This patch adds a hwmon driver for the SHT4x Temperature and
Humidity sensor.
Signed-off-by: Navin Sankar Velliangiri <[email protected]>
Changes in v2:
* Removed unused macro SHT4X_MIN_POLL_INTERVAL
* Replaced time_after instead of ktime_after
* Used goto statements for error handling
* Hardcoded the interval_time instead of clamp_val().
Changes in v3:
* Accept the poll interval if it is greater than SHT4X_MIN_POLL_INTERVAL and
return -EINVAL for negative values & less than SHT4X_MIN_POLL_INTERVAL
* Changed the data type of update_interval and last_updated to long.
Changes in v4:
* "update_interval" is long but msecs_to_jiffies() accepts only unsigned int.
clamp_val() api is used to assign the update_interval stays within UINT_MAX.
Changes in v5:
* Added error handling when master unable to send the data.
Changes in v6:
* clamp_val() alone is used to set the update interval. since the update
interval is a continuous setting.
---
Documentation/hwmon/index.rst | 1 +
Documentation/hwmon/sht4x.rst | 45 +++++
drivers/hwmon/Kconfig | 11 ++
drivers/hwmon/Makefile | 1 +
drivers/hwmon/sht4x.c | 305 ++++++++++++++++++++++++++++++++++
5 files changed, 363 insertions(+)
create mode 100644 Documentation/hwmon/sht4x.rst
create mode 100644 drivers/hwmon/sht4x.c
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 9ed60fa84cbe..b6fcae40258c 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -164,6 +164,7 @@ Hardware Monitoring Kernel Drivers
sht15
sht21
sht3x
+ sht4x
shtc1
sis5595
sl28cpld
diff --git a/Documentation/hwmon/sht4x.rst b/Documentation/hwmon/sht4x.rst
new file mode 100644
index 000000000000..3b37abcd4a46
--- /dev/null
+++ b/Documentation/hwmon/sht4x.rst
@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Kernel driver sht4x
+===================
+
+Supported Chips:
+
+ * Sensirion SHT4X
+
+ Prefix: 'sht4x'
+
+ Addresses scanned: None
+
+ Datasheet:
+
+ English: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHT4x_Datasheet.pdf
+
+Author: Navin Sankar Velliangiri <[email protected]>
+
+
+Description
+-----------
+
+This driver implements support for the Sensirion SHT4x chip, a humidity
+and temperature sensor. Temperature is measured in degree celsius, relative
+humidity is expressed as a percentage. In sysfs interface, all values are
+scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
+
+Usage Notes
+-----------
+
+The device communicates with the I2C protocol. Sensors can have the I2C
+address 0x44. See Documentation/i2c/instantiating-devices.rst for methods
+to instantiate the device.
+
+Sysfs entries
+-------------
+
+=============== ============================================
+temp1_input Measured temperature in millidegrees Celcius
+humidity1_input Measured humidity in %H
+update_interval The minimum interval for polling the sensor,
+ in milliseconds. Writable. Must be at least
+ 2000.
+============== =============================================
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 87624902ea80..e3675377bc5d 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1583,6 +1583,17 @@ config SENSORS_SHT3x
This driver can also be built as a module. If so, the module
will be called sht3x.
+config SENSORS_SHT4x
+ tristate "Sensiron humidity and temperature sensors. SHT4x and compat."
+ depends on I2C
+ select CRC8
+ help
+ If you say yes here you get support for the Sensiron SHT40, SHT41 and
+ SHT45 humidity and temperature sensors.
+
+ This driver can also be built as a module. If so, the module
+ will be called sht4x.
+
config SENSORS_SHTC1
tristate "Sensiron humidity and temperature sensors. SHTC1 and compat."
depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 59e78bc212cf..d712c61c1f5e 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -171,6 +171,7 @@ obj-$(CONFIG_SENSORS_SL28CPLD) += sl28cpld-hwmon.o
obj-$(CONFIG_SENSORS_SHT15) += sht15.o
obj-$(CONFIG_SENSORS_SHT21) += sht21.o
obj-$(CONFIG_SENSORS_SHT3x) += sht3x.o
+obj-$(CONFIG_SENSORS_SHT4x) += sht4x.o
obj-$(CONFIG_SENSORS_SHTC1) += shtc1.o
obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o
obj-$(CONFIG_SENSORS_SMM665) += smm665.o
diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
new file mode 100644
index 000000000000..39e1b4a123fa
--- /dev/null
+++ b/drivers/hwmon/sht4x.c
@@ -0,0 +1,305 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+/*
+ * Copyright (c) Linumiz 2021
+ *
+ * sht4x.c - Linux hwmon driver for SHT4x Temperature and Humidity sensor
+ *
+ * Author: Navin Sankar Velliangiri <[email protected]>
+ */
+
+#include <linux/crc8.h>
+#include <linux/delay.h>
+#include <linux/hwmon.h>
+#include <linux/i2c.h>
+#include <linux/jiffies.h>
+#include <linux/module.h>
+
+/*
+ * Poll intervals (in milliseconds)
+ */
+#define SHT4X_MIN_POLL_INTERVAL 2000
+
+/*
+ * I2C command delays (in microseconds)
+ */
+#define SHT4X_MEAS_DELAY 1000
+#define SHT4X_DELAY_EXTRA 10000
+
+/*
+ * Command Bytes
+ */
+#define SHT4X_CMD_MEASURE_HPM 0b11111101
+#define SHT4X_CMD_RESET 0b10010100
+
+#define SHT4X_CMD_LEN 1
+#define SHT4X_CRC8_LEN 1
+#define SHT4X_WORD_LEN 2
+#define SHT4X_RESPONSE_LENGTH 6
+#define SHT4X_CRC8_POLYNOMIAL 0x31
+#define SHT4X_CRC8_INIT 0xff
+#define SHT4X_MIN_TEMPERATURE -45000
+#define SHT4X_MAX_TEMPERATURE 125000
+#define SHT4X_MIN_HUMIDITY 0
+#define SHT4X_MAX_HUMIDITY 100000
+
+DECLARE_CRC8_TABLE(sht4x_crc8_table);
+
+/**
+ * struct sht4x_data - All the data required to operate an SHT4X chip
+ * @client: the i2c client associated with the SHT4X
+ * @lock: a mutex that is used to prevent parallel access to the i2c client
+ * @update_interval: the minimum poll interval
+ * @last_updated: the previous time that the SHT4X was polled
+ * @temperature: the latest temperature value received from the SHT4X
+ * @humidity: the latest humidity value received from the SHT4X
+ */
+struct sht4x_data {
+ struct i2c_client *client;
+ struct mutex lock; /* atomic read data updates */
+ bool valid; /* validity of fields below */
+ long update_interval; /* in milli-seconds */
+ long last_updated; /* in jiffies */
+ s32 temperature;
+ s32 humidity;
+};
+
+/**
+ * sht4x_read_values() - read and parse the raw data from the SHT4X
+ * @sht4x_data: the struct sht4x_data to use for the lock
+ * Return: 0 if succesfull, 1 if not
+ */
+static int sht4x_read_values(struct sht4x_data *data)
+{
+ int ret;
+ u16 t_ticks, rh_ticks;
+ unsigned long next_update;
+ struct i2c_client *client = data->client;
+ u8 crc, raw_data[SHT4X_RESPONSE_LENGTH],
+ cmd[] = {SHT4X_CMD_MEASURE_HPM};
+
+ mutex_lock(&data->lock);
+ next_update = data->last_updated +
+ msecs_to_jiffies(data->update_interval);
+ if (!data->valid || time_after(jiffies, next_update)) {
+ ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
+ if (ret < 0)
+ goto unlock;
+
+ usleep_range(SHT4X_MEAS_DELAY,
+ SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
+
+ ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
+ if (ret != SHT4X_RESPONSE_LENGTH) {
+ if (ret >= 0)
+ ret = -ENODATA;
+
+ goto unlock;
+ }
+
+ t_ticks = raw_data[0] << 8 | raw_data[1];
+ rh_ticks = raw_data[3] << 8 | raw_data[4];
+
+ crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
+ if (crc != raw_data[2]) {
+ dev_err(&client->dev, "data integrity check failed\n");
+ ret = -EIO;
+ goto unlock;
+ }
+
+ crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
+ if (crc != raw_data[5]) {
+ dev_err(&client->dev, "data integrity check failed\n");
+ ret = -EIO;
+ goto unlock;
+ }
+
+ data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
+ data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
+ data->last_updated = jiffies;
+ data->valid = true;
+ }
+
+unlock:
+ mutex_unlock(&data->lock);
+ return ret;
+}
+
+static ssize_t sht4x_interval_write(struct sht4x_data *data,
+ long val)
+{
+
+ data->update_interval = clamp_val(val, SHT4X_MIN_POLL_INTERVAL,
+ UINT_MAX);
+
+ return 0;
+}
+
+/**
+ * sht4x_interval_read() - read the minimum poll interval
+ * in milliseconds
+ */
+static size_t sht4x_interval_read(struct sht4x_data *data,
+ long *val)
+{
+ *val = data->update_interval;
+ return 0;
+}
+
+/**
+ * sht4x_temperature1_read() - read the temperature in millidegrees
+ */
+static int sht4x_temperature1_read(struct sht4x_data *data, long *val)
+{
+ int ret;
+
+ ret = sht4x_read_values(data);
+ if (ret < 0)
+ return ret;
+
+ *val = data->temperature;
+
+ return 0;
+}
+
+/**
+ * sht4x_humidity1_read() - read a relative humidity in millipercent
+ */
+static int sht4x_humidity1_read(struct sht4x_data *data, long *val)
+{
+ int ret;
+
+ ret = sht4x_read_values(data);
+ if (ret < 0)
+ return ret;
+
+ *val = data->humidity;
+
+ return 0;
+}
+
+static umode_t sht4x_hwmon_visible(const void *data,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel)
+{
+ switch (type) {
+ case hwmon_temp:
+ case hwmon_humidity:
+ return 0444;
+ case hwmon_chip:
+ return 0644;
+ default:
+ return 0;
+ }
+}
+
+static int sht4x_hwmon_read(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long *val)
+{
+ struct sht4x_data *data = dev_get_drvdata(dev);
+
+ switch (type) {
+ case hwmon_temp:
+ return sht4x_temperature1_read(data, val);
+ case hwmon_humidity:
+ return sht4x_humidity1_read(data, val);
+ case hwmon_chip:
+ return sht4x_interval_read(data, val);
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
+static int sht4x_hwmon_write(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long val)
+{
+ struct sht4x_data *data = dev_get_drvdata(dev);
+
+ switch (type) {
+ case hwmon_chip:
+ return sht4x_interval_write(data, val);
+ default:
+ return -EOPNOTSUPP;
+ }
+}
+
+static const struct hwmon_channel_info *sht4x_info[] = {
+ HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
+ HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT),
+ HWMON_CHANNEL_INFO(humidity, HWMON_H_INPUT),
+ NULL,
+};
+
+static const struct hwmon_ops sht4x_hwmon_ops = {
+ .is_visible = sht4x_hwmon_visible,
+ .read = sht4x_hwmon_read,
+ .write = sht4x_hwmon_write,
+};
+
+static const struct hwmon_chip_info sht4x_chip_info = {
+ .ops = &sht4x_hwmon_ops,
+ .info = sht4x_info,
+};
+
+static int sht4x_probe(struct i2c_client *client,
+ const struct i2c_device_id *sht4x_id)
+{
+ struct device *device = &client->dev;
+ struct device *hwmon_dev;
+ struct sht4x_data *data;
+ u8 cmd[] = {SHT4X_CMD_RESET};
+ int ret;
+
+ /*
+ * we require full i2c support since the sht4x uses multi-byte read and
+ * writes as well as multi-byte commands which are not supported by
+ * the smbus protocol
+ */
+ if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
+ return -EOPNOTSUPP;
+
+ data = devm_kzalloc(device, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->update_interval = SHT4X_MIN_POLL_INTERVAL;
+ data->client = client;
+
+ mutex_init(&data->lock);
+
+ crc8_populate_msb(sht4x_crc8_table, SHT4X_CRC8_POLYNOMIAL);
+
+ ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
+ if (ret < 0)
+ return ret;
+ if (ret != SHT4X_CMD_LEN)
+ return -EIO;
+
+ hwmon_dev = devm_hwmon_device_register_with_info(device,
+ client->name,
+ data,
+ &sht4x_chip_info,
+ NULL);
+
+ return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id sht4x_id[] = {
+ { "sht4x", 0 },
+ { },
+};
+MODULE_DEVICE_TABLE(i2c, sht4x_id);
+
+static struct i2c_driver sht4x_driver = {
+ .driver = {
+ .name = "sht4x",
+ },
+ .probe = sht4x_probe,
+ .id_table = sht4x_id,
+};
+
+module_i2c_driver(sht4x_driver);
+
+MODULE_AUTHOR("Navin Sankar Velliangiri <[email protected]>");
+MODULE_DESCRIPTION("Sensirion SHT4x humidity and temperature sensor driver");
+MODULE_LICENSE("GPL v2");
--
2.31.1
Hi Navin,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on hwmon/hwmon-next]
[also build test WARNING on v5.13-rc2 next-20210521]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Navin-Sankar-Velliangiri/hwmon-Add-sht4x-Temperature-and-Humidity-Sensor-Driver/20210522-232201
base: https://git.kernel.org/pub/scm/linux/kernel/git/groeck/linux-staging.git hwmon-next
config: x86_64-randconfig-r033-20210523 (attached as .config)
compiler: clang version 13.0.0 (https://github.com/llvm/llvm-project e84a9b9bb3051c35dea993cdad7b3d2575638f85)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
# https://github.com/0day-ci/linux/commit/a122a0f7b0de4be7208671bb4f68ee1e14a3f28e
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Navin-Sankar-Velliangiri/hwmon-Add-sht4x-Temperature-and-Humidity-Sensor-Driver/20210522-232201
git checkout a122a0f7b0de4be7208671bb4f68ee1e14a3f28e
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email protected]>
All warnings (new ones prefixed by >>):
>> drivers/hwmon/sht4x.c:84:2: warning: variable 'ret' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
if (!data->valid || time_after(jiffies, next_update)) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler.h:56:28: note: expanded from macro 'if'
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler.h:58:30: note: expanded from macro '__trace_if_var'
#define __trace_if_var(cond) (__builtin_constant_p(cond) ? (cond) : __trace_if_value(cond))
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/hwmon/sht4x.c:125:9: note: uninitialized use occurs here
return ret;
^~~
drivers/hwmon/sht4x.c:84:2: note: remove the 'if' if its condition is always true
if (!data->valid || time_after(jiffies, next_update)) {
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/compiler.h:56:23: note: expanded from macro 'if'
#define if(cond, ...) if ( __trace_if_var( !!(cond , ## __VA_ARGS__) ) )
^
drivers/hwmon/sht4x.c:74:9: note: initialize the variable 'ret' to silence this warning
int ret;
^
= 0
1 warning generated.
vim +84 drivers/hwmon/sht4x.c
66
67 /**
68 * sht4x_read_values() - read and parse the raw data from the SHT4X
69 * @sht4x_data: the struct sht4x_data to use for the lock
70 * Return: 0 if succesfull, 1 if not
71 */
72 static int sht4x_read_values(struct sht4x_data *data)
73 {
74 int ret;
75 u16 t_ticks, rh_ticks;
76 unsigned long next_update;
77 struct i2c_client *client = data->client;
78 u8 crc, raw_data[SHT4X_RESPONSE_LENGTH],
79 cmd[] = {SHT4X_CMD_MEASURE_HPM};
80
81 mutex_lock(&data->lock);
82 next_update = data->last_updated +
83 msecs_to_jiffies(data->update_interval);
> 84 if (!data->valid || time_after(jiffies, next_update)) {
85 ret = i2c_master_send(client, cmd, SHT4X_CMD_LEN);
86 if (ret < 0)
87 goto unlock;
88
89 usleep_range(SHT4X_MEAS_DELAY,
90 SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
91
92 ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
93 if (ret != SHT4X_RESPONSE_LENGTH) {
94 if (ret >= 0)
95 ret = -ENODATA;
96
97 goto unlock;
98 }
99
100 t_ticks = raw_data[0] << 8 | raw_data[1];
101 rh_ticks = raw_data[3] << 8 | raw_data[4];
102
103 crc = crc8(sht4x_crc8_table, &raw_data[0], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
104 if (crc != raw_data[2]) {
105 dev_err(&client->dev, "data integrity check failed\n");
106 ret = -EIO;
107 goto unlock;
108 }
109
110 crc = crc8(sht4x_crc8_table, &raw_data[3], SHT4X_WORD_LEN, CRC8_INIT_VALUE);
111 if (crc != raw_data[5]) {
112 dev_err(&client->dev, "data integrity check failed\n");
113 ret = -EIO;
114 goto unlock;
115 }
116
117 data->temperature = ((21875 * (int32_t)t_ticks) >> 13) - 45000;
118 data->humidity = ((15625 * (int32_t)rh_ticks) >> 13) - 6000;
119 data->last_updated = jiffies;
120 data->valid = true;
121 }
122
123 unlock:
124 mutex_unlock(&data->lock);
125 return ret;
126 }
127
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]
On 5/21/21 11:09 PM, Navin Sankar Velliangiri wrote:
> This patch adds a hwmon driver for the SHT4x Temperature and
> Humidity sensor.
>
> Signed-off-by: Navin Sankar Velliangiri <[email protected]>
>
> Changes in v2:
>
> * Removed unused macro SHT4X_MIN_POLL_INTERVAL
> * Replaced time_after instead of ktime_after
> * Used goto statements for error handling
> * Hardcoded the interval_time instead of clamp_val().
>
> Changes in v3:
>
> * Accept the poll interval if it is greater than SHT4X_MIN_POLL_INTERVAL and
> return -EINVAL for negative values & less than SHT4X_MIN_POLL_INTERVAL
> * Changed the data type of update_interval and last_updated to long.
>
> Changes in v4:
>
> * "update_interval" is long but msecs_to_jiffies() accepts only unsigned int.
> clamp_val() api is used to assign the update_interval stays within UINT_MAX.
>
> Changes in v5:
>
> * Added error handling when master unable to send the data.
>
> Changes in v6:
>
> * clamp_val() alone is used to set the update interval. since the update
> interval is a continuous setting.
> ---
> Documentation/hwmon/index.rst | 1 +
> Documentation/hwmon/sht4x.rst | 45 +++++
> drivers/hwmon/Kconfig | 11 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/sht4x.c | 305 ++++++++++++++++++++++++++++++++++
> 5 files changed, 363 insertions(+)
> create mode 100644 Documentation/hwmon/sht4x.rst
> create mode 100644 drivers/hwmon/sht4x.c
>
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 9ed60fa84cbe..b6fcae40258c 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -164,6 +164,7 @@ Hardware Monitoring Kernel Drivers
> sht15
> sht21
> sht3x
> + sht4x
> shtc1
> sis5595
> sl28cpld
> diff --git a/Documentation/hwmon/sht4x.rst b/Documentation/hwmon/sht4x.rst
> new file mode 100644
> index 000000000000..3b37abcd4a46
> --- /dev/null
> +++ b/Documentation/hwmon/sht4x.rst
> @@ -0,0 +1,45 @@
> +.. SPDX-License-Identifier: GPL-2.0
> +
> +Kernel driver sht4x
> +===================
> +
> +Supported Chips:
> +
> + * Sensirion SHT4X
> +
> + Prefix: 'sht4x'
> +
> + Addresses scanned: None
> +
> + Datasheet:
> +
> + English: https://www.sensirion.com/fileadmin/user_upload/customers/sensirion/Dokumente/2_Humidity_Sensors/Datasheets/Sensirion_Humidity_Sensors_SHT4x_Datasheet.pdf
> +
> +Author: Navin Sankar Velliangiri <[email protected]>
> +
> +
> +Description
> +-----------
> +
> +This driver implements support for the Sensirion SHT4x chip, a humidity
> +and temperature sensor. Temperature is measured in degree celsius, relative
> +humidity is expressed as a percentage. In sysfs interface, all values are
> +scaled by 1000, i.e. the value for 31.5 degrees celsius is 31500.
> +
> +Usage Notes
> +-----------
> +
> +The device communicates with the I2C protocol. Sensors can have the I2C
> +address 0x44. See Documentation/i2c/instantiating-devices.rst for methods
> +to instantiate the device.
> +
> +Sysfs entries
> +-------------
> +
> +=============== ============================================
> +temp1_input Measured temperature in millidegrees Celcius
> +humidity1_input Measured humidity in %H
> +update_interval The minimum interval for polling the sensor,
> + in milliseconds. Writable. Must be at least
> + 2000.
> +============== =============================================
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 87624902ea80..e3675377bc5d 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -1583,6 +1583,17 @@ config SENSORS_SHT3x
> This driver can also be built as a module. If so, the module
> will be called sht3x.
>
> +config SENSORS_SHT4x
> + tristate "Sensiron humidity and temperature sensors. SHT4x and compat."
> + depends on I2C
> + select CRC8
> + help
> + If you say yes here you get support for the Sensiron SHT40, SHT41 and
> + SHT45 humidity and temperature sensors.
> +
> + This driver can also be built as a module. If so, the module
> + will be called sht4x.
> +
> config SENSORS_SHTC1
> tristate "Sensiron humidity and temperature sensors. SHTC1 and compat."
> depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 59e78bc212cf..d712c61c1f5e 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -171,6 +171,7 @@ obj-$(CONFIG_SENSORS_SL28CPLD) += sl28cpld-hwmon.o
> obj-$(CONFIG_SENSORS_SHT15) += sht15.o
> obj-$(CONFIG_SENSORS_SHT21) += sht21.o
> obj-$(CONFIG_SENSORS_SHT3x) += sht3x.o
> +obj-$(CONFIG_SENSORS_SHT4x) += sht4x.o
> obj-$(CONFIG_SENSORS_SHTC1) += shtc1.o
> obj-$(CONFIG_SENSORS_SIS5595) += sis5595.o
> obj-$(CONFIG_SENSORS_SMM665) += smm665.o
> diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
> new file mode 100644
> index 000000000000..39e1b4a123fa
> --- /dev/null
> +++ b/drivers/hwmon/sht4x.c
> @@ -0,0 +1,305 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +/*
> + * Copyright (c) Linumiz 2021
> + *
> + * sht4x.c - Linux hwmon driver for SHT4x Temperature and Humidity sensor
> + *
> + * Author: Navin Sankar Velliangiri <[email protected]>
> + */
> +
> +#include <linux/crc8.h>
> +#include <linux/delay.h>
> +#include <linux/hwmon.h>
> +#include <linux/i2c.h>
> +#include <linux/jiffies.h>
> +#include <linux/module.h>
> +
> +/*
> + * Poll intervals (in milliseconds)
> + */
> +#define SHT4X_MIN_POLL_INTERVAL 2000
> +
> +/*
> + * I2C command delays (in microseconds)
> + */
> +#define SHT4X_MEAS_DELAY 1000
> +#define SHT4X_DELAY_EXTRA 10000
> +
> +/*
> + * Command Bytes
> + */
> +#define SHT4X_CMD_MEASURE_HPM 0b11111101
> +#define SHT4X_CMD_RESET 0b10010100
> +
> +#define SHT4X_CMD_LEN 1
> +#define SHT4X_CRC8_LEN 1
> +#define SHT4X_WORD_LEN 2
> +#define SHT4X_RESPONSE_LENGTH 6
> +#define SHT4X_CRC8_POLYNOMIAL 0x31
> +#define SHT4X_CRC8_INIT 0xff
> +#define SHT4X_MIN_TEMPERATURE -45000
> +#define SHT4X_MAX_TEMPERATURE 125000
> +#define SHT4X_MIN_HUMIDITY 0
> +#define SHT4X_MAX_HUMIDITY 100000
> +
> +DECLARE_CRC8_TABLE(sht4x_crc8_table);
> +
> +/**
> + * struct sht4x_data - All the data required to operate an SHT4X chip
> + * @client: the i2c client associated with the SHT4X
> + * @lock: a mutex that is used to prevent parallel access to the i2c client
> + * @update_interval: the minimum poll interval
> + * @last_updated: the previous time that the SHT4X was polled
> + * @temperature: the latest temperature value received from the SHT4X
> + * @humidity: the latest humidity value received from the SHT4X
> + */
> +struct sht4x_data {
> + struct i2c_client *client;
> + struct mutex lock; /* atomic read data updates */
> + bool valid; /* validity of fields below */
> + long update_interval; /* in milli-seconds */
> + long last_updated; /* in jiffies */
> + s32 temperature;
> + s32 humidity;
> +};
> +
> +/**
> + * sht4x_read_values() - read and parse the raw data from the SHT4X
> + * @sht4x_data: the struct sht4x_data to use for the lock
> + * Return: 0 if succesfull, 1 if not
> + */
> +static int sht4x_read_values(struct sht4x_data *data)
> +{
> + int ret;
Ah yes, the value of ret will be uninitialized, and the function will return
a random value if data->valid is false or if two measurements follow each other.
Please fix and resubmit. The driver looks good otherwise.
Guenter