From 45e569b558a59837f88d8eda7527d7c50154d75d Mon Sep 17 00:00:00 2001 From: José Miguel Gonçalves Date: Wed, 11 Dec 2013 11:11:13 +0000 Subject: hwmon: HIH-6130: Support I2C bus drivers without I2C_FUNC_SMBUS_QUICK MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit efabcc2123f0ed47870033b8d6fc73b50d76d635 upstream. 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 [Guenter Roeck: Simplified complexity of write_length initialization] Signed-off-by: Guenter Roeck Signed-off-by: Greg Kroah-Hartman --- drivers/hwmon/hih6130.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/drivers/hwmon/hih6130.c b/drivers/hwmon/hih6130.c index 2dc37c7c694..7d68a08baaa 100644 --- a/drivers/hwmon/hih6130.c +++ b/drivers/hwmon/hih6130.c @@ -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: -- cgit v1.2.3-18-g5258