Commit efabcc21 authored by José Miguel Gonçalves's avatar José Miguel Gonçalves Committed by Guenter Roeck
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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: default avatarJosé Miguel Gonçalves <jose.goncalves@inov.pt>
[Guenter Roeck: Simplified complexity of write_length initialization]
Cc: stable@vger.kernel.org # v3.10+
Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 374b1057

drivers/hwmon/hih6130.c

+14 −2
Original line number Diff line number Diff line
@@ -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:

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