Re: [PATCH 5/8] hwmon: (tmp421) support disabling channels from DT

[Guenter Roeck <linux@roeck-us.net>]

On 9/7/21 6:43 AM, Krzysztof Adamski wrote:
> The previous patch introduced per channel subnodes in DT that let us
> specify some channel specific properties. This built a ground for easily
> disabling individual channels of the sensor that may not be connected to
> any external diode and thus are not returning any meaningful data.
> 
> This patch adds support for parsing the "status" property of channels DT
> subnodes and makes sure the -ENODATA is returned when disabled channels
> value is read.
> 

If channels can be disabled via DT, the respective sysfs attribute (tempX_enable)
should also be supported.

> Signed-off-by: Krzysztof Adamski <krzysztof.adamski@nokia.com>
> ---
>   drivers/hwmon/tmp421.c | 17 ++++++++++++-----
>   1 file changed, 12 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
> index a1dba1d405ee..a41d7935acb9 100644
> --- a/drivers/hwmon/tmp421.c
> +++ b/drivers/hwmon/tmp421.c
> @@ -89,6 +89,7 @@ MODULE_DEVICE_TABLE(of, tmp421_of_match);
>   
>   struct tmp421_channel {
>   	const char *label;
> +	bool disabled;
>   	s16 temp;
>   };
>   
> @@ -125,9 +126,8 @@ static int temp_from_u16(u16 reg)
>   	return (temp * 1000 + 128) / 256;
>   }
>   
> -static struct tmp421_data *tmp421_update_device(struct device *dev)
> +static void tmp421_update_device(struct tmp421_data *data)
>   {
> -	struct tmp421_data *data = dev_get_drvdata(dev);
>   	struct i2c_client *client = data->client;
>   	int i;
>   
> @@ -149,14 +149,17 @@ static struct tmp421_data *tmp421_update_device(struct device *dev)
>   	}
>   
>   	mutex_unlock(&data->update_lock);
> -
> -	return data;
>   }
>   
>   static int tmp421_read(struct device *dev, enum hwmon_sensor_types type,
>   		       u32 attr, int channel, long *val)
>   {
> -	struct tmp421_data *tmp421 = tmp421_update_device(dev);
> +	struct tmp421_data *tmp421 = dev_get_drvdata(dev);
> +
> +	if (tmp421->channel[channel].disabled)
> +		return -ENODATA;
> +
> +	tmp421_update_device(tmp421);
>   
>   	switch (attr) {
>   	case hwmon_temp_input:
> @@ -314,6 +317,10 @@ void tmp421_probe_child_from_dt(struct i2c_client *client,
>   	if (data->channel[i].label)
>   		data->temp_config[i] |= HWMON_T_LABEL;
>   
> +	if (!of_device_is_available(child)) {
> +		data->channel[i].disabled = true;
> +		return;
> +	}
>   }
>   
>   void tmp421_probe_from_dt(struct i2c_client *client, struct tmp421_data *data)
>