[lm-sensors] [PATCH v3 2/3] hwmon: (lm95241) Fix negative

[lm-sensors] [PATCH v3 2/3] hwmon: (lm95241) Fix negative

[Guenter Roeck]

Negative temperatures were returned in degrees C instead of milli-Degrees C.
Also, negative temperatures were reported for remote temperature sensors even
if the chip was configured for positive-only results.

Fix by detecting temperature modes, and by treating negative temperatures
similar to positive temperatures, with appropriate sign extension.

Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
---
Candidate for -stable.

 drivers/hwmon/lm95241.c |   20 ++++++++++++++------
 1 files changed, 14 insertions(+), 6 deletions(-)

diff --git a/drivers/hwmon/lm95241.c b/drivers/hwmon/lm95241.c
index 01c638e..ec02e30 100644
--- a/drivers/hwmon/lm95241.c
+++ b/drivers/hwmon/lm95241.c
@@ -98,11 +98,16 @@ struct lm95241_data {
 };
 
 /* Conversions */
-static int TempFromReg(u8 val_h, u8 val_l)
+static int temp_from_reg_signed(u8 val_h, u8 val_l)
 {
-	if (val_h & 0x80)
-		return val_h - 0x100;
-	return val_h * 1000 + val_l * 1000 / 256;
+	s16 val_hl = (val_h << 8) | val_l;
+	return val_hl * 1000 / 256;
+}
+
+static int temp_from_reg_unsigned(u8 val_h, u8 val_l)
+{
+	u16 val_hl = (val_h << 8) | val_l;
+	return val_hl * 1000 / 256;
 }
 
 static struct lm95241_data *lm95241_update_device(struct device *dev)
@@ -135,10 +140,13 @@ static ssize_t show_input(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
 	struct lm95241_data *data = lm95241_update_device(dev);
+	int index = to_sensor_dev_attr(attr)->index;
 
 	return snprintf(buf, PAGE_SIZE - 1, "%d\n",
-		TempFromReg(data->temp[to_sensor_dev_attr(attr)->index],
-			    data->temp[to_sensor_dev_attr(attr)->index + 1]));
+			!index || (data->config & index) ?
+		temp_from_reg_signed(data->temp[index], data->temp[index + 1]) :
+		temp_from_reg_unsigned(data->temp[index],
+				       data->temp[index + 1]));
 }
 
 static ssize_t show_type(struct device *dev, struct device_attribute *attr,
-- 
1.7.3.1


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Re: [lm-sensors] [PATCH v3 2/3] hwmon: (lm95241) Fix negative

[Jean Delvare]

Hi Guenter,

On Thu, 7 Jul 2011 13:42:44 -0700, Guenter Roeck wrote:
> Negative temperatures were returned in degrees C instead of milli-Degrees C.
> Also, negative temperatures were reported for remote temperature sensors even
> if the chip was configured for positive-only results.
> 
> Fix by detecting temperature modes, and by treating negative temperatures
> similar to positive temperatures, with appropriate sign extension.
> 
> Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
> ---
> Candidate for -stable.
> 
>  drivers/hwmon/lm95241.c |   20 ++++++++++++++------
>  1 files changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/hwmon/lm95241.c b/drivers/hwmon/lm95241.c
> index 01c638e..ec02e30 100644
> --- a/drivers/hwmon/lm95241.c
> +++ b/drivers/hwmon/lm95241.c
> @@ -98,11 +98,16 @@ struct lm95241_data {
>  };
>  
>  /* Conversions */
> -static int TempFromReg(u8 val_h, u8 val_l)
> +static int temp_from_reg_signed(u8 val_h, u8 val_l)
>  {
> -	if (val_h & 0x80)
> -		return val_h - 0x100;
> -	return val_h * 1000 + val_l * 1000 / 256;
> +	s16 val_hl = (val_h << 8) | val_l;
> +	return val_hl * 1000 / 256;
> +}
> +
> +static int temp_from_reg_unsigned(u8 val_h, u8 val_l)
> +{
> +	u16 val_hl = (val_h << 8) | val_l;
> +	return val_hl * 1000 / 256;
>  }
>  
>  static struct lm95241_data *lm95241_update_device(struct device *dev)
> @@ -135,10 +140,13 @@ static ssize_t show_input(struct device *dev, struct device_attribute *attr,
>  			  char *buf)
>  {
>  	struct lm95241_data *data = lm95241_update_device(dev);
> +	int index = to_sensor_dev_attr(attr)->index;
>  
>  	return snprintf(buf, PAGE_SIZE - 1, "%d\n",
> -		TempFromReg(data->temp[to_sensor_dev_attr(attr)->index],
> -			    data->temp[to_sensor_dev_attr(attr)->index + 1]));
> +			!index || (data->config & index) ?

Hmm. This really should be:

+			!index || (data->config & (1 << (index / 2))) ?

It just _happens_ that (1 << (index / 2)) = index for index values 2
and 4, so your code works. But if we ever add support for a compatible
device with an extra temperature channel, it'll break. Not sure if the
rest of the driver code would properly cope with such a change anyway,
though.

Furthermore, I think that readability could be slightly improved by
changing "!index" to "index = 0", as this is neither an error
condition nor a boolean).

Readability could be improved even more with driver-wide changes but
this is obviously out-of-scope for this patch.

> +		temp_from_reg_signed(data->temp[index], data->temp[index + 1]) :
> +		temp_from_reg_unsigned(data->temp[index],
> +				       data->temp[index + 1]));
>  }
>  
>  static ssize_t show_type(struct device *dev, struct device_attribute *attr,

-- 
Jean Delvare

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Re: [lm-sensors] [PATCH v3 2/3] hwmon: (lm95241) Fix negative

[Guenter Roeck]

Hi Jean,

On Sat, Jul 09, 2011 at 04:36:18PM -0400, Jean Delvare wrote:
> Hi Guenter,
> 
> On Thu, 7 Jul 2011 13:42:44 -0700, Guenter Roeck wrote:
> > Negative temperatures were returned in degrees C instead of milli-Degrees C.
> > Also, negative temperatures were reported for remote temperature sensors even
> > if the chip was configured for positive-only results.
> > 
> > Fix by detecting temperature modes, and by treating negative temperatures
> > similar to positive temperatures, with appropriate sign extension.
> > 
> > Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com>
> > ---
> > Candidate for -stable.
> > 
> >  drivers/hwmon/lm95241.c |   20 ++++++++++++++------
> >  1 files changed, 14 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/hwmon/lm95241.c b/drivers/hwmon/lm95241.c
> > index 01c638e..ec02e30 100644
> > --- a/drivers/hwmon/lm95241.c
> > +++ b/drivers/hwmon/lm95241.c
> > @@ -98,11 +98,16 @@ struct lm95241_data {
> >  };
> >  
> >  /* Conversions */
> > -static int TempFromReg(u8 val_h, u8 val_l)
> > +static int temp_from_reg_signed(u8 val_h, u8 val_l)
> >  {
> > -	if (val_h & 0x80)
> > -		return val_h - 0x100;
> > -	return val_h * 1000 + val_l * 1000 / 256;
> > +	s16 val_hl = (val_h << 8) | val_l;
> > +	return val_hl * 1000 / 256;
> > +}
> > +
> > +static int temp_from_reg_unsigned(u8 val_h, u8 val_l)
> > +{
> > +	u16 val_hl = (val_h << 8) | val_l;
> > +	return val_hl * 1000 / 256;
> >  }
> >  
> >  static struct lm95241_data *lm95241_update_device(struct device *dev)
> > @@ -135,10 +140,13 @@ static ssize_t show_input(struct device *dev, struct device_attribute *attr,
> >  			  char *buf)
> >  {
> >  	struct lm95241_data *data = lm95241_update_device(dev);
> > +	int index = to_sensor_dev_attr(attr)->index;
> >  
> >  	return snprintf(buf, PAGE_SIZE - 1, "%d\n",
> > -		TempFromReg(data->temp[to_sensor_dev_attr(attr)->index],
> > -			    data->temp[to_sensor_dev_attr(attr)->index + 1]));
> > +			!index || (data->config & index) ?
> 
> Hmm. This really should be:
> 
> +			!index || (data->config & (1 << (index / 2))) ?
> 
> It just _happens_ that (1 << (index / 2)) = index for index values 2
> and 4, so your code works. But if we ever add support for a compatible
> device with an extra temperature channel, it'll break. Not sure if the
> rest of the driver code would properly cope with such a change anyway,
> though.
> 
> Furthermore, I think that readability could be slightly improved by
> changing "!index" to "index = 0", as this is neither an error
> condition nor a boolean).
> 
Makes sense. I changed it to

		index = 0 || (data->config & (1 << (index / 2)))

> Readability could be improved even more with driver-wide changes but
> this is obviously out-of-scope for this patch.
> 
Yes, I know. Another time, maybe.

Thanks,
Guenter

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