Re: [PATCH v3 2/2] ACPI: fan: Add hwmon support

[Guenter Roeck]

On Fri, Apr 12, 2024 at 06:08:57PM +0200, Armin Wolf wrote:
> Currently, the driver does only support a custom sysfs
> to allow userspace to read the fan speed.
> Add support for the standard hwmon interface so users
> can read the fan speed with standard tools like "sensors".
> 
> Compile-tested only.
> 
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
> Changes since v2:
> - add support for fanX_target and power attrs
> 
> Changes since v1:
> - fix undefined reference error
> - fix fan speed validation
> - coding style fixes
> - clarify that the changes are compile-tested only
> - add hwmon maintainers to cc list
> 
> The changes will be tested by Mikael Lund Jepsen from Danelec and
> should be merged only after those tests.
> ---
>  drivers/acpi/Makefile    |   1 +
>  drivers/acpi/fan.h       |   9 +++
>  drivers/acpi/fan_core.c  |   4 ++
>  drivers/acpi/fan_hwmon.c | 148 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 162 insertions(+)
>  create mode 100644 drivers/acpi/fan_hwmon.c
> 
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index 39ea5cfa8326..61ca4afe83dc 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -77,6 +77,7 @@ obj-$(CONFIG_ACPI_TINY_POWER_BUTTON)	+= tiny-power-button.o
>  obj-$(CONFIG_ACPI_FAN)		+= fan.o
>  fan-objs			:= fan_core.o
>  fan-objs			+= fan_attr.o
> +fan-$(CONFIG_HWMON)		+= fan_hwmon.o
> 
>  obj-$(CONFIG_ACPI_VIDEO)	+= video.o
>  obj-$(CONFIG_ACPI_TAD)		+= acpi_tad.o
> diff --git a/drivers/acpi/fan.h b/drivers/acpi/fan.h
> index f89d19c922dc..db25a3898af7 100644
> --- a/drivers/acpi/fan.h
> +++ b/drivers/acpi/fan.h
> @@ -10,6 +10,8 @@
>  #ifndef _ACPI_FAN_H_
>  #define _ACPI_FAN_H_
> 
> +#include <linux/kconfig.h>
> +
>  #define ACPI_FAN_DEVICE_IDS	\
>  	{"INT3404", }, /* Fan */ \
>  	{"INTC1044", }, /* Fan for Tiger Lake generation */ \
> @@ -57,4 +59,11 @@ struct acpi_fan {
>  int acpi_fan_get_fst(struct acpi_device *device, struct acpi_fan_fst *fst);
>  int acpi_fan_create_attributes(struct acpi_device *device);
>  void acpi_fan_delete_attributes(struct acpi_device *device);
> +
> +#if IS_REACHABLE(CONFIG_HWMON)
> +int devm_acpi_fan_create_hwmon(struct acpi_device *device);
> +#else
> +static inline int devm_acpi_fan_create_hwmon(struct acpi_device *device) { return 0; };
> +#endif
> +
>  #endif
> diff --git a/drivers/acpi/fan_core.c b/drivers/acpi/fan_core.c
> index ff72e4ef8738..7cea4495f19b 100644
> --- a/drivers/acpi/fan_core.c
> +++ b/drivers/acpi/fan_core.c
> @@ -336,6 +336,10 @@ static int acpi_fan_probe(struct platform_device *pdev)
>  		if (result)
>  			return result;
> 
> +		result = devm_acpi_fan_create_hwmon(device);
> +		if (result)
> +			return result;
> +
>  		result = acpi_fan_create_attributes(device);
>  		if (result)
>  			return result;
> diff --git a/drivers/acpi/fan_hwmon.c b/drivers/acpi/fan_hwmon.c
> new file mode 100644
> index 000000000000..57216ba872db
> --- /dev/null
> +++ b/drivers/acpi/fan_hwmon.c
> @@ -0,0 +1,148 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * fan_hwmon.c - hwmon interface for the ACPI Fan driver
> + *
> + * Copyright (C) 2024 Armin Wolf <W_Armin@xxxxxx>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/hwmon.h>
> +#include <linux/limits.h>
> +#include <linux/units.h>
> +
> +#include "fan.h"
> +
> +/* Returned when the ACPI fan does not support speed reporting */
> +#define FAN_SPEED_UNAVAILABLE	0xffffffff
> +#define FAN_POWER_UNAVAILABLE	0xffffffff
> +
> +static struct acpi_fan_fps *acpi_fan_get_current_fps(struct acpi_fan *fan, u64 control)
> +{
> +	int i;
> +
> +	for (i = 0; i < fan->fps_count; i++) {
> +		if (fan->fps[i].control == control)
> +			return &fan->fps[i];
> +	}
> +
> +	return NULL;
> +}
> +
> +static umode_t acpi_fan_is_visible(const void *drvdata, enum hwmon_sensor_types type, u32 attr,
> +				   int channel)
> +{
> +	return 0444;
> +}
> +
> +static int acpi_fan_read(struct device *dev, enum hwmon_sensor_types type, u32 attr, int channel,
> +			 long *val)
> +{
> +	struct acpi_device *adev = dev_get_drvdata(dev);
> +	struct acpi_fan *fan = acpi_driver_data(adev);
> +	struct acpi_fan_fps *fps;
> +	struct acpi_fan_fst fst;
> +	int ret;
> +
> +	ret = acpi_fan_get_fst(adev, &fst);
> +	if (ret < 0)
> +		return ret;
> +
> +	switch (type) {
> +	case hwmon_fan:
> +		switch (attr) {
> +		case hwmon_fan_input:
> +			if (fst.speed == FAN_SPEED_UNAVAILABLE)
> +				return -ENODATA;
> +
> +			if (fst.speed > LONG_MAX)
> +				return -EOVERFLOW;
> +
> +			*val = fst.speed;
> +			return 0;
> +		case hwmon_fan_target:
> +			fps = acpi_fan_get_current_fps(fan, fst.control);
> +			if (!fps)
> +				return -ENODATA;
> +
> +			*val = fps->speed;
> +			return 0;
> +		case hwmon_fan_fault:
> +			*val = (fst.speed == FAN_SPEED_UNAVAILABLE);

Is it documented that this is indeed a fault (broken fan) ?

> +			return 0;
> +		default:
> +			break;
> +		}
> +		break;
> +	case hwmon_power:
> +		fps = acpi_fan_get_current_fps(fan, fst.control);
> +		if (!fps)
> +			return -ENODATA;
> +
> +		switch (attr) {
> +		case hwmon_power_input:
> +			if (fps->power == FAN_POWER_UNAVAILABLE)
> +				return -ENODATA;
> +
> +			if (fps->power > LONG_MAX / MICROWATT_PER_MILLIWATT)
> +				return -EOVERFLOW;
> +
> +			*val = fps->power * MICROWATT_PER_MILLIWATT;
> +			return 0;
> +		case hwmon_power_fault:
> +			*val = (fps->power == FAN_POWER_UNAVAILABLE);

Is it documented that this is indeed a power supply failure ?
What if the value is simply not reported ? "UNAVAILABLE" is not
commonly associated with a "fault".

Guenter

> +			return 0;
> +		default:
> +			break;
> +		}
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return -EOPNOTSUPP;
> +}
> +
> +static const struct hwmon_ops acpi_fan_ops = {
> +	.is_visible = acpi_fan_is_visible,
> +	.read = acpi_fan_read,
> +};
> +
> +static const struct hwmon_channel_info * const acpi_fan_info[] = {
> +	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_TARGET |  HWMON_F_FAULT),
> +	HWMON_CHANNEL_INFO(power, HWMON_P_INPUT | HWMON_P_FAULT),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info acpi_fan_chip_info = {
> +	.ops = &acpi_fan_ops,
> +	.info = acpi_fan_info,
> +};
> +
> +static const struct hwmon_channel_info * const acpi_fan_fine_grain_info[] = {
> +	HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_FAULT),
> +	NULL
> +};
> +
> +static const struct hwmon_chip_info acpi_fan_fine_grain_chip_info = {
> +	.ops = &acpi_fan_ops,
> +	.info = acpi_fan_fine_grain_info,
> +};
> +
> +int devm_acpi_fan_create_hwmon(struct acpi_device *device)
> +{
> +	struct acpi_fan *fan = acpi_driver_data(device);
> +	const struct hwmon_chip_info *info;
> +	struct device *hdev;
> +
> +	/* When in fine grain control mode, not every fan control value
> +	 * has an associated fan performance state.
> +	 */
> +	if (fan->fif.fine_grain_ctrl)
> +		info = &acpi_fan_fine_grain_chip_info;
> +	else
> +		info = &acpi_fan_chip_info;
> +
> +	hdev = devm_hwmon_device_register_with_info(&device->dev, "acpi_fan", device, info, NULL);
> +
> +	return PTR_ERR_OR_ZERO(hdev);
> +}
> --
> 2.39.2
>