[lm-sensors] [PATCH v2] hwmon: (max31722) Add support for MAX31722/MAX31723 temperature sensors

Discussion:

Tiberiu Breana

2016-03-28 14:15:57 UTC

Add basic support for the Maxim Integrated MAX31722/MAX31723 SPI
temperature sensors / thermostats.

Includes:
- ACPI support;
- raw temperature readings;
- power management

Datasheet:
https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf

Signed-off-by: Tiberiu Breana <***@intel.com>
---
Changes from v1:
- addressed Guenter's comments
- removed regmap
- set resolution to 12 bits
---
Documentation/hwmon/max31722 | 34 ++++++++
drivers/hwmon/Kconfig | 11 +++
drivers/hwmon/Makefile | 1 +
drivers/hwmon/max31722.c | 182 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 228 insertions(+)
create mode 100644 Documentation/hwmon/max31722
create mode 100644 drivers/hwmon/max31722.c

diff --git a/Documentation/hwmon/max31722 b/Documentation/hwmon/max31722
new file mode 100644
index 0000000..090da845
--- /dev/null
+++ b/Documentation/hwmon/max31722
@@ -0,0 +1,34 @@
+Kernel driver max31722
+======================
+
+Supported chips:
+ * Maxim Integrated MAX31722
+ Prefix: 'max31722'
+ ACPI ID: MAX31722
+ Addresses scanned: -
+ Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
+ * Maxim Integrated MAX31723
+ Prefix: 'max31723'
+ ACPI ID: MAX31723
+ Addresses scanned: -
+ Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
+
+Author: Tiberiu Breana <***@intel.com>
+
+Description
+-----------
+
+This driver adds support for the Maxim Integrated MAX31722/MAX31723 thermometers
+and thermostats running over an SPI interface.
+
+Usage Notes
+-----------
+
+This driver uses ACPI to auto-detect devices. See ACPI IDs in the above section.
+
+Sysfs entries
+-------------
+
+The following attribute is supported:
+
+temp1_input Measured temperature. Read-only.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 60fb80b..b819312 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -807,6 +807,17 @@ config SENSORS_MAX197
This driver can also be built as a module. If so, the module
will be called max197.

+config SENSORS_MAX31722
+tristate "MAX31722 temperature sensor"
+ depends on SPI
+ select REGMAP_SPI
+ help
+ Support for the Maxim Integrated MAX31722/MAX31723 digital
+ thermometers/thermostats operating over an SPI interface.
+
+ This driver can also be built as a module. If so, the module
+ will be called max31722.
+
config SENSORS_MAX6639
tristate "Maxim MAX6639 sensor chip"
depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 30c94df..689afe9 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -111,6 +111,7 @@ obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
obj-$(CONFIG_SENSORS_MAX197) += max197.o
+obj-$(CONFIG_SENSORS_MAX31722) += max31722.o
obj-$(CONFIG_SENSORS_MAX6639) += max6639.o
obj-$(CONFIG_SENSORS_MAX6642) += max6642.o
obj-$(CONFIG_SENSORS_MAX6650) += max6650.o
diff --git a/drivers/hwmon/max31722.c b/drivers/hwmon/max31722.c
new file mode 100644
index 0000000..b3606d9
--- /dev/null
+++ b/drivers/hwmon/max31722.c
@@ -0,0 +1,182 @@
+/*
+ * max31722 - hwmon driver for Maxim Integrated MAX31722/MAX31723 SPI
+ * digital thermometer and thermostats.
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License. See the file COPYING in the main
+ * directory of this archive for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+
+#define MAX31722_REG_CFG 0x00
+#define MAX31722_REG_TEMP_LSB 0x01
+
+#define MAX31722_MODE_CONTINUOUS 0x00
+#define MAX31722_MODE_STANDBY 0x01
+#define MAX31722_MODE_MASK 0xFE
+#define MAX31722_RESOLUTION_12BIT 0x06
+#define MAX31722_12BIT_STEP 62
+#define MAX31722_WRITE_MASK 0x80
+
+struct max31722_data {
+ struct device *hwmon_dev;
+ struct spi_device *spi_device;
+ u8 mode;
+};
+
+static int max31722_set_mode(struct max31722_data *data, u8 mode)
+{
+ int ret;
+ struct spi_device *spi = data->spi_device;
+ u8 buf[2] = {
+ MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+ (data->mode & MAX31722_MODE_MASK) | mode
+ };
+
+ ret = spi_write(spi, &buf, sizeof(buf));
+
+ if (ret < 0) {
+ dev_err(&spi->dev, "failed to set sensor mode.\n");
+ return ret;
+ }
+ data->mode = (data->mode & MAX31722_MODE_MASK) | mode;
+
+ return 0;
+}
+
+static ssize_t max31722_show_temp(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ u16 temp;
+ struct max31722_data *data = dev_get_drvdata(dev);
+
+ temp = spi_w8r16(data->spi_device, MAX31722_REG_TEMP_LSB);
+ if (temp < 0)
+ return temp;
+ /* Keep 12 bits and multiply by the scale of 62 millidegrees/bit. */
+ return sprintf(buf, "%d\n",
+ ((s16)le16_to_cpu(temp) >> 4) * MAX31722_12BIT_STEP);
+}
+
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
+ max31722_show_temp, NULL, 0);
+
+static struct attribute *max31722_attrs[] = {
+ &sensor_dev_attr_temp1_input.dev_attr.attr,
+ NULL,
+};
+
+ATTRIBUTE_GROUPS(max31722);
+
+static int max31722_probe(struct spi_device *spi)
+{
+ int ret;
+ struct max31722_data *data;
+ /*
+ * Set SD bit to 0 so we can have continuous measurements.
+ * Set resolution to 12 bits for maximum precision.
+ */
+ u8 mode = MAX31722_MODE_CONTINUOUS | MAX31722_RESOLUTION_12BIT;
+ u8 init_buf[2] = {
+ MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+ mode
+ };
+
+ data = devm_kzalloc(&spi->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ spi_set_drvdata(spi, data);
+ data->spi_device = spi;
+ ret = spi_write(spi, &init_buf, sizeof(init_buf));
+ if (ret < 0) {
+ max31722_set_mode(data, MAX31722_MODE_STANDBY);
+ return ret;
+ }
+ data->mode = mode;
+
+ data->hwmon_dev =
+ devm_hwmon_device_register_with_groups(&spi->dev,
+ spi->modalias,
+ data,
+ max31722_groups);
+ if (IS_ERR(data->hwmon_dev)) {
+ max31722_set_mode(data, MAX31722_MODE_STANDBY);
+ return PTR_ERR(data->hwmon_dev);
+ }
+
+ return 0;
+}
+
+static int max31722_remove(struct spi_device *spi)
+{
+ struct max31722_data *data = spi_get_drvdata(spi);
+
+ hwmon_device_unregister(data->hwmon_dev);
+
+ return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int max31722_suspend(struct device *dev)
+{
+ struct spi_device *spi_device = to_spi_device(dev);
+ struct max31722_data *data = spi_get_drvdata(spi_device);
+
+ return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+static int max31722_resume(struct device *dev)
+{
+ struct spi_device *spi_device = to_spi_device(dev);
+ struct max31722_data *data = spi_get_drvdata(spi_device);
+
+ return max31722_set_mode(data, MAX31722_MODE_CONTINUOUS);
+}
+
+static SIMPLE_DEV_PM_OPS(max31722_pm_ops, max31722_suspend, max31722_resume);
+
+#define MAX31722_PM_OPS (&max31722_pm_ops)
+#else
+#define MAX31722_PM_OPS NULL
+#endif
+
+static const struct spi_device_id max31722_spi_id[] = {
+ {"max31722", 0},
+ {"max31723", 0},
+ {}
+};
+
+static const struct acpi_device_id max31722_acpi_id[] = {
+ {"MAX31722", 0},
+ {"MAX31723", 0},
+ {}
+};
+
+MODULE_DEVICE_TABLE(spi, max31722_spi_id);
+
+static struct spi_driver max31722_driver = {
+ .driver = {
+ .name = "max31722",
+ .pm = MAX31722_PM_OPS,
+ .acpi_match_table = ACPI_PTR(max31722_acpi_id),
+ },
+ .probe = max31722_probe,
+ .remove = max31722_remove,
+ .id_table = max31722_spi_id,
+};
+
+module_spi_driver(max31722_driver);
+
+MODULE_AUTHOR("Tiberiu Breana <***@intel.com>");
+MODULE_DESCRIPTION("max31722 sensor driver");
+MODULE_LICENSE("GPL v2");

--
1.9.1

Guenter Roeck

2016-03-29 15:44:32 UTC

Permalink

Post by Tiberiu Breana
Add basic support for the Maxim Integrated MAX31722/MAX31723 SPI
temperature sensors / thermostats.
- ACPI support;
- raw temperature readings;
- power management
https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
---
- addressed Guenter's comments
- removed regmap

Why ? Just wondering.

Did you drop patch #2, or is it going to come later ?

More comments below.

Thanks,
Guenter

Post by Tiberiu Breana
- set resolution to 12 bits
---
Documentation/hwmon/max31722 | 34 ++++++++
drivers/hwmon/Kconfig | 11 +++
drivers/hwmon/Makefile | 1 +
drivers/hwmon/max31722.c | 182 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 228 insertions(+)
create mode 100644 Documentation/hwmon/max31722
create mode 100644 drivers/hwmon/max31722.c
diff --git a/Documentation/hwmon/max31722 b/Documentation/hwmon/max31722
new file mode 100644
index 0000000..090da845
--- /dev/null
+++ b/Documentation/hwmon/max31722
@@ -0,0 +1,34 @@
+Kernel driver max31722
+======================
+
+ * Maxim Integrated MAX31722
+ Prefix: 'max31722'
+ ACPI ID: MAX31722
+ Addresses scanned: -
+ Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
+ * Maxim Integrated MAX31723
+ Prefix: 'max31723'
+ ACPI ID: MAX31723
+ Addresses scanned: -
+ Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX31722-MAX31723.pdf
+
+
+Description
+-----------
+
+This driver adds support for the Maxim Integrated MAX31722/MAX31723 thermometers
+and thermostats running over an SPI interface.
+
+Usage Notes
+-----------
+
+This driver uses ACPI to auto-detect devices. See ACPI IDs in the above section.
+
+Sysfs entries
+-------------
+
+
+temp1_input Measured temperature. Read-only.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 60fb80b..b819312 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -807,6 +807,17 @@ config SENSORS_MAX197
This driver can also be built as a module. If so, the module
will be called max197.
+config SENSORS_MAX31722
+tristate "MAX31722 temperature sensor"
+ depends on SPI
+ select REGMAP_SPI

You dropped regmap, so this should no longer be necessary.

Post by Tiberiu Breana
+ help
+ Support for the Maxim Integrated MAX31722/MAX31723 digital
+ thermometers/thermostats operating over an SPI interface.
+
+ This driver can also be built as a module. If so, the module
+ will be called max31722.
+
config SENSORS_MAX6639
tristate "Maxim MAX6639 sensor chip"
depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 30c94df..689afe9 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -111,6 +111,7 @@ obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
obj-$(CONFIG_SENSORS_MAX197) += max197.o
+obj-$(CONFIG_SENSORS_MAX31722) += max31722.o
obj-$(CONFIG_SENSORS_MAX6639) += max6639.o
obj-$(CONFIG_SENSORS_MAX6642) += max6642.o
obj-$(CONFIG_SENSORS_MAX6650) += max6650.o
diff --git a/drivers/hwmon/max31722.c b/drivers/hwmon/max31722.c
new file mode 100644
index 0000000..b3606d9
--- /dev/null
+++ b/drivers/hwmon/max31722.c
@@ -0,0 +1,182 @@
+/*
+ * max31722 - hwmon driver for Maxim Integrated MAX31722/MAX31723 SPI
+ * digital thermometer and thermostats.
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License. See the file COPYING in the main
+ * directory of this archive for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>

Please lust include files in alphabetic order; that makes it easier
to make changes later.

Post by Tiberiu Breana
+
+#define MAX31722_REG_CFG 0x00
+#define MAX31722_REG_TEMP_LSB 0x01
+
+#define MAX31722_MODE_CONTINUOUS 0x00
+#define MAX31722_MODE_STANDBY 0x01
+#define MAX31722_MODE_MASK 0xFE
+#define MAX31722_RESOLUTION_12BIT 0x06
+#define MAX31722_12BIT_STEP 62
+#define MAX31722_WRITE_MASK 0x80
+
+struct max31722_data {
+ struct device *hwmon_dev;
+ struct spi_device *spi_device;
+ u8 mode;
+};
+
+static int max31722_set_mode(struct max31722_data *data, u8 mode)
+{
+ int ret;
+ struct spi_device *spi = data->spi_device;
+ u8 buf[2] = {
+ MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+ (data->mode & MAX31722_MODE_MASK) | mode
+ };
+
+ ret = spi_write(spi, &buf, sizeof(buf));
+

Please drop this empty line.

Post by Tiberiu Breana
+ if (ret < 0) {
+ dev_err(&spi->dev, "failed to set sensor mode.\n");
+ return ret;
+ }
+ data->mode = (data->mode & MAX31722_MODE_MASK) | mode;
+
+ return 0;
+}
+
+static ssize_t max31722_show_temp(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ u16 temp;
+ struct max31722_data *data = dev_get_drvdata(dev);
+
+ temp = spi_w8r16(data->spi_device, MAX31722_REG_TEMP_LSB);
+ if (temp < 0)
+ return temp;

temp is u16, so this doesn't work.

Post by Tiberiu Breana
+ /* Keep 12 bits and multiply by the scale of 62 millidegrees/bit. */
+ return sprintf(buf, "%d\n",
+ ((s16)le16_to_cpu(temp) >> 4) * MAX31722_12BIT_STEP);

The step width is really 62.5 milli-degrees C, so this introduces an error.
Something like
(s16)le16_to_cpu(temp) * 125 / 32
would be more accurate.

Post by Tiberiu Breana
+}
+
+static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO,
+ max31722_show_temp, NULL, 0);
+
+static struct attribute *max31722_attrs[] = {
+ &sensor_dev_attr_temp1_input.dev_attr.attr,
+ NULL,
+};
+
+ATTRIBUTE_GROUPS(max31722);
+
+static int max31722_probe(struct spi_device *spi)
+{
+ int ret;
+ struct max31722_data *data;
+ /*
+ * Set SD bit to 0 so we can have continuous measurements.
+ * Set resolution to 12 bits for maximum precision.
+ */
+ u8 mode = MAX31722_MODE_CONTINUOUS | MAX31722_RESOLUTION_12BIT;
+ u8 init_buf[2] = {
+ MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+ mode
+ };
+
+ data = devm_kzalloc(&spi->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ spi_set_drvdata(spi, data);
+ data->spi_device = spi;
+ ret = spi_write(spi, &init_buf, sizeof(init_buf));
+ if (ret < 0) {
+ max31722_set_mode(data, MAX31722_MODE_STANDBY);
+ return ret;
+ }
+ data->mode = mode;

Initializing data->mode with
MAX31722_MODE_CONTINUOUS | MAX31722_RESOLUTION_12BIT
and calling
max31722_set_mode(data, MAX31722_MODE_CONTINUOUS);
would accomplish the same with less complexity.

Also, since the write failed, calling max31722_set_mode()
on error (especially with the un-initialized data->mode)
doesn't make much sense. You might as well just return in
that case.

Post by Tiberiu Breana
+
+ data->hwmon_dev =
+ devm_hwmon_device_register_with_groups(&spi->dev,
+ spi->modalias,
+ data,
+ max31722_groups);
+ if (IS_ERR(data->hwmon_dev)) {
+ max31722_set_mode(data, MAX31722_MODE_STANDBY);
+ return PTR_ERR(data->hwmon_dev);
+ }
+
+ return 0;
+}
+
+static int max31722_remove(struct spi_device *spi)
+{
+ struct max31722_data *data = spi_get_drvdata(spi);
+
+ hwmon_device_unregister(data->hwmon_dev);
+

This defeats the purpose of using devm_hwmon_device_register_with_groups().
Please use hwmon_device_register_with_groups() instead.

Post by Tiberiu Breana
+ return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int max31722_suspend(struct device *dev)
+{
+ struct spi_device *spi_device = to_spi_device(dev);
+ struct max31722_data *data = spi_get_drvdata(spi_device);
+
+ return max31722_set_mode(data, MAX31722_MODE_STANDBY);
+}
+
+static int max31722_resume(struct device *dev)
+{
+ struct spi_device *spi_device = to_spi_device(dev);
+ struct max31722_data *data = spi_get_drvdata(spi_device);
+
+ return max31722_set_mode(data, MAX31722_MODE_CONTINUOUS);
+}
+
+static SIMPLE_DEV_PM_OPS(max31722_pm_ops, max31722_suspend, max31722_resume);
+
+#define MAX31722_PM_OPS (&max31722_pm_ops)
+#else
+#define MAX31722_PM_OPS NULL
+#endif

Please drop the #ifdef and tag the functions with __maybe_unused.
While this causes max31722_pm_ops to be defined in the non-PM
case, it ensures that the functions are always compiled.
The benefit outweighs the cost.

Post by Tiberiu Breana
+
+static const struct spi_device_id max31722_spi_id[] = {
+ {"max31722", 0},
+ {"max31723", 0},
+ {}
+};
+
+static const struct acpi_device_id max31722_acpi_id[] = {
+ {"MAX31722", 0},
+ {"MAX31723", 0},
+ {}
+};

I think you may need to tag this array with __maybe_unused to avoid
an unused warning if ACPI is not configured.

Post by Tiberiu Breana
+
+MODULE_DEVICE_TABLE(spi, max31722_spi_id);
+
+static struct spi_driver max31722_driver = {
+ .driver = {
+ .name = "max31722",
+ .pm = MAX31722_PM_OPS,
+ .acpi_match_table = ACPI_PTR(max31722_acpi_id),
+ },
+ .probe = max31722_probe,
+ .remove = max31722_remove,
+ .id_table = max31722_spi_id,
+};
+
+module_spi_driver(max31722_driver);
+
+MODULE_DESCRIPTION("max31722 sensor driver");
+MODULE_LICENSE("GPL v2");
--
1.9.1

Breana, Tiberiu A

2016-03-30 08:59:44 UTC

Permalink

-----Original Message-----
Sent: Tuesday, March 29, 2016 6:45 PM
Subject: Re: [PATCH v2] hwmon: (max31722) Add support for
MAX31722/MAX31723 temperature sensors

MAX31723.pdf

Post by Tiberiu Breana
---
- addressed Guenter's comments
- removed regmap

Why ? Just wondering.

It added a lot of code bloat and not much else.

Did you drop patch #2, or is it going to come later ?

It's coming later.

More comments below.
Thanks,
Guenter

All the suggested changes will be applied in v3 soon.
Thanks,

Tiberiu

Post by Tiberiu Breana
- set resolution to 12 bits
---
Documentation/hwmon/max31722 | 34 ++++++++
drivers/hwmon/Kconfig | 11 +++
drivers/hwmon/Makefile | 1 +
drivers/hwmon/max31722.c | 182

+++++++++++++++++++++++++++++++++++++++++++

Post by Tiberiu Breana
4 files changed, 228 insertions(+)
create mode 100644 Documentation/hwmon/max31722 create mode

100644

Post by Tiberiu Breana
drivers/hwmon/max31722.c
diff --git a/Documentation/hwmon/max31722
b/Documentation/hwmon/max31722 new file mode 100644 index
0000000..090da845
--- /dev/null
+++ b/Documentation/hwmon/max31722
@@ -0,0 +1,34 @@
+Kernel driver max31722
+======================
+
+ * Maxim Integrated MAX31722
+ Prefix: 'max31722'
+ ACPI ID: MAX31722
+ Addresses scanned: -
+https://datasheets.maximintegrated.com/en/ds/MAX31722-

MAX31723.pdf

Post by Tiberiu Breana
+ * Maxim Integrated MAX31723
+ Prefix: 'max31723'
+ ACPI ID: MAX31723
+ Addresses scanned: -
+https://datasheets.maximintegrated.com/en/ds/MAX31722-

MAX31723.pdf

Post by Tiberiu Breana
+
+
+Description
+-----------
+
+This driver adds support for the Maxim Integrated MAX31722/MAX31723
+thermometers and thermostats running over an SPI interface.
+
+Usage Notes
+-----------
+
+This driver uses ACPI to auto-detect devices. See ACPI IDs in the above

section.

Post by Tiberiu Breana
+
+Sysfs entries
+-------------
+
+
+temp1_input Measured temperature. Read-only.
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig index
60fb80b..b819312 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -807,6 +807,17 @@ config SENSORS_MAX197
This driver can also be built as a module. If so, the module
will be called max197.
+config SENSORS_MAX31722
+tristate "MAX31722 temperature sensor"
+ depends on SPI
+ select REGMAP_SPI

You dropped regmap, so this should no longer be necessary.

max16065.o

Post by Tiberiu Breana
obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
obj-$(CONFIG_SENSORS_MAX197) += max197.o
+obj-$(CONFIG_SENSORS_MAX31722) += max31722.o
obj-$(CONFIG_SENSORS_MAX6639) += max6639.o
obj-$(CONFIG_SENSORS_MAX6642) += max6642.o
obj-$(CONFIG_SENSORS_MAX6650) += max6650.o
diff --git a/drivers/hwmon/max31722.c b/drivers/hwmon/max31722.c new
file mode 100644 index 0000000..b3606d9
--- /dev/null
+++ b/drivers/hwmon/max31722.c
@@ -0,0 +1,182 @@
+/*
+ * max31722 - hwmon driver for Maxim Integrated MAX31722/MAX31723

SPI

Post by Tiberiu Breana
+ * digital thermometer and thermostats.
+ *
+ * Copyright (c) 2016, Intel Corporation.
+ *
+ * This file is subject to the terms and conditions of version 2 of
+ * the GNU General Public License. See the file COPYING in the main
+ * directory of this archive for more details.
+ */
+
+#include <linux/kernel.h>
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/spi/spi.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>

Please lust include files in alphabetic order; that makes it easier to make
changes later.

Post by Tiberiu Breana
+
+#define MAX31722_REG_CFG 0x00
+#define MAX31722_REG_TEMP_LSB 0x01
+
+#define MAX31722_MODE_CONTINUOUS 0x00
+#define MAX31722_MODE_STANDBY 0x01
+#define MAX31722_MODE_MASK 0xFE
+#define MAX31722_RESOLUTION_12BIT 0x06
+#define MAX31722_12BIT_STEP 62
+#define MAX31722_WRITE_MASK 0x80
+
+struct max31722_data {
+ struct device *hwmon_dev;
+ struct spi_device *spi_device;
+ u8 mode;
+};
+
+static int max31722_set_mode(struct max31722_data *data, u8 mode) {
+ int ret;
+ struct spi_device *spi = data->spi_device;
+ u8 buf[2] = {
+ MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+ (data->mode & MAX31722_MODE_MASK) | mode
+ };
+
+ ret = spi_write(spi, &buf, sizeof(buf));
+

Please drop this empty line.

temp is u16, so this doesn't work.

Post by Tiberiu Breana
+ /* Keep 12 bits and multiply by the scale of 62 millidegrees/bit. */
+ return sprintf(buf, "%d\n",
+ ((s16)le16_to_cpu(temp) >> 4) * MAX31722_12BIT_STEP);

The step width is really 62.5 milli-degrees C, so this introduces an error.
Something like
(s16)le16_to_cpu(temp) * 125 / 32
would be more accurate.

MAX31722_RESOLUTION_12BIT;

Post by Tiberiu Breana
+ u8 init_buf[2] = {
+ MAX31722_REG_CFG | MAX31722_WRITE_MASK,
+ mode
+ };
+
+ data = devm_kzalloc(&spi->dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ spi_set_drvdata(spi, data);
+ data->spi_device = spi;
+ ret = spi_write(spi, &init_buf, sizeof(init_buf));
+ if (ret < 0) {
+ max31722_set_mode(data, MAX31722_MODE_STANDBY);
+ return ret;
+ }
+ data->mode = mode;

Initializing data->mode with
MAX31722_MODE_CONTINUOUS | MAX31722_RESOLUTION_12BIT and
calling
max31722_set_mode(data, MAX31722_MODE_CONTINUOUS); would
accomplish the same with less complexity.
Also, since the write failed, calling max31722_set_mode() on error (especially
with the un-initialized data->mode) doesn't make much sense. You might as
well just return in that case.

Post by Tiberiu Breana
+
+ data->hwmon_dev =
+ devm_hwmon_device_register_with_groups(&spi->dev,
+ spi->modalias,
+ data,
+ max31722_groups);
+ if (IS_ERR(data->hwmon_dev)) {
+ max31722_set_mode(data, MAX31722_MODE_STANDBY);
+ return PTR_ERR(data->hwmon_dev);
+ }
+
+ return 0;
+}
+
+static int max31722_remove(struct spi_device *spi) {
+ struct max31722_data *data = spi_get_drvdata(spi);
+
+ hwmon_device_unregister(data->hwmon_dev);
+

This defeats the purpose of using
devm_hwmon_device_register_with_groups().
Please use hwmon_device_register_with_groups() instead.

Post by Tiberiu Breana
+ return max31722_set_mode(data, MAX31722_MODE_STANDBY); }
+
+#ifdef CONFIG_PM_SLEEP
+static int max31722_suspend(struct device *dev) {
+ struct spi_device *spi_device = to_spi_device(dev);
+ struct max31722_data *data = spi_get_drvdata(spi_device);
+
+ return max31722_set_mode(data, MAX31722_MODE_STANDBY); }
+
+static int max31722_resume(struct device *dev) {
+ struct spi_device *spi_device = to_spi_device(dev);
+ struct max31722_data *data = spi_get_drvdata(spi_device);
+
+ return max31722_set_mode(data,

MAX31722_MODE_CONTINUOUS); }

Post by Tiberiu Breana
+
+static SIMPLE_DEV_PM_OPS(max31722_pm_ops, max31722_suspend,
+max31722_resume);
+
+#define MAX31722_PM_OPS (&max31722_pm_ops) #else #define
+MAX31722_PM_OPS NULL #endif

Please drop the #ifdef and tag the functions with __maybe_unused.
While this causes max31722_pm_ops to be defined in the non-PM case, it
ensures that the functions are always compiled.
The benefit outweighs the cost.

I think you may need to tag this array with __maybe_unused to avoid an
unused warning if ACPI is not configured.

MODULE_LICENSE("GPL

Post by Tiberiu Breana
+v2");
--
1.9.1