Re: [PATCH v8] ACPI: fan: Add hwmon support

[Rafael J. Wysocki]

On Fri, May 10, 2024 at 10:13 PM Armin Wolf <W_Armin@xxxxxx> wrote:
>
> Currently, the driver does only support 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".
>
> Reviewed-by: Andy Shevchenko <andy@xxxxxxxxxx>
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
> Tested witha custom ACPI SSDT, available here:
> https://github.com/Wer-Wolf/acpi-fan-ssdt
>
> Changes since v7:
> - add Reviewed-by tag
> - spelling fixes
> - add missing types.h include
>
> Changes since v6:
> - add "hwmon" to the names of functions and variables
> related to hwmon
> - replace -ENODATA with -EIO/-ENODEV
>
> Changes since v5:
> - fix coding style issues
> - replace double break with return
> - add missing includes
>
> Changes since v4:
> - fix spelling issues
> - check power values for overflow condition too
>
> Changes since v3:
> - drop fault attrs
> - rework initialization
>
> 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
> ---
>  drivers/acpi/Makefile    |   1 +
>  drivers/acpi/fan.h       |   9 +++
>  drivers/acpi/fan_core.c  |   4 +
>  drivers/acpi/fan_hwmon.c | 170 +++++++++++++++++++++++++++++++++++++++
>  4 files changed, 184 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..bd0d31a398fa
> --- /dev/null
> +++ b/drivers/acpi/fan_hwmon.c
> @@ -0,0 +1,170 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * hwmon interface for the ACPI Fan driver.
> + *
> + * Copyright (C) 2024 Armin Wolf <W_Armin@xxxxxx>
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/device.h>
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/limits.h>
> +#include <linux/types.h>
> +#include <linux/units.h>
> +
> +#include "fan.h"
> +
> +/* Returned when the ACPI fan does not support speed reporting */
> +#define FAN_SPEED_UNAVAILABLE  U32_MAX
> +#define FAN_POWER_UNAVAILABLE  U32_MAX
> +
> +static struct acpi_fan_fps *acpi_fan_get_current_fps(struct acpi_fan *fan, u64 control)
> +{
> +       unsigned 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_hwmon_is_visible(const void *drvdata, enum hwmon_sensor_types type,
> +                                        u32 attr, int channel)
> +{
> +       const struct acpi_fan *fan = drvdata;
> +       unsigned int i;

AFAICS, the code below can be rewritten as follows:

if (fan->fif.fine_grain_ctrl)
         return 0;

switch (type) {
case hwmon_fan:
        if (attr == hwmon_fan_input || attr == hwmon_fan_target)
               return 0444;

        return 0;

case hwmon_power:
        if (attr == hwmon_power_input) {
               for (i = 0; i < fan->fps_count; i++) {
                       if (fan->fps[i].power != FAN_POWER_UNAVAILABLE)
                               return 0444;
               }
        }

        fallthrough;
default:
       return 0;
}

without changing functionality, which is both less duplication and
fewer lines of code.

> +
> +       switch (type) {
> +       case hwmon_fan:
> +               switch (attr) {
> +               case hwmon_fan_input:
> +                       return 0444;
> +               case hwmon_fan_target:
> +                       /*
> +                        * When in fine grain control mode, not every fan control value
> +                        * has an associated fan performance state.
> +                        */
> +                       if (fan->fif.fine_grain_ctrl)
> +                               return 0;
> +
> +                       return 0444;
> +               default:
> +                       return 0;
> +               }
> +       case hwmon_power:
> +               switch (attr) {
> +               case hwmon_power_input:
> +                       /*
> +                        * When in fine grain control mode, not every fan control value
> +                        * has an associated fan performance state.
> +                        */
> +                       if (fan->fif.fine_grain_ctrl)
> +                               return 0;
> +
> +                       /*
> +                        * When all fan performance states contain no valid power data,
> +                        * when the associated attribute should not be created.
> +                        */
> +                       for (i = 0; i < fan->fps_count; i++) {
> +                               if (fan->fps[i].power != FAN_POWER_UNAVAILABLE)
> +                                       return 0444;
> +                       }
> +
> +                       return 0;
> +               default:
> +                       return 0;
> +               }
> +       default:
> +               return 0;
> +       }
> +}
> +
> +static int acpi_fan_hwmon_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
> +                              int channel, long *val)
> +{
> +       struct acpi_device *adev = to_acpi_device(dev->parent);
> +       struct acpi_fan *fan = dev_get_drvdata(dev);
> +       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 -ENODEV;
> +
> +                       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 -EIO;
> +
> +                       if (fps->speed > LONG_MAX)
> +                               return -EOVERFLOW;
> +
> +                       *val = fps->speed;
> +                       return 0;
> +               default:
> +                       return -EOPNOTSUPP;
> +               }
> +       case hwmon_power:
> +               switch (attr) {
> +               case hwmon_power_input:
> +                       fps = acpi_fan_get_current_fps(fan, fst.control);
> +                       if (!fps)
> +                               return -EIO;
> +
> +                       if (fps->power == FAN_POWER_UNAVAILABLE)
> +                               return -ENODEV;
> +
> +                       if (fps->power > LONG_MAX / MICROWATT_PER_MILLIWATT)
> +                               return -EOVERFLOW;
> +
> +                       *val = fps->power * MICROWATT_PER_MILLIWATT;
> +                       return 0;
> +               default:
> +                       return -EOPNOTSUPP;
> +               }
> +       default:
> +               return -EOPNOTSUPP;
> +       }
> +}
> +
> +static const struct hwmon_ops acpi_fan_hwmon_ops = {
> +       .is_visible = acpi_fan_hwmon_is_visible,
> +       .read = acpi_fan_hwmon_read,
> +};
> +
> +static const struct hwmon_channel_info * const acpi_fan_hwmon_info[] = {
> +       HWMON_CHANNEL_INFO(fan, HWMON_F_INPUT | HWMON_F_TARGET),
> +       HWMON_CHANNEL_INFO(power, HWMON_P_INPUT),
> +       NULL
> +};
> +
> +static const struct hwmon_chip_info acpi_fan_hwmon_chip_info = {
> +       .ops = &acpi_fan_hwmon_ops,
> +       .info = acpi_fan_hwmon_info,
> +};
> +
> +int devm_acpi_fan_create_hwmon(struct acpi_device *device)
> +{
> +       struct acpi_fan *fan = acpi_driver_data(device);
> +       struct device *hdev;
> +
> +       hdev = devm_hwmon_device_register_with_info(&device->dev, "acpi_fan", fan,
> +                                                   &acpi_fan_hwmon_chip_info, NULL);
> +       return PTR_ERR_OR_ZERO(hdev);
> +}
> --
> 2.39.2
>
>