Subject: Re: [PATCH] hwmon: (tmp421) Add nfactor support.

From: Jean Delvare <[email-masked]>
Date: Tue, 11 May 2010 21:12:19 +0200

On Tue, 11 May 2010 21:03:27 +0200, Andre Prendel wrote:
> On Mon, May 10, 2010 at 10:43:07AM -0400, Jeff Angielski wrote:
> 
> Hi Jeff,
> 
> A few comments below.
>  
> > 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 |   42 ++++++++++++++++++++++++++++++++++++++++++
> >  1 files changed, 42 insertions(+), 0 deletions(-)
> > 
> > diff --git a/drivers/hwmon/tmp421.c b/drivers/hwmon/tmp421.c
> > index 738c472..c9e9855 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
> > @@ -157,6 +158,38 @@ 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)
> > +{
> > +	struct i2c_client *client = to_i2c_client(dev);
> > +	struct tmp421_data *data = i2c_get_clientdata(client);
> > +	int index = to_sensor_dev_attr(devattr)->index;
> > +	s8 nfactor;
> > +
> > +	mutex_lock(&data->update_lock);
> > +	nfactor = i2c_smbus_read_byte_data(client, TMP421_NFACTOR[index-1]);
> 
> There should be spaces within the array index, [index - 1].
> 
> > +	mutex_unlock(&data->update_lock);
> > +
> > +	return sprintf(buf, "%d\n", nfactor);
> > +}
> 
> I'de prefer implementing the sysfs access methods in a consistent way (see other functions). That means adding the nfactor register to the tmp421_data structure and using tmp421_update_device() to update the structure.
> 
> > +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],
> 
> Missing spaces in array index again.
> 
> > +			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 +210,28 @@ 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_IRUGO | S_IWUSR,
> > +		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_IRUGO | S_IWUSR,
> > +		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_IRUGO | S_IWUSR,
> > +		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
> >  };

Any hope to standardize on the sysfs attribute files and units? So that
other drivers can implement the same interface.

-- 
Jean Delvare