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

[Armin Wolf]

Am 08.04.24 um 17:48 schrieb 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?

Hi,

i think so, since the value of the attribute (with the meaning of "is the rpm value ok?") is being
correctly stored in val. If acpi_fan_get_fst() fails, we already return a negative error code.

Thanks,
Armin Wolf

> > +		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.