Re: [PATCH 6/8] hwmon: (tmp421) support specifying n-factor via DT

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

On 9/7/21 6:45 AM, Krzysztof Adamski wrote:
> Previous patches added a way to specify some channel specific parameters
> in DT and n-factor is definitely one of them. This calibration mechanism
> is board specific as its value depends on the diodes/transistors being
> connected to the sensor and thus the DT seems like a right fit for that
> information. It is very similar to the value of shunt resistor that some
> drivers allows specifying in DT.
> 
> This patch adds a possibility to set n-factor for each channel via
> "n-factor" DT property in each channel subnode.
> 
> Signed-off-by: Krzysztof Adamski <krzysztof.adamski@nokia.com>
> ---
>   drivers/hwmon/tmp421.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 
> diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
> index a41d7935acb9..90c6b094785e 100644
> --- a/drivers/hwmon/tmp421.c
> +++ b/drivers/hwmon/tmp421.c
> @@ -34,6 +34,7 @@ enum chips { tmp421, tmp422, tmp423, tmp441, tmp442 };
>   #define TMP421_STATUS_REG			0x08
>   #define TMP421_CONFIG_REG_1			0x09
>   #define TMP421_CONVERSION_RATE_REG		0x0B
> +#define TMP421_N_FACTOR_REG_1			0x21
>   #define TMP421_MANUFACTURER_ID_REG		0xFE
>   #define TMP421_DEVICE_ID_REG			0xFF
>   
> @@ -302,6 +303,7 @@ void tmp421_probe_child_from_dt(struct i2c_client *client,
>   {
>   	struct device *dev = &client->dev;
>   	u32 i;
> +	s32 val;
>   	int err;
>   
>   	err = of_property_read_u32(child, "reg", &i);
> @@ -321,6 +323,21 @@ void tmp421_probe_child_from_dt(struct i2c_client *client,
>   		data->channel[i].disabled = true;
>   		return;
>   	}
> +
> +	if (i == 0)
> +		return; /* input 0 is internal channel */
> +
> +	err = of_property_read_s32(child, "n-factor", &val);
> +	if (!err) {
> +		if (val > 127 || val < -128)
> +			dev_err(dev, "n-factor for channel %d invalid (%d)\n",
> +				i, val);

This should report an error to the caller.

Guenter

> +		else
> +			i2c_smbus_write_byte_data(client,
> +						  TMP421_N_FACTOR_REG_1 + i - 1,
> +						  val);
> +	}
> +
>   }
>   
>   void tmp421_probe_from_dt(struct i2c_client *client, struct tmp421_data *data)
>