Re: [PATCH v8 11/14] platform/x86: oxpec: Adhere to sysfs-class-hwmon and enable pwm on 2

[Ilpo Järvinen]

On Sat, 22 Mar 2025, Antheas Kapenekakis wrote:

> Currently, the driver does not adhere to the sysfs-class-hwmon
> specification: 0 is used for auto fan control and 1 is used for manual
> control. However, it is expected that 0 sets the fan to full speed,
> 1 sets the fan to manual, and then 2 is used for automatic control.
> 
> Therefore, change the sysfs API to reflect this and enable pwm on 2.
> 
> As we are breaking the ABI for this driver, rename oxpec to oxp_ec,
> reflecting the naming convention used by other drivers, to allow for
> a smooth migration in current userspace programs.

So there's no gracious deprecation of the previous interface? It doesn't 
sound "smooth" by any means from userspace perspective.

> Closes: https://lore.kernel.org/linux-hwmon/20241027174836.8588-1-derekjohn.clark@xxxxxxxxx/
> Reviewed-by: Derek J. Clark <derekjohn.clark@xxxxxxxxx>
> Reviewed-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
> Signed-off-by: Antheas Kapenekakis <lkml@xxxxxxxxxxx>
> ---
>  drivers/platform/x86/oxpec.c | 37 ++++++++++++++++++++++++++++++++----
>  1 file changed, 33 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/platform/x86/oxpec.c b/drivers/platform/x86/oxpec.c
> index 5b84647569931..3bf2c597e9b00 100644
> --- a/drivers/platform/x86/oxpec.c
> +++ b/drivers/platform/x86/oxpec.c
> @@ -731,7 +731,27 @@ static int oxp_platform_read(struct device *dev, enum hwmon_sensor_types type,
>  		case hwmon_pwm_input:
>  			return oxp_pwm_input_read(val);
>  		case hwmon_pwm_enable:
> -			return oxp_pwm_read(val);
> +			ret = oxp_pwm_read(val);
> +			if (ret)
> +				return ret;
> +
> +			/* Check for auto and return 2 */
> +			if (!*val) {
> +				*val = 2;
> +				return 0;
> +			}
> +
> +			/* Return 0 if at full fan speed, 1 otherwise */
> +			ret = oxp_pwm_fan_speed(val);
> +			if (ret)
> +				return ret;
> +
> +			if (*val == 255)
> +				*val = 0;
> +			else
> +				*val = 1;

Why all these literals? These should be named properly with defines are 
there some defines/enums for some of them already if this hwmon ABI?

> +
> +			return 0;
>  		default:
>  			break;
>  		}
> @@ -745,15 +765,24 @@ static int oxp_platform_read(struct device *dev, enum hwmon_sensor_types type,
>  static int oxp_platform_write(struct device *dev, enum hwmon_sensor_types type,
>  			      u32 attr, int channel, long val)
>  {
> +	int ret;
> +
>  	switch (type) {
>  	case hwmon_pwm:
>  		switch (attr) {
>  		case hwmon_pwm_enable:
>  			if (val == 1)
>  				return oxp_pwm_enable();
> -			else if (val == 0)
> +			else if (val == 2)
>  				return oxp_pwm_disable();
> -			return -EINVAL;
> +			else if (val != 0)

Literals here too should be changed.

> +				return -EINVAL;
> +
> +			/* Enable PWM and set to max speed */
> +			ret = oxp_pwm_enable();
> +			if (ret)
> +				return ret;
> +			return oxp_pwm_input_write(255);
>  		case hwmon_pwm_input:
>  			return oxp_pwm_input_write(val);
>  		default:
> @@ -818,7 +847,7 @@ static int oxp_platform_probe(struct platform_device *pdev)
>  	struct device *dev = &pdev->dev;
>  	struct device *hwdev;
>  
> -	hwdev = devm_hwmon_device_register_with_info(dev, "oxpec", NULL,
> +	hwdev = devm_hwmon_device_register_with_info(dev, "oxp_ec", NULL,
>  						     &oxp_ec_chip_info, NULL);
>  
>  	return PTR_ERR_OR_ZERO(hwdev);
> 

-- 
 i.