Subject: Re: [lm-sensors] [PATCH] hwmon: (tmp421) Add nfactor support (2nd attempt)

From: Jeff Angielski <[email-masked]>
Date: Tue, 18 May 2010 10:35:21 -0400

On 05/18/2010 07:38 AM, Andre Prendel wrote:

> I'd prefer starting i with 0 and as condition i < data->channels - 1.
> 
> for (i = 0; i < data->channels -1; i++) {
> 	data->nfactor[i] = i2c_smbus_read_byte_data(client,
> 		TMP421_NFACTOR[i]);
> }
> 
> What do you think?

The first channel is the local channel which does not support nfactor,
so we skip it.  Having the for loop start at 1 illustrates this concept.

> Indentation of the arguments is wrong (see other functions).

Should be fixed in the patch below.  

I am not sure why the patch file itself still shows the function arguments 
off by one.  When I apply it to a raw tmp421.c all of the arguments 
line up correctly.

After rebasing the changes, I am creating the patch as:

$ git format-patch -1 HEAD

Pretty simple stuff...

>>From 467c74e1d8118e34e84a150f18b5e55c6593c777 Mon Sep 17 00:00:00 2001
From: Jeff Angielski <[email-masked]>
Date: Mon, 10 May 2010 10:26:34 -0400
Subject: [PATCH] hwmon: (tmp421) Add nfactor support

Add support for reading and writing the n-factor correction
registers.  This is needed to compensate for the characteristics
of a particular sensor hanging off of the remote channels.

Signed-off-by: Jeff Angielski <[email-masked]>
---
 drivers/hwmon/tmp421.c |   41 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 41 insertions(+), 0 deletions(-)

diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
index 738c472..7944627 100644
--- a/drivers/hwmon/tmp421.c
+++ b/drivers/hwmon/tmp421.c
@@ -49,6 +49,7 @@ enum chips { tmp421, tmp422, tmp423 };
 
 static const u8 TMP421_TEMP_MSB[4]		= { 0x00, 0x01, 0x02, 0x03 };
 static const u8 TMP421_TEMP_LSB[4]		= { 0x10, 0x11, 0x12, 0x13 };
+static const u8 TMP421_NFACTOR[3]		= { 0x21, 0x22, 0x23 };
 
 /* Flags */
 #define TMP421_CONFIG_SHUTDOWN			0x40
@@ -76,6 +77,7 @@ struct tmp421_data {
 	int channels;
 	u8 config;
 	s16 temp[4];
+	s8 nfactor[3];
 };
 
 static int temp_from_s16(s16 reg)
@@ -115,6 +117,10 @@ static struct tmp421_data *tmp421_update_device(struct device *dev)
 			data->temp[i] |= i2c_smbus_read_byte_data(client,
 				TMP421_TEMP_LSB[i]);
 		}
+		for (i = 1; i < data->channels; i++) {
+			data->nfactor[i - 1] = i2c_smbus_read_byte_data(client,
+				TMP421_NFACTOR[i - 1]);
+		}
 		data->last_updated = jiffies;
 		data->valid = 1;
 	}
@@ -157,6 +163,32 @@ static ssize_t show_fault(struct device *dev,
 		return sprintf(buf, "0\n");
 }
 
+static ssize_t show_nfactor(struct device *dev,
+			    struct device_attribute *devattr, char *buf)
+{
+	int index = to_sensor_dev_attr(devattr)->index;
+	struct tmp421_data *data = tmp421_update_device(dev);
+
+	return sprintf(buf, "%d\n", data->nfactor[index - 1]);
+}
+
+static ssize_t set_nfactor(struct device *dev,
+			   struct device_attribute *devattr,
+			   const char *buf, size_t count)
+{
+	struct i2c_client *client = to_i2c_client(dev);
+	struct tmp421_data *data = i2c_get_clientdata(client);
+	int index = to_sensor_dev_attr(devattr)->index;
+	int nfactor = simple_strtol(buf, NULL, 10);
+
+	mutex_lock(&data->update_lock);
+	i2c_smbus_write_byte_data(client, TMP421_NFACTOR[index - 1],
+				  SENSORS_LIMIT(nfactor, -128, 127));
+	mutex_unlock(&data->update_lock);
+
+	return count;
+}
+
 static mode_t tmp421_is_visible(struct kobject *kobj, struct attribute *a,
 				int n)
 {
@@ -177,19 +209,28 @@ static mode_t tmp421_is_visible(struct kobject *kobj, struct attribute *a,
 static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, show_temp_value, NULL, 0);
 static SENSOR_DEVICE_ATTR(temp2_input, S_IRUGO, show_temp_value, NULL, 1);
 static SENSOR_DEVICE_ATTR(temp2_fault, S_IRUGO, show_fault, NULL, 1);
+static SENSOR_DEVICE_ATTR(temp2_nfactor, S_IRUSR | S_IWUSR | S_IRGRP,
+			  show_nfactor, set_nfactor, 1);
 static SENSOR_DEVICE_ATTR(temp3_input, S_IRUGO, show_temp_value, NULL, 2);
 static SENSOR_DEVICE_ATTR(temp3_fault, S_IRUGO, show_fault, NULL, 2);
+static SENSOR_DEVICE_ATTR(temp3_nfactor, S_IRUSR | S_IWUSR | S_IRGRP,
+			  show_nfactor, set_nfactor, 2);
 static SENSOR_DEVICE_ATTR(temp4_input, S_IRUGO, show_temp_value, NULL, 3);
 static SENSOR_DEVICE_ATTR(temp4_fault, S_IRUGO, show_fault, NULL, 3);
+static SENSOR_DEVICE_ATTR(temp4_nfactor, S_IRUSR | S_IWUSR | S_IRGRP,
+			  show_nfactor, set_nfactor, 3);
 
 static struct attribute *tmp421_attr[] = {
 	&sensor_dev_attr_temp1_input.dev_attr.attr,
 	&sensor_dev_attr_temp2_input.dev_attr.attr,
 	&sensor_dev_attr_temp2_fault.dev_attr.attr,
+	&sensor_dev_attr_temp2_nfactor.dev_attr.attr,
 	&sensor_dev_attr_temp3_input.dev_attr.attr,
 	&sensor_dev_attr_temp3_fault.dev_attr.attr,
+	&sensor_dev_attr_temp3_nfactor.dev_attr.attr,
 	&sensor_dev_attr_temp4_input.dev_attr.attr,
 	&sensor_dev_attr_temp4_fault.dev_attr.attr,
+	&sensor_dev_attr_temp4_nfactor.dev_attr.attr,
 	NULL
 };
 
-- 
1.7.0.4

-- 
Jeff Angielski
The PTR Group
www.theptrgroup.com