linux-kernel - Re: [PATCH v2 4/5] iio: mcp9600: Add support for dtbinding of thermocouple-type

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Message-ID: <CAHp75Vd=gNzqWLSQcyc3MjHY7TAGizQ5TPS+99UCrnKDgUPTig@mail.gmail.com>
Date: Wed, 13 Aug 2025 18:49:30 +0200
From: Andy Shevchenko <andy.shevchenko@...il.com>
To: Ben Collins <bcollins@...ter.com>
Cc: Jonathan Cameron <jic23@...nel.org>, David Lechner <dlechner@...libre.com>, 
	Nuno Sá <nuno.sa@...log.com>, 
	Andy Shevchenko <andy@...nel.org>, linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/5] iio: mcp9600: Add support for dtbinding of thermocouple-type

On Wed, Aug 13, 2025 at 5:17 PM Ben Collins <bcollins@...ter.com> wrote:
>
> Adds dtbinding check for thermocouple-type and sets sensor config

Adds --> Add

Btw, I do not see dtbinding check here. There is some validation code
or so. Please, make sure your commit message is close enough to what's
going on.

> to match. Add iio info attribute to show state as well.

...

> +#define MCP9600_SENSOR_CFG             0x5

0x05

> +#define MCP9600_SENSOR_TYPE_MASK       GENMASK(6, 4)

...

> +/* Map dtbinding enums to mcp9600 sensor type */

I am not sure how this comment is useful, but since it does some
magic, this magic should be explained: why do you need to map these?

> +static const unsigned int mcp9600_type_map[] = {
> +       [THERMOCOUPLE_TYPE_K] = 0,
> +       [THERMOCOUPLE_TYPE_J] = 1,
> +       [THERMOCOUPLE_TYPE_T] = 2,
> +       [THERMOCOUPLE_TYPE_N] = 3,
> +       [THERMOCOUPLE_TYPE_S] = 4,
> +       [THERMOCOUPLE_TYPE_E] = 5,
> +       [THERMOCOUPLE_TYPE_B] = 6,
> +       [THERMOCOUPLE_TYPE_R] = 7,
> +};

Are they not 1:1?

...

> +/* Map mcp9600 sensor type to char */
> +static const int mcp9600_tc_types[] = {
> +       'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'

Please, leave the trailing comma, also why is this not indexed as the above?

> +};

...

>                         .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |         \
> -                                             BIT(IIO_CHAN_INFO_SCALE),        \
> +                                             BIT(IIO_CHAN_INFO_SCALE) |       \
> +                                             BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE), \

Make it only one line +, and *not* remove one / add two.

...

>   static int mcp9600_read_raw(struct iio_dev *indio_dev,

>                 *val = 62;
>                 *val2 = 500000;
>                 return IIO_VAL_INT_PLUS_MICRO;
> +       case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
> +               *val = mcp9600_tc_types[data->thermocouple_type];
> +               return IIO_VAL_CHAR;

> +

Stray blank line (I don't see the above is using it) or the above is
wrong and you need one more blank line. Not enough context to me w/o
looking into the driver code.

>         default:
>                 return -EINVAL;
>         }
>  }

...

> +static int mcp9600_config(struct mcp9600_data *data)
> +{
> +       struct i2c_client *client = data->client;
> +       int ret, cfg;

Why is cfg signed?

> +       cfg  = FIELD_PREP(MCP9600_SENSOR_TYPE_MASK,
> +                         mcp9600_type_map[data->thermocouple_type]);
> +
> +       ret = i2c_smbus_write_byte_data(client, MCP9600_SENSOR_CFG, cfg);
> +       if (ret < 0) {
> +               dev_err(&client->dev, "Failed to set sensor configuration\n");
> +               return ret;
> +       }
> +
> +       return 0;
> +}

...

> +       /* Accept type from dt with default of Type-K. */
> +       data->thermocouple_type = THERMOCOUPLE_TYPE_K;
> +       ret = device_property_read_u32(&client->dev, "thermocouple-type",
> +                                      &data->thermocouple_type);
> +       if (data->thermocouple_type >= ARRAY_SIZE(mcp9600_type_map))
> +               return dev_err_probe(&client->dev, -EINVAL,
> +                                    "Invalid thermocouple-type property %d.\n",

Please, make sure that all printf() specifiers are aligned with the
types of the respective parameters.

> +                                    data->thermocouple_type);

-- 
With Best Regards,
Andy Shevchenko