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authorPeter A. Bigot <pab@pabigot.com>2016-12-24 07:22:44 -0600
committerGuenter Roeck <linux@roeck-us.net>2017-01-02 10:19:45 -0800
commit53e678d75e7c22b251c6981ff8364b5c42c5eac4 (patch)
tree2886d135b167d53686c839802d655b5a312cce25
parent5343aed12f262c87372c4f20b744756837240dc9 (diff)
hwmon: (sht21) Add Electronic Identification Code retrieval
Expose the per-chip unique identifier so it can be used to identify the sensor producing the measurements. Signed-off-by: Peter A. Bigot <pab@pabigot.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
-rw-r--r--Documentation/hwmon/sht215
-rw-r--r--drivers/hwmon/sht21.c92
2 files changed, 93 insertions, 4 deletions
diff --git a/Documentation/hwmon/sht21 b/Documentation/hwmon/sht21
index db17fda45c3e..47f4765db256 100644
--- a/Documentation/hwmon/sht21
+++ b/Documentation/hwmon/sht21
@@ -35,6 +35,7 @@ sysfs-Interface
temp1_input - temperature input
humidity1_input - humidity input
+eic - Electronic Identification Code
Notes
-----
@@ -45,5 +46,5 @@ humidity and 66 ms for temperature. To keep self heating below 0.1 degree
Celsius, the device should not be active for more than 10% of the time,
e.g. maximum two measurements per second at the given resolution.
-Different resolutions, the on-chip heater, using the CRC checksum and reading
-the serial number are not supported yet.
+Different resolutions, the on-chip heater, and using the CRC checksum
+are not supported yet.
diff --git a/drivers/hwmon/sht21.c b/drivers/hwmon/sht21.c
index 84cdb1cf0fb4..06706d288355 100644
--- a/drivers/hwmon/sht21.c
+++ b/drivers/hwmon/sht21.c
@@ -34,23 +34,29 @@
/* I2C command bytes */
#define SHT21_TRIG_T_MEASUREMENT_HM 0xe3
#define SHT21_TRIG_RH_MEASUREMENT_HM 0xe5
+#define SHT21_READ_SNB_CMD1 0xFA
+#define SHT21_READ_SNB_CMD2 0x0F
+#define SHT21_READ_SNAC_CMD1 0xFC
+#define SHT21_READ_SNAC_CMD2 0xC9
/**
* struct sht21 - SHT21 device specific data
* @hwmon_dev: device registered with hwmon
* @lock: mutex to protect measurement values
- * @valid: only 0 before first measurement is taken
* @last_update: time of last update (jiffies)
* @temperature: cached temperature measurement value
* @humidity: cached humidity measurement value
+ * @valid: only 0 before first measurement is taken
+ * @eic: cached electronic identification code text
*/
struct sht21 {
struct i2c_client *client;
struct mutex lock;
- char valid;
unsigned long last_update;
int temperature;
int humidity;
+ char valid;
+ char eic[18];
};
/**
@@ -165,15 +171,97 @@ static ssize_t sht21_show_humidity(struct device *dev,
return sprintf(buf, "%d\n", sht21->humidity);
}
+static ssize_t eic_read(struct sht21 *sht21)
+{
+ struct i2c_client *client = sht21->client;
+ u8 tx[2];
+ u8 rx[8];
+ u8 eic[8];
+ struct i2c_msg msgs[2] = {
+ {
+ .addr = client->addr,
+ .flags = 0,
+ .len = 2,
+ .buf = tx,
+ },
+ {
+ .addr = client->addr,
+ .flags = I2C_M_RD,
+ .len = 8,
+ .buf = rx,
+ },
+ };
+ int ret;
+
+ tx[0] = SHT21_READ_SNB_CMD1;
+ tx[1] = SHT21_READ_SNB_CMD2;
+ ret = i2c_transfer(client->adapter, msgs, 2);
+ if (ret < 0)
+ goto out;
+ eic[2] = rx[0];
+ eic[3] = rx[2];
+ eic[4] = rx[4];
+ eic[5] = rx[6];
+
+ tx[0] = SHT21_READ_SNAC_CMD1;
+ tx[1] = SHT21_READ_SNAC_CMD2;
+ msgs[1].len = 6;
+ ret = i2c_transfer(client->adapter, msgs, 2);
+ if (ret < 0)
+ goto out;
+ eic[0] = rx[3];
+ eic[1] = rx[4];
+ eic[6] = rx[0];
+ eic[7] = rx[1];
+
+ ret = snprintf(sht21->eic, sizeof(sht21->eic),
+ "%02x%02x%02x%02x%02x%02x%02x%02x\n",
+ eic[0], eic[1], eic[2], eic[3],
+ eic[4], eic[5], eic[6], eic[7]);
+out:
+ if (ret < 0)
+ sht21->eic[0] = 0;
+
+ return ret;
+}
+
+/**
+ * eic_show() - show Electronic Identification Code in sysfs
+ * @dev: device
+ * @attr: device attribute
+ * @buf: sysfs buffer (PAGE_SIZE) where EIC is written
+ *
+ * Will be called on read access to eic sysfs attribute.
+ * Returns number of bytes written into buffer, negative errno on error.
+ */
+static ssize_t eic_show(struct device *dev,
+ struct device_attribute *attr,
+ char *buf)
+{
+ struct sht21 *sht21 = dev_get_drvdata(dev);
+ int ret;
+
+ ret = sizeof(sht21->eic) - 1;
+ mutex_lock(&sht21->lock);
+ if (!sht21->eic[0])
+ ret = eic_read(sht21);
+ if (ret > 0)
+ memcpy(buf, sht21->eic, ret);
+ mutex_unlock(&sht21->lock);
+ return ret;
+}
+
/* sysfs attributes */
static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, sht21_show_temperature,
NULL, 0);
static SENSOR_DEVICE_ATTR(humidity1_input, S_IRUGO, sht21_show_humidity,
NULL, 0);
+static DEVICE_ATTR_RO(eic);
static struct attribute *sht21_attrs[] = {
&sensor_dev_attr_temp1_input.dev_attr.attr,
&sensor_dev_attr_humidity1_input.dev_attr.attr,
+ &dev_attr_eic.attr,
NULL
};