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

[Matt Porter <mporter@konsulko.com>]

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.

Signed-off-by: Matt Porter <mporter@konsulko.com>
---
 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.
+
+
 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@konsulko.com>
+ *
+ * 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;
+
+	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;
+		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;
+
+	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);
+	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@konsulko.com>");
+MODULE_DESCRIPTION("MAX6675 thermocouple converter driver");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:max6675");
-- 
2.1.4