Message-ID: <767538f2-d79e-44e4-a671-4be56a3cfe44@roeck-us.net>
Date: Wed, 5 Feb 2025 10:01:20 -0800
From: Guenter Roeck <linux@...ck-us.net>
To: Werner Sembach <wse@...edocomputers.com>, hdegoede@...hat.com,
 ilpo.jarvinen@...ux.intel.com, ukleinek@...nel.org, jdelvare@...e.com
Cc: linux-kernel@...r.kernel.org, platform-driver-x86@...r.kernel.org,
 linux-pwm@...r.kernel.org, linux-hwmon@...r.kernel.org
Subject: Re: [RFC PATCH 1/1] platform/x86/tuxedo: Implement TUXEDO TUXI ACPI
 TFAN via hwmon

On 2/5/25 08:19, Werner Sembach wrote:
> The TUXEDO Sirius 16 Gen1 & Gen2 have the custom TUXEDO Interface (TUXI)
> ACPI interface which currently consists of the TFAN device. This has ACPI
> functions to control the built in fans and monitor fan speeds and CPU and
> GPU temprature.
> 
> This driver implements this TFAN device via the hwmon subsystem with an
> added temprature check that ensure a minimum fanspeed at certain
> tempratures. This allows userspace controlled, but hardware safe, custom
> fan curves.
> 
> Signed-off-by: Werner Sembach <wse@...edocomputers.com>
> ---
>   MAINTAINERS                                   |   6 +
>   drivers/platform/x86/Kconfig                  |   2 +
>   drivers/platform/x86/Makefile                 |   3 +
>   drivers/platform/x86/tuxedo/Kbuild            |   6 +
>   drivers/platform/x86/tuxedo/Kconfig           |   6 +
>   drivers/platform/x86/tuxedo/nbxx/Kbuild       |   9 +
>   drivers/platform/x86/tuxedo/nbxx/Kconfig      |  13 +
>   .../x86/tuxedo/nbxx/acpi_tuxi_hwmon.c         | 421 ++++++++++++++++++
>   .../x86/tuxedo/nbxx/acpi_tuxi_hwmon.h         |  14 +
>   .../platform/x86/tuxedo/nbxx/acpi_tuxi_init.c |  60 +++
>   .../platform/x86/tuxedo/nbxx/acpi_tuxi_init.h |  16 +
>   .../platform/x86/tuxedo/nbxx/acpi_tuxi_util.c |  58 +++
>   .../platform/x86/tuxedo/nbxx/acpi_tuxi_util.h |  84 ++++
>   13 files changed, 698 insertions(+)
>   create mode 100644 drivers/platform/x86/tuxedo/Kbuild
>   create mode 100644 drivers/platform/x86/tuxedo/Kconfig
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/Kbuild
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/Kconfig
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.c
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.h
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.c
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.h
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.c
>   create mode 100644 drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 0fa7c5728f1e6..2d3fe9de4e9cf 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -23916,6 +23916,12 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux.git turbostat
>   F:	tools/power/x86/turbostat/
>   F:	tools/testing/selftests/turbostat/
>   
> +TUXEDO DRIVERS
> +M:	Werner Sembach <wse@...edocomputers.com>
> +L:	platform-driver-x86@...r.kernel.org
> +S:	Supported
> +F:	drivers/platform/x86/tuxedo/
> +
>   TW5864 VIDEO4LINUX DRIVER
>   M:	Bluecherry Maintainers <maintainers@...echerrydvr.com>
>   M:	Andrey Utkin <andrey.utkin@...p.bluecherry.net>
> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
> index 0258dd879d64b..9b78a1255c08e 100644
> --- a/drivers/platform/x86/Kconfig
> +++ b/drivers/platform/x86/Kconfig
> @@ -1199,3 +1199,5 @@ config P2SB
>   	  The main purpose of this library is to unhide P2SB device in case
>   	  firmware kept it hidden on some platforms in order to access devices
>   	  behind it.
> +
> +source "drivers/platform/x86/tuxedo/Kconfig"
> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
> index e1b1429470674..1562dcd7ad9a5 100644
> --- a/drivers/platform/x86/Makefile
> +++ b/drivers/platform/x86/Makefile
> @@ -153,3 +153,6 @@ obj-$(CONFIG_WINMATE_FM07_KEYS)		+= winmate-fm07-keys.o
>   
>   # SEL
>   obj-$(CONFIG_SEL3350_PLATFORM)		+= sel3350-platform.o
> +
> +# TUXEDO
> +obj-y					+= tuxedo/
> diff --git a/drivers/platform/x86/tuxedo/Kbuild b/drivers/platform/x86/tuxedo/Kbuild
> new file mode 100644
> index 0000000000000..0de6c7871db95
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/Kbuild
> @@ -0,0 +1,6 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +#
> +# TUXEDO X86 Platform Specific Drivers
> +#
> +
> +obj-y	+= nbxx/
> diff --git a/drivers/platform/x86/tuxedo/Kconfig b/drivers/platform/x86/tuxedo/Kconfig
> new file mode 100644
> index 0000000000000..82df7419cf29d
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/Kconfig
> @@ -0,0 +1,6 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +#
> +# TUXEDO X86 Platform Specific Drivers
> +#
> +
> +source "drivers/platform/x86/tuxedo/nb04/Kconfig"
> diff --git a/drivers/platform/x86/tuxedo/nbxx/Kbuild b/drivers/platform/x86/tuxedo/nbxx/Kbuild
> new file mode 100644
> index 0000000000000..db8def8ffe8f6
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/Kbuild
> @@ -0,0 +1,9 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +#
> +# TUXEDO X86 Platform Specific Drivers
> +#
> +
> +tuxedo_nbxx_acpi_tuxi-y			:= acpi_tuxi_init.o
> +tuxedo_nbxx_acpi_tuxi-y			+= acpi_tuxi_util.o
> +tuxedo_nbxx_acpi_tuxi-y			+= acpi_tuxi_hwmon.o
> +obj-$(CONFIG_TUXEDO_NBXX_ACPI_TUXI)	+= tuxedo_nbxx_acpi_tuxi.o
> diff --git a/drivers/platform/x86/tuxedo/nbxx/Kconfig b/drivers/platform/x86/tuxedo/nbxx/Kconfig
> new file mode 100644
> index 0000000000000..827c65c410fb2
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/Kconfig
> @@ -0,0 +1,13 @@
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +#
> +# TUXEDO X86 Platform Specific Drivers
> +#
> +
> +config TUXEDO_NBXX_ACPI_TUXI
> +	tristate "TUXEDO NBxx ACPI TUXI Platform Driver"
> +	help
> +	  This driver implements the ACPI TUXI device found on some TUXEDO
> +	  Notebooks. Currently this consists only of the TFAN subdevice which is
> +	  implemented via hwmon.
> +
> +	  When compiled as a module it will be called tuxedo_nbxx_acpi_tuxi
> diff --git a/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.c b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.c
> new file mode 100644
> index 0000000000000..8ebb2bfc19e20
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.c
> @@ -0,0 +1,421 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2024-2025 Werner Sembach wse@...edocomputers.com
> + */
> +
> +#include <linux/array_size.h>
> +#include <linux/hwmon.h>
> +#include <linux/workqueue.h>
> +
> +#include "acpi_tuxi_util.h"
> +
> +#include "acpi_tuxi_hwmon.h"
> +
> +struct tuxi_hwmon_driver_data_t {
> +	struct delayed_work work;
> +	struct device *hwmdev;
> +	u8 fan_count;
> +	const char **fan_types;
> +	u8 *temp_level;
> +	u8 *curr_speed;
> +	u8 *want_speed;
> +	u8 pwm_enabled;

Pretty much all those variables are not range checked when assigned.
I commented on one of them below, but it pretty much applies everywhere.
Overflows will have some interesting results.

> +};
> +
> +struct tuxi_temp_high_config_t {
> +	long temp;
> +	u8 min_speed;
> +};
> +
> +#define TUXI_SAFEGUARD_PERIOD 1000
> +
> +#define TUXI_PWM_FAN_ON_MIN_SPEED 0x40 // ~25%
> +
> +static struct tuxi_temp_high_config_t temp_levels[] = {
> +	{  80000, 0x4d }, // ~30%
> +	{  90000, 0x66 }, // ~40%
> +	{  95000, 0x99 }, // ~60%
> +	{ 100000, 0xff }, // 100%
> +	{ }
> +};
> +
> +static umode_t hwm_is_visible(const void * __always_unused data,
> +			      enum hwmon_sensor_types type,
> +			      u32 __always_unused attr,
> +			      int __always_unused channel)
> +{
> +	switch (type) {
> +	case hwmon_fan:
> +		return 0444;
> +	case hwmon_pwm:
> +		return 0644;
> +	case hwmon_temp:
> +		return 0444;
> +	default:
> +		break;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static int hwm_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +		    int channel, long *val)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data = dev_get_drvdata(dev);
> +	struct acpi_device *pdev = to_acpi_device(dev->parent);
> +	int ret;
> +
> +	unsigned long long params[2];
> +	unsigned long long retval;
> +
> +	switch (type) {
> +	case hwmon_fan:
> +		params[0] = channel;
> +		ret = tuxi_tfan_method(pdev,
> +				       TUXI_TFAN_METHOD_GET_FAN_RPM,
> +				       params, 1, &retval);
> +		*val = retval;
> +		return ret;
> +	case hwmon_pwm:
> +		switch (attr) {
> +		case hwmon_pwm_input:
> +			if (driver_data->pwm_enabled) {
> +				*val = driver_data->curr_speed[channel];
> +				return 0;
> +			}
> +			params[0] = channel;
> +			ret = tuxi_tfan_method(pdev,
> +					       TUXI_TFAN_METHOD_GET_FAN_SPEED,
> +					       params, 1, &retval);
> +			*val = retval;
> +			return ret;
> +		case hwmon_pwm_enable:
> +			*val = driver_data->pwm_enabled;
> +			return ret;
> +		}
> +		break;
> +	case hwmon_temp:
> +		params[0] = channel;
> +		ret = tuxi_tfan_method(pdev,
> +				       TUXI_TFAN_METHOD_GET_FAN_TEMPERATURE,
> +				       params, 1, &retval);
> +		*val = retval * 100 - 272000;
> +		return ret;
> +	default:
> +		break;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static int hwm_read_string(struct device *dev,
> +			   enum hwmon_sensor_types __always_unused type,
> +			   u32 __always_unused attr, int channel,
> +			   const char **str)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data = dev_get_drvdata(dev);
> +
> +	*str = driver_data->fan_types[channel];
> +
> +	return 0;
> +}
> +
> +static int write_speed(struct device *dev, int channel, long val)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data = dev_get_drvdata(dev);
> +	struct acpi_device *pdev = to_acpi_device(dev->parent);
> +	int ret;
> +
> +	unsigned long long params[2];
> +
> +	params[0] = channel;
> +
> +	u8 temp_level, min_speed;
> +
> +	temp_level = driver_data->temp_level[channel];
> +	if (temp_level) {
> +		min_speed = temp_levels[temp_level].min_speed;
> +		if (val < min_speed)
> +			val = min_speed;
> +	}
> +
> +	if (val < TUXI_PWM_FAN_ON_MIN_SPEED / 2)
> +		params[1] = 0;
> +	else if (val < TUXI_PWM_FAN_ON_MIN_SPEED)
> +		params[1] = TUXI_PWM_FAN_ON_MIN_SPEED;
> +	else
> +		params[1] = val;
> +
> +	ret = tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_SET_FAN_SPEED,
> +			       params, 2, NULL);
> +	if (ret)
> +		return ret;
> +
> +	driver_data->curr_speed[channel] = val;
> +
> +	return 0;
> +}
> +
> +static int hwm_write(struct device *dev,
> +		     enum hwmon_sensor_types __always_unused type, u32 attr,
> +		     int channel, long val)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data = dev_get_drvdata(dev);
> +	struct acpi_device *pdev = to_acpi_device(dev->parent);
> +	unsigned int i;
> +	int ret;
> +
> +	unsigned long long params[2];
> +
> +	switch (attr) {
> +	case hwmon_pwm_input:
> +		if (driver_data->pwm_enabled) {
> +			driver_data->want_speed[channel] = val;
> +			return write_speed(dev, channel, val);
> +		}
> +
> +		return 0;
> +	case hwmon_pwm_enable:
> +		params[0] = val;
> +		ret = tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_SET_FAN_MODE,
> +				       params, 1, NULL);
> +		if (ret)
> +			return ret;
> +
> +		driver_data->pwm_enabled = val;

val is not range checked. Since pwm_enabled is declared as u8,
writing a multiple of 256 will cause it to be 0. This may result
in unexpected behavior.

> +
> +		/* Activating PWM sets speed to 0. Alternativ design decision
> +		 * could be to keep the current value. This would require proper
> +		 * setting of driver_data->curr_speed for example.
> +		 */
> +		if (val)
> +			for (i = 0; i < driver_data->fan_count; ++i) {
> +				ret = write_speed(dev, i, 0);
> +				if (ret)
> +					return ret;
> +			}
> +
> +		return 0;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static const struct hwmon_ops hwmops = {
> +	.is_visible = hwm_is_visible,
> +	.read = hwm_read,
> +	.read_string = hwm_read_string,
> +	.write = hwm_write,
> +};
> +
> +static struct hwmon_channel_info hwmcinfo_fan = {
> +	.type = hwmon_fan,
> +};
> +
> +static struct hwmon_channel_info hwmcinfo_pwm = {
> +	.type = hwmon_pwm,
> +};
> +
> +static struct hwmon_channel_info hwmcinfo_temp = {
> +	.type = hwmon_temp,
> +};
> +
> +static const struct hwmon_channel_info * const hwmcinfo[] = {
> +	&hwmcinfo_fan,
> +	&hwmcinfo_pwm,
> +	&hwmcinfo_temp,
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info hwminfo = {
> +	.ops = &hwmops,
> +	.info = hwmcinfo
> +};
> +
> +static void tuxi_periodic_hw_safeguard(struct work_struct *work)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data;
> +
> +	driver_data = container_of(work, struct tuxi_hwmon_driver_data_t,
> +				   work.work);
> +
> +	struct device *dev = driver_data->hwmdev;
> +	struct acpi_device *pdev = to_acpi_device(dev->parent);
> +	unsigned int i, j;
> +
> +	unsigned long long params[2];
> +	unsigned long long retval;
> +
> +	long temp, temp_low, temp_high;
> +	u8 temp_level, min_speed, curr_speed, want_speed;
> +
> +	for (i = 0; i < driver_data->fan_count; ++i) {
> +		params[0] = i;
> +		tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_GET_FAN_TEMPERATURE,
> +				 params, 1, &retval);

The return value from tuxi_tfan_method() is checked elsewhere. If there is
an error, retval may contain a random value. The resulting behavior may be
unexpected.

> +		temp = retval * 100 - 272000;
> +
> +		for (j = 0; temp_levels[j].temp; ++j) {
> +			temp_low = j == 0 ? -272000 : temp_levels[j-1].temp;
> +			temp_high = temp_levels[j].temp;
> +			if (driver_data->temp_level[i] > j)
> +				temp_high -= 2000; // hysteresis
> +
> +			if (temp >= temp_low && temp < temp_high)
> +				driver_data->temp_level[i] = j;
> +		}
> +		if (temp >= temp_high)
> +			driver_data->temp_level[i] = j;
> +
> +		temp_level = driver_data->temp_level[i];
> +		min_speed = temp_level == 0 ?
> +			0 : temp_levels[temp_level-1].min_speed;
> +		curr_speed = driver_data->curr_speed[i];
> +		want_speed = driver_data->want_speed[i];
> +
> +		if (want_speed < min_speed) {
> +			if (curr_speed < min_speed)
> +				write_speed(dev, i, min_speed);
> +		} else if (curr_speed != want_speed)
> +			write_speed(dev, i, want_speed);
> +	}
> +
> +	schedule_delayed_work(&driver_data->work, TUXI_SAFEGUARD_PERIOD);
> +}

This is not expected functionality of a hardware monitoring driver.
Hardware monmitoring drivers should not replicate userspace or
thermal subsystem functionality.

This would be unacceptable in drivers/hwmon/.

> +
> +int tuxi_hwmon_add_devices(struct acpi_device *pdev, struct device **hwmdev)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data;
> +	int ret;
> +
> +	unsigned long long params[2];
> +	unsigned long long retval;
> +
> +	u32 *hwmcinfo_fan_config, *hwmcinfo_pwm_config, *hwmcinfo_temp_config;
> +
> +	/* The first version of TUXI TFAN didn't have the Get Fan Temperature
> +	 * method which is integral to this driver. So probe for existence and
> +	 * abort otherwise.
> +	 *
> +	 * The Get Fan Speed method is also missing in that version, but was
> +	 * added in the same version so it doesn't have to be probe separately.
> +	 */
> +	params[0] = 0;
> +	ret = tuxi_tfan_method(pdev,
> +			       TUXI_TFAN_METHOD_GET_FAN_TEMPERATURE,
> +			       params, 1, &retval);
> +	if (ret)
> +		return ret;
> +
> +	driver_data = devm_kzalloc(&pdev->dev, sizeof(*driver_data),
> +				   GFP_KERNEL);
> +	if (!driver_data)
> +		return -ENOMEM;
> +
> +	/* Loading this module sets the fan mode to auto. Alternative design
> +	 * decision could be to keep the current value. This would require
> +	 * proper initialization of driver_data->curr_speed for example.
> +	 */
> +	params[0] = 0;
> +	ret = tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_SET_FAN_MODE, params, 1,
> +			       NULL);
> +	if (ret)
> +		return ret;
> +
> +	ret = tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_GET_FAN_COUNT, NULL, 0,
> +			       &retval);
> +	if (ret)
> +		return ret;
> +	driver_data->fan_count = retval;
> +
> +	driver_data->temp_level = devm_kcalloc(&pdev->dev,
> +					       driver_data->fan_count,
> +					       sizeof(*driver_data->temp_level),
> +					       GFP_KERNEL);
> +	if (driver_data->temp_level == NULL)
> +		return -ENOMEM;
> +	driver_data->curr_speed = devm_kcalloc(&pdev->dev,
> +					       driver_data->fan_count,
> +					       sizeof(*driver_data->curr_speed),
> +					       GFP_KERNEL);
> +	if (driver_data->curr_speed == NULL)
> +		return -ENOMEM;
> +	driver_data->want_speed = devm_kcalloc(&pdev->dev,
> +					       driver_data->fan_count,
> +					       sizeof(*driver_data->want_speed),
> +					       GFP_KERNEL);
> +	if (driver_data->want_speed == NULL)
> +		return -ENOMEM;
> +	driver_data->fan_types = devm_kcalloc(&pdev->dev,
> +					      driver_data->fan_count,
> +					      sizeof(*driver_data->fan_types),
> +					      GFP_KERNEL);
> +	if (driver_data->fan_types == NULL)
> +		return -ENOMEM;
> +
> +	hwmcinfo_fan_config = devm_kcalloc(&pdev->dev,
> +					   driver_data->fan_count + 1,
> +					   sizeof(*hwmcinfo_fan_config),
> +					   GFP_KERNEL);
> +	if (hwmcinfo_fan_config == NULL)
> +		return -ENOMEM;
> +	hwmcinfo_pwm_config = devm_kcalloc(&pdev->dev,
> +					   driver_data->fan_count + 1,
> +					   sizeof(*hwmcinfo_pwm_config),
> +					   GFP_KERNEL);
> +	if (hwmcinfo_pwm_config == NULL)
> +		return -ENOMEM;
> +	hwmcinfo_temp_config = devm_kcalloc(&pdev->dev,
> +					    driver_data->fan_count + 1,
> +					    sizeof(*hwmcinfo_temp_config),
> +					    GFP_KERNEL);
> +	if (hwmcinfo_temp_config == NULL)
> +		return -ENOMEM;
> +
> +	for (unsigned long long i = 0; i < driver_data->fan_count; ++i) {

driver_data->fan_count is declaered as u8. Using an unsigned long long to iterate
over it seems to be a bit unusual.

> +		hwmcinfo_fan_config[i] = HWMON_F_INPUT | HWMON_F_LABEL;
> +		hwmcinfo_pwm_config[i] = HWMON_PWM_INPUT | HWMON_PWM_ENABLE;
> +		hwmcinfo_temp_config[i] = HWMON_T_INPUT | HWMON_T_LABEL;
> +
> +		params[0] = i;
> +		ret = tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_GET_FAN_TYPE,
> +				       params, 1, &retval);
> +		if (ret)
> +			return ret;
> +		else if (retval >= ARRAY_SIZE(tuxi_fan_type_labels))
> +			return -EOPNOTSUPP;
> +		driver_data->fan_types[i] = tuxi_fan_type_labels[retval];
> +	}
> +	hwmcinfo_fan.config = hwmcinfo_fan_config;
> +	hwmcinfo_pwm.config = hwmcinfo_pwm_config;
> +	hwmcinfo_temp.config = hwmcinfo_temp_config;
> +

Personally I think this is way too complicated. It would make much more sense
to assume a reasonable maximum (say, 16) and use fixed size arrays to access
the data. The is_visible function can then simply return 0 for larger channel
values if the total number of fans is less than the ones configured in the
channel information.

Also, as already mentioned, there is no range check of fan_count. This will
cause some oddities if the system ever claims to have 256+ fans.

> +	*hwmdev = devm_hwmon_device_register_with_info(&pdev->dev,
> +						       "tuxedo_nbxx_acpi_tuxi",
> +						       driver_data, &hwminfo,
> +						       NULL);
> +	if (PTR_ERR_OR_ZERO(*hwmdev))
> +		return PTR_ERR_OR_ZERO(*hwmdev);
> +
Why not just return hwmdev ?

> +	driver_data->hwmdev = *hwmdev;
> +
> +	INIT_DELAYED_WORK(&driver_data->work, tuxi_periodic_hw_safeguard);
> +	schedule_delayed_work(&driver_data->work, TUXI_SAFEGUARD_PERIOD);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(tuxi_hwmon_add_devices);
> +
> +void tuxi_hwmon_remove_devices(struct device *hwmdev)
> +{
> +	struct tuxi_hwmon_driver_data_t *driver_data = dev_get_drvdata(hwmdev);
> +	struct acpi_device *pdev = to_acpi_device(hwmdev->parent);
> +
> +	unsigned long long params[2];
> +
> +	cancel_delayed_work_sync(&driver_data->work);
> +
> +	params[0] = 0;
> +	tuxi_tfan_method(pdev, TUXI_TFAN_METHOD_SET_FAN_MODE, params, 1, NULL);
> +}
> +EXPORT_SYMBOL(tuxi_hwmon_remove_devices);
> diff --git a/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.h b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.h
> new file mode 100644
> index 0000000000000..248730fab8574
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_hwmon.h
> @@ -0,0 +1,14 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2024-2025 Werner Sembach wse@...edocomputers.com
> + */
> +
> +#ifndef __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_HWMON_H__
> +#define __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_HWMON_H__
> +
> +#include <linux/acpi.h>
> +
> +int tuxi_hwmon_add_devices(struct acpi_device *pdev, struct device **hwmdev);
> +void tuxi_hwmon_remove_devices(struct device *hwmdev);
> +
> +#endif // __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_HWMON_H__
> diff --git a/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.c b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.c
> new file mode 100644
> index 0000000000000..5e8edb458aba2
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.c
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2024-2025 Werner Sembach wse@...edocomputers.com
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/module.h>
> +
> +#include "acpi_tuxi_hwmon.h"
> +
> +#include "acpi_tuxi_init.h"
> +
> +static const struct acpi_device_id acpi_device_ids[] = {
> +	{"TUXI0000", 0},
> +	{"", 0}
> +};
> +MODULE_DEVICE_TABLE(acpi, acpi_device_ids);
> +
> +static int add(struct acpi_device *device)
> +{
> +	struct tuxi_driver_data_t *driver_data;
> +	acpi_status status;
> +
> +	driver_data = devm_kzalloc(&device->dev, sizeof(*driver_data),
> +				   GFP_KERNEL);
> +	if (!driver_data)
> +		return -ENOMEM;
> +
> +	// Find subdevices
> +	status = acpi_get_handle(device->handle, "TFAN",
> +				 &driver_data->tfan_handle);
> +	if (ACPI_FAILURE(status))
> +		return_ACPI_STATUS(status);
> +
> +	dev_set_drvdata(&device->dev, driver_data);
> +
> +	return tuxi_hwmon_add_devices(device, &driver_data->hwmdev);
> +}
> +
> +static void remove(struct acpi_device *device)
> +{
> +	struct tuxi_driver_data_t *driver_data = dev_get_drvdata(&device->dev);
> +
> +	tuxi_hwmon_remove_devices(driver_data->hwmdev);
> +}
> +
> +static struct acpi_driver acpi_driver = {
> +	.name = "tuxedo_nbxx_acpi_tuxi",
> +	.ids = acpi_device_ids,
> +	.ops = {
> +		.add = add,
> +		.remove = remove,
> +	},
> +};
> +
> +module_acpi_driver(acpi_driver);
> +
> +MODULE_DESCRIPTION("TUXEDO TUXI");
> +MODULE_AUTHOR("Werner Sembach <wse@...edocomputers.com>");
> +MODULE_LICENSE("GPL");
> diff --git a/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.h b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.h
> new file mode 100644
> index 0000000000000..33388332a2328
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_init.h
> @@ -0,0 +1,16 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2024-2025 Werner Sembach wse@...edocomputers.com
> + */
> +
> +#ifndef __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_INIT_H__
> +#define __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_INIT_H__
> +
> +#include <linux/acpi.h>
> +
> +struct tuxi_driver_data_t {
> +	acpi_handle tfan_handle;
> +	struct device *hwmdev;
> +};
> +
> +#endif // __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_INIT_H__
> diff --git a/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.c b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.c
> new file mode 100644
> index 0000000000000..292b739a161e7
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.c
> @@ -0,0 +1,58 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2024-2025 Werner Sembach wse@...edocomputers.com
> + */
> +
> +#include <linux/acpi.h>
> +
> +#include "acpi_tuxi_init.h"
> +
> +#include "acpi_tuxi_util.h"
> +
> +static int __acpi_eval_intarray_in_int_out(acpi_handle handle,
> +					   acpi_string pathname,
> +					   unsigned long long *params,
> +					   u32 pcount,
> +					   unsigned long long *retval)
> +{
> +	struct acpi_object_list arguments;
> +	unsigned long long data;
> +	acpi_status status;
> +
> +	if (pcount > 0) {
> +		pr_debug("Params:\n");
> +
> +		arguments.count = pcount;
> +		arguments.pointer = kcalloc(pcount, sizeof(*arguments.pointer),
> +					    GFP_KERNEL);
> +		for (int i = 0; i < pcount; ++i) {
> +			pr_debug("%llu\n", params[i]);
> +
> +			arguments.pointer[i].type = ACPI_TYPE_INTEGER;
> +			arguments.pointer[i].integer.value = params[i];
> +		}
> +		status = acpi_evaluate_integer(handle, pathname, &arguments,
> +					       &data);
> +		kfree(arguments.pointer);
> +	} else {
> +		status = acpi_evaluate_integer(handle, pathname, NULL, &data);
> +	}
> +	if (ACPI_FAILURE(status))
> +		return_ACPI_STATUS(status);
> +
> +	if (retval)
> +		*retval = data;
> +
> +	return 0;
> +}
> +
> +int tuxi_tfan_method(struct acpi_device *device, acpi_string method,
> +		     unsigned long long *params, u32 pcount,
> +		     unsigned long long *retval)
> +{
> +	struct tuxi_driver_data_t *driver_data = dev_get_drvdata(&device->dev);
> +
> +	return __acpi_eval_intarray_in_int_out(driver_data->tfan_handle, method,
> +					       params, pcount, retval);
> +}
> +EXPORT_SYMBOL(tuxi_tfan_method);
> diff --git a/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.h b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.h
> new file mode 100644
> index 0000000000000..670fe02249d06
> --- /dev/null
> +++ b/drivers/platform/x86/tuxedo/nbxx/acpi_tuxi_util.h
> @@ -0,0 +1,84 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Copyright (C) 2024-2025 Werner Sembach wse@...edocomputers.com
> + */
> +
> +#ifndef __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_UTIL_H__
> +#define __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_UTIL_H__
> +
> +#include <linux/acpi.h>
> +
> +/*
> + * Set fan speed target
> + *
> + * Set a specific fan speed (needs manual mode)
> + *
> + * Arg0: Fan index
> + * Arg1: Fan speed as a fraction of maximum speed (0-255)
> + */
> +#define TUXI_TFAN_METHOD_SET_FAN_SPEED		"SSPD"
> +
> +/*
> + * Get fan speed target
> + *
> + * Arg0: Fan index
> + * Returns: Current fan speed target a fraction of maximum speed (0-255)
> + */
> +#define TUXI_TFAN_METHOD_GET_FAN_SPEED		"GSPD"
> +
> +/*
> + * Get fans count
> + *
> + * Returns: Number of individually controllable fans
> + */
> +#define TUXI_TFAN_METHOD_GET_FAN_COUNT		"GCNT"
> +
> +/*
> + * Set fans mode
> + *
> + * Arg0: 0 = auto, 1 = manual
> + */
> +#define TUXI_TFAN_METHOD_SET_FAN_MODE		"SMOD"
> +
> +/*
> + * Get fans mode
> + *
> + * Returns: 0 = auto, 1 = manual
> + */
> +#define TUXI_TFAN_METHOD_GET_FAN_MODE		"GMOD"
> +
> +/*
> + * Get fan type/what the fan is pointed at
> + *
> + * Arg0: Fan index
> + * Returns: 0 = general, 1 = CPU, 2 = GPU
> + */
> +#define TUXI_TFAN_METHOD_GET_FAN_TYPE		"GTYP"
> +
> +static const char * const tuxi_fan_type_labels[] = {
> +	"general",
> +	"cpu",
> +	"gpu"
> +};
> +
> +/*
> + * Get fan temperature/temperature of what the fan is pointed at
> + *
> + * Arg0: Fan index
> + * Returns: Temperature sensor value in 10ths of degrees kelvin
> + */
> +#define TUXI_TFAN_METHOD_GET_FAN_TEMPERATURE	"GTMP"
> +
> +/*
> + * Get actual fan speed in RPM
> + *
> + * Arg0: Fan index
> + * Returns: Speed sensor value in revolutions per minute
> + */
> +#define TUXI_TFAN_METHOD_GET_FAN_RPM		"GRPM"
> +
> +int tuxi_tfan_method(struct acpi_device *device, acpi_string method,
> +		     unsigned long long *params, u32 pcount,
> +		     unsigned long long *retval);
> +
> +#endif // __PLATFORM_X86_TUXEDO_NBXX_ACPI_TUXI_UTIL_H__

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