(dev, -EBUSY,
>  				     "Failed to request region\n");
>  
> +	data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> +	if (!data)
> +		return -ENOMEM;
> +
> +	match = dev_get_platdata(dev);
> +	if (!match)
> +		return -EINVAL;
> +
> +	data->drvdata = match;
> +	data->pwm_enable = AUTOMATIC;
> +	data->pwm_value = 255;
> +
> +	dev_set_drvdata(dev, data);
> +

[Severity: High]
This is a pre-existing issue, but I noticed that while the software state
for pwm_enable is initialized to AUTOMATIC here in gpd_fan_probe(), there
doesn't appear to be a corresponding write to the hardware EC to actually
set this mode.

If the fan was left in manual mode by a previous driver instance, a crash,
or the BIOS, won't it remain stuck at a fixed speed while the sysfs interface
reports automatic to userspace?

Could this mismatch cause OS thermal management daemons to falsely assume
the hardware is dynamically managing the fan, potentially leading to silent
thermal throttling or shutdowns under heavy load?

>  	hwdev = devm_hwmon_device_register_with_info(dev,
>  						     DRIVER_NAME,
> -						     NULL,
> +						     data,
>  						     &gpd_fan_chip_info,
>  						     NULL);
>  	if (IS_ERR(hwdev))
>  		return dev_err_probe(dev, PTR_ERR(hwdev),
>  				     "Failed to register hwmon device\n");
>  
> -	gpd_init_ec();
> +	gpd_init_ec(data);
>  
>  	return 0;
>  }

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1781055639.git.xiaopei01@kylinos.cn?part=1

Re: [PATCH v4 1/4] hwmon: (gpd-fan): drop global driver data and use per-device allocation

[Guenter Roeck]

On Wed, Jun 10, 2026 at 09:49:09AM +0800, Pei Xiao wrote:
> replace the global state gpd_driver_priv with per-device private data
> (struct gpd_fan_data) allocated in probe. This allows the driver to
> support multiple instances in the future and aligns with kernel best
> practices.
> 
> No functional change intended.
> 
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

Applied.

Thanks,
Guenter

[PATCH v4 2/4] hwmon: (gpd-fan): Initialize EC before registering hwmon device

[Pei Xiao]

Move the gpd_init_ec() call to before devm_hwmon_device_register_with_info
in the probe function. With the previous ordering the hwmon device was
registered and exposed to userspace before the EC initialization
completes, creating a window where sysfs reads could return invalid values.

Some buggy firmware won't initialize EC properly on boot. Before its
initialization, reading RPM will always return 0, and writing PWM will have
no effect. So move gpd_init_ec to before hwmon device register.

Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
changes in v4:
No changes

changes in v3:
1.Add v3 tag

changes in v2:
1.gpd_init_ec needed before hwmon registration, as separate bug fix
---
 drivers/hwmon/gpd-fan.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
index 7284babd4f5c..745b3fb9e3a4 100644
--- a/drivers/hwmon/gpd-fan.c
+++ b/drivers/hwmon/gpd-fan.c
@@ -643,6 +643,7 @@ static int gpd_fan_probe(struct platform_device *pdev)
 
 	dev_set_drvdata(dev, data);
 
+	gpd_init_ec(data);
 	hwdev = devm_hwmon_device_register_with_info(dev,
 						     DRIVER_NAME,
 						     data,
@@ -651,9 +652,6 @@ static int gpd_fan_probe(struct platform_device *pdev)
 	if (IS_ERR(hwdev))
 		return dev_err_probe(dev, PTR_ERR(hwdev),
 				     "Failed to register hwmon device\n");
-
-	gpd_init_ec(data);
-
 	return 0;
 }
 
-- 
2.25.1

Re: [PATCH v4 2/4] hwmon: (gpd-fan): Initialize EC before registering hwmon device

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:

Pre-existing issues:
- [High] Reading the PWM value causes an arithmetic underflow and returns a negative error code when the hardware value is 0.
- [High] The driver permanently claims standard globally multiplexed Super I/O ports using `devm_request_region()`, breaking x86 concurrency and causing a Denial of Service for other drivers.
- [High] Missing suspend/resume power management callbacks to re-initialize the EC state after system sleep.
--

commit 5f38d453c010b9c77f2e24db2a05033fcf65d138
Author: Pei Xiao <xiaopei01@kylinos.cn>

hwmon: (gpd-fan): Initialize EC before registering hwmon device

The commit moves the gpd_init_ec() call to happen before registering
the hwmon device. This prevents a window where sysfs reads could
return invalid values if the EC is not yet initialized.

> diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
> index 7284babd4f5c9..745b3fb9e3a49 100644
> --- a/drivers/hwmon/gpd-fan.c
> +++ b/drivers/hwmon/gpd-fan.c
> @@ -643,6 +643,7 @@ static int gpd_fan_probe(struct platform_device *pdev)
>  
>  	dev_set_drvdata(dev, data);
>  
> +	gpd_init_ec(data);

[Severity: High]
This isn't a bug introduced by this patch, but since we are initializing the
EC here due to buggy firmware losing its state, does the EC also lose its
state across system sleep transitions?

Looking at gpd_fan_driver, the platform driver is missing power management
callbacks (pm_ops) for suspend and resume. When the system returns from
S3 suspend-to-RAM, will the EC return to an uninitialized state and silently
break thermal fan control since there is no resume hook to re-invoke
gpd_init_ec()?

Also, this is a pre-existing issue, but does using devm_request_region() in
gpd_fan_probe() permanently claim the globally multiplexed Super I/O ports
(0x2E-0x2F or 0x4E-0x4F)?

These ports are heavily shared across the motherboard. Standard practice is to
lock them dynamically for a single transaction using request_muxed_region(). By
locking them permanently via devm_request_region(), does this prevent other
drivers from claiming the multiplexer and cause them to fail probing?

Additionally, when interacting with these ports in gpd_ecram_read() and
gpd_ecram_write(), the multi-step outb/inb sequences are executed without any
locking. Could this race dangerously with other subsystems or ACPI?

>  	hwdev = devm_hwmon_device_register_with_info(dev,
>  						     DRIVER_NAME,
>  						     data,
>  						     &gpd_fan_chip_info,
>  						     NULL);
>  	if (IS_ERR(hwdev))
>  		return dev_err_probe(dev, PTR_ERR(hwdev),
>  				     "Failed to register hwmon device\n");
> -
> -	gpd_init_ec(data);
> -
>  	return 0;
>  }

[Severity: High]
This is a pre-existing issue, but could the calculation in gpd_wm2_read_pwm()
underflow and propagate a negative error code to userspace?

drivers/hwmon/gpd-fan.c:gpd_wm2_read_pwm() {
	...
	u8 var;

	gpd_ecram_read(drvdata, drvdata->pwm_write, &var);

	// Match gpd_generic_write_pwm(u8) below
	return DIV_ROUND_CLOSEST((var - 1) * 255, (drvdata->pwm_max - 1));
}

If the hardware returns a PWM value of 0, (var - 1) promotes to a signed integer
and evaluates to -1. Multiplying by 255 and dividing propagates this negative
result, causing the function to return a negative value, which is then reported
to userspace as a negative error code (e.g., -EPERM) instead of gracefully
reporting a valid 0 PWM state.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1781055639.git.xiaopei01@kylinos.cn?part=2

Re: [PATCH v4 2/4] hwmon: (gpd-fan): Initialize EC before registering hwmon device

[Guenter Roeck]

On Wed, Jun 10, 2026 at 09:49:10AM +0800, Pei Xiao wrote:
> Move the gpd_init_ec() call to before devm_hwmon_device_register_with_info
> in the probe function. With the previous ordering the hwmon device was
> registered and exposed to userspace before the EC initialization
> completes, creating a window where sysfs reads could return invalid values.
> 
> Some buggy firmware won't initialize EC properly on boot. Before its
> initialization, reading RPM will always return 0, and writing PWM will have
> no effect. So move gpd_init_ec to before hwmon device register.
> 
> Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

Applied.

Thanks,
Guenter

[PATCH v4 3/4] hwmon: (gpd-fan): upgrade log level from warn to err for platform device creation failure

[Pei Xiao]

When platform_create_bundle() fails, the error is fatal and prevents the
driver from loading. Use pr_err() instead of pr_warn() to clearly indicate
a critical failure.

Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
changes in v4:
No changes.

changes in v3:
1.Add v3 tag.

changes in v2:
1.No changes.
---
 drivers/hwmon/gpd-fan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
index 745b3fb9e3a4..1b57a5add934 100644
--- a/drivers/hwmon/gpd-fan.c
+++ b/drivers/hwmon/gpd-fan.c
@@ -712,7 +712,7 @@ static int __init gpd_fan_init(void)
 							 match, sizeof(*match));
 
 	if (IS_ERR(gpd_fan_platform_device)) {
-		pr_warn("Failed to create platform device\n");
+		pr_err("Failed to create platform device\n");
 		return PTR_ERR(gpd_fan_platform_device);
 	}
 
-- 
2.25.1

Re: [PATCH v4 3/4] hwmon: (gpd-fan): upgrade log level from warn to err for platform device creation failure

[sashiko-bot]

> When platform_create_bundle() fails, the error is fatal and prevents the
> driver from loading. Use pr_err() instead of pr_warn() to clearly indicate
> a critical failure.
> 
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

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

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1781055639.git.xiaopei01@kylinos.cn?part=3

Re: [PATCH v4 3/4] hwmon: (gpd-fan): upgrade log level from warn to err for platform device creation failure

[Guenter Roeck]

On Wed, Jun 10, 2026 at 09:49:11AM +0800, Pei Xiao wrote:
> When platform_create_bundle() fails, the error is fatal and prevents the
> driver from loading. Use pr_err() instead of pr_warn() to clearly indicate
> a critical failure.
> 
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

Applied.

Thanks,
Guenter

[PATCH v4 4/4] hwmon: (gpd-fan): fix race condition between device removal and sysfs access

[Pei Xiao]

Replace the manual gpd_fan_remove() callback with a devres-managed
action using devm_add_action_or_reset(). The original remove hook
resets the fan to AUTOMATIC mode, but the hwmon sysfs interface
(registered with devm_hwmon_device_register_with_info()) remains
active until after the remove callback completes. This creates a
race window where a concurrent userspace sysfs access can interleave
with the EC I/O sequence, potentially corrupting EC registers.

Using devm_add_action_or_reset() registers the reset function as a
devres action. Due to the LIFO release order of devres, the hwmon
device is unregistered (sysfs removed) before the reset action
executes, eliminating the race condition.

Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>
---
changes in v4:
No changes.

changes in v3:
1.Add v3 tag

changes in v2:
1.Fix a race condition between device removal and sysfs access report by
sashiko-bot
---
 drivers/hwmon/gpd-fan.c | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/drivers/hwmon/gpd-fan.c b/drivers/hwmon/gpd-fan.c
index 1b57a5add934..d1993cd645cb 100644
--- a/drivers/hwmon/gpd-fan.c
+++ b/drivers/hwmon/gpd-fan.c
@@ -609,6 +609,16 @@ static void gpd_init_ec(struct gpd_fan_data *data)
 		gpd_win4_init_ec(data);
 }
 
+static void gpd_fan_reset_hardware(void *pdata)
+{
+	struct gpd_fan_data *data = pdata;
+
+	if (data) {
+		data->pwm_enable = AUTOMATIC;
+		gpd_set_pwm_enable(data, AUTOMATIC);
+	}
+}
+
 static int gpd_fan_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -617,6 +627,7 @@ static int gpd_fan_probe(struct platform_device *pdev)
 	struct device *hwdev;
 	struct gpd_fan_data *data;
 	const struct gpd_fan_drvdata *match;
+	int ret;
 
 	res = platform_get_resource(pdev, IORESOURCE_IO, 0);
 	if (!res)
@@ -644,6 +655,11 @@ static int gpd_fan_probe(struct platform_device *pdev)
 	dev_set_drvdata(dev, data);
 
 	gpd_init_ec(data);
+
+	ret = devm_add_action_or_reset(dev, gpd_fan_reset_hardware, data);
+	if (ret)
+		return ret;
+
 	hwdev = devm_hwmon_device_register_with_info(dev,
 						     DRIVER_NAME,
 						     data,
@@ -655,19 +671,8 @@ static int gpd_fan_probe(struct platform_device *pdev)
 	return 0;
 }
 
-static void gpd_fan_remove(struct platform_device *pdev)
-{
-	struct gpd_fan_data *data = dev_get_drvdata(&pdev->dev);
-
-	if (data) {
-		data->pwm_enable = AUTOMATIC;
-		gpd_set_pwm_enable(data, AUTOMATIC);
-	}
-}
-
 static struct platform_driver gpd_fan_driver = {
 	.probe = gpd_fan_probe,
-	.remove = gpd_fan_remove,
 	.driver = {
 		.name = KBUILD_MODNAME,
 	},
-- 
2.25.1

Re: [PATCH v4 4/4] hwmon: (gpd-fan): fix race condition between device removal and sysfs access

[sashiko-bot]

> Replace the manual gpd_fan_remove() callback with a devres-managed
> action using devm_add_action_or_reset(). The original remove hook
> resets the fan to AUTOMATIC mode, but the hwmon sysfs interface
> (registered with devm_hwmon_device_register_with_info()) remains
> active until after the remove callback completes. This creates a
> race window where a concurrent userspace sysfs access can interleave
> with the EC I/O sequence, potentially corrupting EC registers.
> 
> Using devm_add_action_or_reset() registers the reset function as a
> devres action. Due to the LIFO release order of devres, the hwmon
> device is unregistered (sysfs removed) before the reset action
> executes, eliminating the race condition.
> 
> Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

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

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/cover.1781055639.git.xiaopei01@kylinos.cn?part=4

Re: [PATCH v4 4/4] hwmon: (gpd-fan): fix race condition between device removal and sysfs access

[Guenter Roeck]

On Wed, Jun 10, 2026 at 09:49:12AM +0800, Pei Xiao wrote:
> Replace the manual gpd_fan_remove() callback with a devres-managed
> action using devm_add_action_or_reset(). The original remove hook
> resets the fan to AUTOMATIC mode, but the hwmon sysfs interface
> (registered with devm_hwmon_device_register_with_info()) remains
> active until after the remove callback completes. This creates a
> race window where a concurrent userspace sysfs access can interleave
> with the EC I/O sequence, potentially corrupting EC registers.
> 
> Using devm_add_action_or_reset() registers the reset function as a
> devres action. Due to the LIFO release order of devres, the hwmon
> device is unregistered (sysfs removed) before the reset action
> executes, eliminating the race condition.
> 
> Fixes: 0ab88e239439 ("hwmon: add GPD devices sensor driver")
> Signed-off-by: Pei Xiao <xiaopei01@kylinos.cn>

Applied.

Thanks,
Guenter