[3.11.y.z extended stable] Patch "hwmon: HIH-6130: Support I2C bus drivers without I2C_FUNC_SMBUS_QUICK" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

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

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 5855d3381f60e745c7a21e85fcbfd250b76fe5d0 Mon Sep 17 00:00:00 2001
From: José Miguel Gonçalves <jose.goncalves at inov.pt>
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 <jose.goncalves at inov.pt>
[Guenter Roeck: Simplified complexity of write_length initialization]
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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..7d68a08 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:
--
1.8.3.2