iio: Add si7005 relative humidity and temperature sensor driver

sensor provides 12-bit relative humidity and 14-bit temperature
via I2C interface; temperature and linearity compensation is not
implemented (yet)

driver also supports the Si7015, but not the 2nd generation
sensors Si7013/Si7020/Si7021

datasheet is here
http://www.silabs.com/Support%20Documents/TechnicalDocs/Si7005.pdf

v2: (thanks to Lars-Peter Clausen)
* fix coding style
* use devm_iio_device_register()
* change copyright year to 2014

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Reviewed-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

3 files changed, 200 insertions, 0 deletions

diff --git a/drivers/iio/humidity/Kconfig b/drivers/iio/humidity/Kconfig
index 463c4d9da79e..e116bd8dd0e4 100644
--- a/drivers/iio/humidity/Kconfig
+++ b/drivers/iio/humidity/Kconfig
@@ -12,4 +12,14 @@ config DHT11
           Other sensors should work as well as long as they speak the
           same protocol.
 
+config SI7005
+        tristate "SI7005 relative humidity and temperature sensor"
+        depends on I2C
+        help
+          Say yes here to build support for the Silabs Si7005 relative
+          humidity and temperature sensor.
+
+          To compile this driver as a module, choose M here: the module
+          will be called si7005.
+
 endmenu
diff --git a/drivers/iio/humidity/Makefile b/drivers/iio/humidity/Makefile
index d5d36c0c95f9..e3f3d942e646 100644
--- a/drivers/iio/humidity/Makefile
+++ b/drivers/iio/humidity/Makefile
@@ -3,3 +3,4 @@
 #
 
 obj-$(CONFIG_DHT11) += dht11.o
+obj-$(CONFIG_SI7005) += si7005.o
diff --git a/drivers/iio/humidity/si7005.c b/drivers/iio/humidity/si7005.c
new file mode 100644
index 000000000000..bdd586e6d955
--- /dev/null
+++ b/drivers/iio/humidity/si7005.c
@@ -0,0 +1,189 @@
+/*
+ * si7005.c - Support for Silabs Si7005 humidity and temperature sensor
+ *
+ * Copyright (c) 2014 Peter Meerwald <pmeerw@pmeerw.net>
+ *
+ * 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.
+ *
+ * (7-bit I2C slave address 0x40)
+ *
+ * TODO: heater, fast mode, processed mode (temp. / linearity compensation)
+ */
+
+#include <linux/err.h>
+#include <linux/i2c.h>
+#include <linux/delay.h>
+#include <linux/module.h>
+#include <linux/pm.h>
+
+#include <linux/iio/iio.h>
+#include <linux/iio/sysfs.h>
+
+#define SI7005_STATUS 0x00
+#define SI7005_DATA 0x01 /* 16-bit, MSB */
+#define SI7005_CONFIG 0x03
+#define SI7005_ID 0x11
+
+#define SI7005_STATUS_NRDY BIT(0)
+#define SI7005_CONFIG_TEMP BIT(4)
+#define SI7005_CONFIG_START BIT(0)
+
+#define SI7005_ID_7005 0x50
+#define SI7005_ID_7015 0xf0
+
+struct si7005_data {
+        struct i2c_client *client;
+        struct mutex lock;
+        u8 config;
+};
+
+static int si7005_read_measurement(struct si7005_data *data, bool temp)
+{
+        int tries = 50;
+        int ret;
+
+        mutex_lock(&data->lock);
+
+        ret = i2c_smbus_write_byte_data(data->client, SI7005_CONFIG,
+                data->config | SI7005_CONFIG_START |
+                (temp ? SI7005_CONFIG_TEMP : 0));
+        if (ret < 0)
+                goto done;
+
+        while (tries-- > 0) {
+                msleep(20);
+                ret = i2c_smbus_read_byte_data(data->client, SI7005_STATUS);
+                if (ret < 0)
+                        goto done;
+                if (!(ret & SI7005_STATUS_NRDY))
+                        break;
+        }
+        if (tries < 0) {
+                ret = -EIO;
+                goto done;
+        }
+
+        ret = i2c_smbus_read_word_swapped(data->client, SI7005_DATA);
+
+done:
+        mutex_unlock(&data->lock);
+
+        return ret;
+}
+
+static int si7005_read_raw(struct iio_dev *indio_dev,
+                            struct iio_chan_spec const *chan, int *val,
+                            int *val2, long mask)
+{
+        struct si7005_data *data = iio_priv(indio_dev);
+        int ret;
+
+        switch (mask) {
+        case IIO_CHAN_INFO_RAW:
+                ret = si7005_read_measurement(data, chan->type == IIO_TEMP);
+                if (ret < 0)
+                        return ret;
+                *val = ret;
+                return IIO_VAL_INT;
+        case IIO_CHAN_INFO_SCALE:
+                if (chan->type == IIO_TEMP) {
+                        *val = 7;
+                        *val2 = 812500;
+                } else {
+                        *val = 3;
+                        *val2 = 906250;
+                }
+                return IIO_VAL_INT_PLUS_MICRO;
+        case IIO_CHAN_INFO_OFFSET:
+                if (chan->type == IIO_TEMP)
+                        *val = -50 * 32 * 4;
+                else
+                        *val = -24 * 16 * 16;
+                return IIO_VAL_INT;
+        default:
+                break;
+        }
+
+        return -EINVAL;
+}
+
+static const struct iio_chan_spec si7005_channels[] = {
+        {
+                .type = IIO_HUMIDITYRELATIVE,
+                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+        },
+        {
+                .type = IIO_TEMP,
+                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_OFFSET),
+        }
+};
+
+static const struct iio_info si7005_info = {
+        .read_raw = si7005_read_raw,
+        .driver_module = THIS_MODULE,
+};
+
+static int si7005_probe(struct i2c_client *client,
+                         const struct i2c_device_id *id)
+{
+        struct iio_dev *indio_dev;
+        struct si7005_data *data;
+        int ret;
+
+        if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
+                return -ENODEV;
+
+        indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
+        if (!indio_dev)
+                return -ENOMEM;
+
+        data = iio_priv(indio_dev);
+        i2c_set_clientdata(client, indio_dev);
+        data->client = client;
+        mutex_init(&data->lock);
+
+        indio_dev->dev.parent = &client->dev;
+        indio_dev->name = dev_name(&client->dev);
+        indio_dev->modes = INDIO_DIRECT_MODE;
+        indio_dev->info = &si7005_info;
+
+        indio_dev->channels = si7005_channels;
+        indio_dev->num_channels = ARRAY_SIZE(si7005_channels);
+
+        ret = i2c_smbus_read_byte_data(client, SI7005_ID);
+        if (ret < 0)
+                return ret;
+        if (ret != SI7005_ID_7005 && ret != SI7005_ID_7015)
+                return -ENODEV;
+
+        ret = i2c_smbus_read_byte_data(client, SI7005_CONFIG);
+        if (ret < 0)
+                return ret;
+        data->config = ret;
+
+        return devm_iio_device_register(&client->dev, indio_dev);
+}
+
+static const struct i2c_device_id si7005_id[] = {
+        { "si7005", 0 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, si7005_id);
+
+static struct i2c_driver si7005_driver = {
+        .driver = {
+                .name   = "si7005",
+                .owner  = THIS_MODULE,
+        },
+        .probe = si7005_probe,
+        .id_table = si7005_id,
+};
+module_i2c_driver(si7005_driver);
+
+MODULE_AUTHOR("Peter Meerwald <pmeerw@pmeerw.net>");
+MODULE_DESCRIPTION("Silabs Si7005 humidity and temperature sensor driver");
+MODULE_LICENSE("GPL");