Re: [PATCH] ACPI: fan: Add hwmon support

[Ilpo Järvinen]

On Mon, 8 Apr 2024, Armin Wolf wrote:

> Currently, the driver does only supports a custom sysfs
> interface 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".
> 
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
>  drivers/acpi/Makefile    |  1 +
>  drivers/acpi/fan.h       |  2 ++
>  drivers/acpi/fan_core.c  |  7 ++++
>  drivers/acpi/fan_hwmon.c | 78 ++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 88 insertions(+)
>  create mode 100644 drivers/acpi/fan_hwmon.c
> 
> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
> index d69d5444acdb..9a2e03acc1be 100644
> --- a/drivers/acpi/Makefile
> +++ b/drivers/acpi/Makefile
> @@ -83,6 +83,7 @@ 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-objs			+= 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 e7b4b4e4a55e..45c2637566da 100644
> --- a/drivers/acpi/fan.h
> +++ b/drivers/acpi/fan.h
> @@ -56,4 +56,6 @@ 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);
> +
> +int devm_acpi_fan_create_hwmon(struct acpi_device *device);
>  #endif
> diff --git a/drivers/acpi/fan_core.c b/drivers/acpi/fan_core.c
> index ff72e4ef8738..6bbdbb914e95 100644
> --- a/drivers/acpi/fan_core.c
> +++ b/drivers/acpi/fan_core.c
> @@ -7,6 +7,7 @@
>   *  Copyright (C) 2022 Intel Corporation. All rights reserved.
>   */
> 
> +#include <linux/kconfig.h>
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> @@ -336,6 +337,12 @@ static int acpi_fan_probe(struct platform_device *pdev)
>  		if (result)
>  			return result;
> 
> +		if (IS_REACHABLE(CONFIG_HWMON)) {
> +			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..4f2bec8664f4
> --- /dev/null
> +++ b/drivers/acpi/fan_hwmon.c
> @@ -0,0 +1,78 @@
> +// 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 "fan.h"
> +
> +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_fst fst;
> +	int ret;
> +
> +	switch (type) {
> +	case hwmon_fan:
> +		ret = acpi_fan_get_fst(adev, &fst);
> +		if (ret < 0)
> +			return ret;
> +
> +		switch (attr) {
> +		case hwmon_fan_input:
> +			if (fst.speed > LONG_MAX)
> +				return -EOVERFLOW;
> +
> +			*val = fst.speed;
> +			return 0;
> +		case hwmon_fan_fault:
> +			*val = (fst.speed == U32_MAX);
> +			return 0;

Is it okay to return 0 in this case?

> +		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_FAULT),

One line.

-- 
 i.


> +	NULL
> +};
> +
> +static const struct hwmon_chip_info acpi_fan_chip_info = {
> +	.ops = &acpi_fan_ops,
> +	.info = acpi_fan_info,
> +};
> +
> +int devm_acpi_fan_create_hwmon(struct acpi_device *device)
> +{
> +	struct device *hdev;
> +
> +	hdev = devm_hwmon_device_register_with_info(&device->dev, "acpi_fan", device,
> +						    &acpi_fan_chip_info, NULL);
> +
> +	return PTR_ERR_OR_ZERO(hdev);
> +}
> --
> 2.39.2
> 
>