linux-kernel - [PATCH] hwmon: HIH-6130: Support I2C bus drivers without I2C_FUNC_SMBUS

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Date:	Wed, 11 Dec 2013 00:57:42 +0000
From:	José Miguel Gonçalves 
	<jose.goncalves@...v.pt>
To:	Jean Delvare <khali@...ux-fr.org>,
	Guenter Roeck <guenter.roeck@...csson.com>,
	lm-sensors@...sensors.org, linux-kernel@...r.kernel.org
Cc:	José Miguel Gonçalves 
	<jose.goncalves@...v.pt>
Subject: [PATCH] hwmon: HIH-6130: Support I2C bus drivers without I2C_FUNC_SMBUS_QUICK

Some I2C bus drivers do not allow zero-lenght data transfers which are
required to start a mesurement 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@...v.pt>
---
 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 2dc37c7..a860cc4 100644
--- a/drivers/hwmon/hih6130.c
+++ b/drivers/hwmon/hih6130.c
@@ -121,8 +121,20 @@ 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.
+		 */
+		if (i2c_get_functionality(client->adapter) &
+		    I2C_FUNC_SMBUS_QUICK) {
+			ret = i2c_master_send(client, tmp, 0);
+		} else {
+			tmp[0] = 0;
+			ret = i2c_master_send(client, tmp, 1);
+		}
 		if (ret < 0)
 			goto out;
 
-- 
1.7.10.4

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