Re: [PATCH 2/3] iio: temperature: add max6675 thermocouple converter driver

[Peter Meerwald]

On Mon, 3 Aug 2015, Matt Porter wrote:

> Add a driver for the MAX6675 thermocouple converter. This
> device interfaces with K-type thermocouples and provides
> cold-junction compensated temperature readings via a
> SPI interface.

comments below
 
> Signed-off-by: Matt Porter <mporter@xxxxxxxxxxxx>
> ---
>  drivers/iio/temperature/Kconfig   |  11 +++
>  drivers/iio/temperature/Makefile  |   1 +
>  drivers/iio/temperature/max6675.c | 155 ++++++++++++++++++++++++++++++++++++++
>  3 files changed, 167 insertions(+)
>  create mode 100644 drivers/iio/temperature/max6675.c
> 
> diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig
> index 21feaa4..b73fbf4 100644
> --- a/drivers/iio/temperature/Kconfig
> +++ b/drivers/iio/temperature/Kconfig
> @@ -3,6 +3,17 @@
>  #
>  menu "Temperature sensors"
>  
> +config MAX6675
> +	tristate "MAX6675 thermocouple converter"
> +	depends on SPI
> +	help
> +	  If you say yes here you get support for the Maxim
> +	  MAX6675 thermocouple converter connected with SPI.
> +
> +	  This driver can also be built as a module. If so, the module will
> +	  be called max6675.
> +

extra newline

> +
>  config MLX90614
>  	tristate "MLX90614 contact-less infrared sensor"
>  	depends on I2C
> diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile
> index 40710a8..d67ef40 100644
> --- a/drivers/iio/temperature/Makefile
> +++ b/drivers/iio/temperature/Makefile
> @@ -2,5 +2,6 @@
>  # Makefile for industrial I/O temperature drivers
>  #
>  
> +obj-$(CONFIG_MAX6675) += max6675.o
>  obj-$(CONFIG_MLX90614) += mlx90614.o
>  obj-$(CONFIG_TMP006) += tmp006.o
> diff --git a/drivers/iio/temperature/max6675.c b/drivers/iio/temperature/max6675.c
> new file mode 100644
> index 0000000..2d1fda2
> --- /dev/null
> +++ b/drivers/iio/temperature/max6675.c
> @@ -0,0 +1,155 @@
> +/*
> + * max6675.c - MAX6675 thermocouple converter driver
> + *
> + * Copyright (C) 2015 Konsulko Group, Matt Porter <mporter@xxxxxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + */
> +
> +#include <linux/acpi.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/iio/iio.h>
> +#include <linux/spi/spi.h>
> +
> +struct max6675_state {
> +	struct spi_device *spi;
> +};
> +
> +static const struct iio_chan_spec max6675_channels[] = {
> +	{
> +		.type = IIO_TEMP,
> +		.info_mask_separate =
> +			BIT(IIO_CHAN_INFO_RAW) |
> +			BIT(IIO_CHAN_INFO_SCALE),
> +	},
> +};
> +
> +static int max6675_read(struct max6675_state *st, int *val)
> +{
> +	int ret;
> +
> +	ret = spi_read(st->spi, val, 2);
> +	if (ret < 0)
> +		return ret;
> +
> +	/* Temperature is bits 14..3 */
> +	*val = (*val >> 3) & 0xfff;

what about endianness conversion?
use be16_to_cpu()

> +
> +	return ret;
> +}
> +
> +static int max6675_read_raw(struct iio_dev *indio_dev,
> +			    struct iio_chan_spec const *chan,
> +			    int *val,
> +			    int *val2,
> +			    long m)
> +{
> +	struct max6675_state *st = iio_priv(indio_dev);
> +	int ret;
> +
> +	if (m == IIO_CHAN_INFO_RAW) {
> +		*val2 = 0;

no need to set *val2 to 0 when returning VAL_INT

> +		ret = max6675_read(st, val);
> +		if (ret)
> +			return ret;
> +	} else if (m == IIO_CHAN_INFO_SCALE) {
> +		*val = 250;
> +		*val2 = 0;
> +	} else
> +		return -EINVAL;
> +
> +	return IIO_VAL_INT;
> +}
> +
> +static const struct iio_info max6675_info = {
> +	.driver_module = THIS_MODULE,
> +	.read_raw = &max6675_read_raw,
> +};
> +
> +static int max6675_probe(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev;
> +	struct max6675_state *st;
> +	int ret = 0;

no need to initialize ret

> +
> +	indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*st));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	st = iio_priv(indio_dev);
> +	st->spi = spi;
> +
> +	spi->mode = SPI_MODE_1;
> +	spi->bits_per_word = 16;
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	indio_dev->dev.parent = &spi->dev;
> +	indio_dev->name = spi_get_device_id(spi)->name;
> +	indio_dev->channels = max6675_channels;
> +	indio_dev->num_channels = ARRAY_SIZE(max6675_channels);
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +	indio_dev->info = &max6675_info;
> +
> +	ret = iio_device_register(indio_dev);

devm_ and drop _remove()

> +	if (ret < 0)
> +		dev_err(&spi->dev, "unable to register device\n");
> +
> +	return ret;
> +}
> +
> +static int max6675_remove(struct spi_device *spi)
> +{
> +	struct iio_dev *indio_dev = spi_get_drvdata(spi);
> +
> +	iio_device_unregister(indio_dev);
> +
> +	return 0;
> +}
> +
> +static const struct acpi_device_id max6675_acpi_ids[] = {
> +	{ "MXIM6675", 0 },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(acpi, max6675_acpi_ids);
> +
> +static const struct of_device_id max6675_dt_ids[] = {
> +	{ .compatible = "maxim,max6675" },
> +	{},
> +};
> +MODULE_DEVICE_TABLE(of, max6675_dt_ids);
> +
> +static const struct spi_device_id max6675_spi_ids[] = {
> +	{"max6675", 0},
> +	{},
> +};
> +MODULE_DEVICE_TABLE(spi, max6675_spi_ids);
> +
> +static struct spi_driver max6675_driver = {
> +	.driver = {
> +		.name	= "max6675",
> +		.owner	= THIS_MODULE,
> +		.acpi_match_table = ACPI_PTR(max6675_acpi_ids),
> +		.of_match_table = of_match_ptr(max6675_dt_ids),
> +	},
> +	.probe		= max6675_probe,
> +	.remove		= max6675_remove,
> +	.id_table	= max6675_spi_ids,
> +};
> +module_spi_driver(max6675_driver);
> +
> +MODULE_AUTHOR("Matt Porter <mporter@xxxxxxxxxxxx>");
> +MODULE_DESCRIPTION("MAX6675 thermocouple converter driver");
> +MODULE_LICENSE("GPL");
> +MODULE_ALIAS("spi:max6675");
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)
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