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hwmon: HIH-6130: Support I2C bus drivers without I2C_FUNC_SMBUS_QUICK 

Some I2C bus drivers do not allow zero-length data transfers which are
required to start a measurement with the HIH6130/1 sensor. Nevertheless,
we can overcome this limitation by writing a zero dummy byte. This byte
is ignored by the sensor and was verified to be working with the OMAP
I2C bus driver in a BeagleBone board.

Signed-off-by: José Miguel Gonçalves <jose.goncalves@inov.pt>
[Guenter Roeck: Simplified complexity of write_length initialization]
Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
This commit is contained in:
José Miguel Gonçalves 2013-12-11 11:11:13 +00:00 committed by Guenter Roeck
parent 374b105797
commit efabcc2123
1 changed files with 14 additions and 2 deletions
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16
drivers/hwmon/hih6130.c
View File

@ -43,6 +43,7 @@
* @last_update: time of last update (jiffies)
* @temperature: cached temperature measurement value
* @humidity: cached humidity measurement value
* @write_length: length for I2C measurement request
*/
struct hih6130 {
struct device *hwmon_dev;
@ -51,6 +52,7 @@ struct hih6130 {
unsigned long last_update;
int temperature;
int humidity;
size_t write_length;
};
/**
@ -121,8 +123,15 @@ static int hih6130_update_measurements(struct i2c_client *client)
*/
if (time_after(jiffies, hih6130->last_update + HZ) || !hih6130->valid) {
/* write to slave address, no data, to request a measurement */
ret = i2c_master_send(client, tmp, 0);
/*
* Write to slave address to request a measurement.
* According with the datasheet it should be with no data, but
* for systems with I2C bus drivers that do not allow zero
* length packets we write one dummy byte to allow sensor
* measurements on them.
*/
tmp[0] = 0;
ret = i2c_master_send(client, tmp, hih6130->write_length);
if (ret < 0)
goto out;
@ -252,6 +261,9 @@ static int hih6130_probe(struct i2c_client *client,
goto fail_remove_sysfs;
}
if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_QUICK))
hih6130->write_length = 1;
return 0;
fail_remove_sysfs: