Date: Fri, 12 Jul 2013 06:50:00 -0700
From: Guenter Roeck <linux@roeck-us.net>
To: Jean Delvare <khali@linux-fr.org>
Cc: Wei Ni <wni@nvidia.com>, thierry.reding@gmail.com,
        lm-sensors@lm-sensors.org, linux-kernel@vger.kernel.org,
        linux-tegra@vger.kernel.org
Subject: Re: [PATCH v3 1/4] hwmon: (lm90) split set&show temp as common codes
Message-ID: <20130712135000.GA3386@roeck-us.net>
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 <20130712152615.23464a6b@endymion.delvare>
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On Fri, Jul 12, 2013 at 03:26:15PM +0200, Jean Delvare wrote:
> Hi Wei, Guenter,
> 
> Guenter, thanks for reviewing the previous version of this patch.
> 
> Wei, thanks for incorporating review feedback and posting updated
> patches so quickly, this is very appreciated, even though I'm too busy
> these days to be that fast on my end, sorry about that.
> 
> On Fri, 12 Jul 2013 15:48:04 +0800, Wei Ni wrote:
> > Split set&show temp codes as common functions, so we can use it directly when
> > implement linux thermal framework.
> 
> Can I see a recent version of the code which will need this change? It
> makes no sense to apply this first part which makes the code more
> complex with no benefit, without the second part which needs it, so
> they should be applied together or not at all.
> 
> One thing I am a little worried about (but maybe I'm wrong) is that I
> seem to understand you want to register every LM90-like chip as both a
> hwmon device and two thermal devices. I seem to recall that every
> thermal device is also exposed automatically as a virtual hwmon
> device, is that correct? If so we will be presenting the same values
> twice to libsensors, which would be confusing.
> 
Not sure if that is a good idea, but if I recall correctly, the thermal folks
plan to remove that path.

Guenter

> > Signed-off-by: Wei Ni <wni@nvidia.com>
> > ---
> >  drivers/hwmon/lm90.c |  112 +++++++++++++++++++++++++++++++-------------------
> >  1 file changed, 69 insertions(+), 43 deletions(-)
> 
> The code changes look good, however I have one suggestion for
> improvement (plus a minor cleanup request):
> 
> > diff --git a/drivers/hwmon/lm90.c b/drivers/hwmon/lm90.c
> > index 8eeb141..5f30f90 100644
> > --- a/drivers/hwmon/lm90.c
> > +++ b/drivers/hwmon/lm90.c
> > (...)
> > -static ssize_t set_temp8(struct device *dev, struct device_attribute *devattr,
> > -			 const char *buf, size_t count)
> > (...)
> > +static void write_temp8(struct device *dev, int index, long val)
> >  {
> >  	static const u8 reg[8] = {
> >  		LM90_REG_W_LOCAL_LOW,
> > @@ -737,60 +742,73 @@ static ssize_t set_temp8(struct device *dev, struct device_attribute *devattr,
> >  		MAX6659_REG_W_REMOTE_EMERG,
> >  	};
> >  
> > -	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> >  	struct i2c_client *client = to_i2c_client(dev);
> >  	struct lm90_data *data = i2c_get_clientdata(client);
> > -	int nr = attr->index;
> > -	long val;
> > -	int err;
> > -
> > -	err = kstrtol(buf, 10, &val);
> > -	if (err < 0)
> > -		return err;
> >  
> >  	/* +16 degrees offset for temp2 for the LM99 */
> > -	if (data->kind == lm99 && attr->index == 3)
> > +	if (data->kind == lm99 && index == 3)
> >  		val -= 16000;
> >  
> >  	mutex_lock(&data->update_lock);
> >  	if (data->kind == adt7461)
> > -		data->temp8[nr] = temp_to_u8_adt7461(data, val);
> > +		data->temp8[index] = temp_to_u8_adt7461(data, val);
> >  	else if (data->kind == max6646)
> > -		data->temp8[nr] = temp_to_u8(val);
> > +		data->temp8[index] = temp_to_u8(val);
> >  	else
> > -		data->temp8[nr] = temp_to_s8(val);
> > +		data->temp8[index] = temp_to_s8(val);
> >  
> > -	lm90_select_remote_channel(client, data, nr >= 6);
> > -	i2c_smbus_write_byte_data(client, reg[nr], data->temp8[nr]);
> > +	lm90_select_remote_channel(client, data, index >= 6);
> > +	i2c_smbus_write_byte_data(client, reg[index], data->temp8[index]);
> 
> This write could fail. So far the lm90 driver has failed to handle
> register write errors at all, and I will take the blame for that. But
> if we want to integrate properly with the thermal subsystem, I suspect
> we will have to properly report errors. So it might be the right time
> to catch and return write errors here. Then set_temp8() below could
> return it to user-space (either in this patch or in a separate patch,
> as you prefer.)
> 
> And then as a next step, lm90_select_remote_channel should return
> errors as they happen as well, so that they can be transmitted to the
> caller.
> 
> >  	lm90_select_remote_channel(client, data, 0);
> >  
> >  	mutex_unlock(&data->update_lock);
> > +}
> > +
> > +static ssize_t set_temp8(struct device *dev, struct device_attribute *devattr,
> > +			 const char *buf, size_t count)
> > +{
> > +	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> > +	int index = attr->index;
> > +	long val;
> > +	int err;
> > +
> > +	err = kstrtol(buf, 10, &val);
> > +	if (err < 0)
> > +		return err;
> > +
> > +	write_temp8(dev, index, val);
> > +
> >  	return count;
> >  }
> >  
> > -static ssize_t show_temp11(struct device *dev, struct device_attribute *devattr,
> > -			   char *buf)
> > +static int read_temp11(struct device *dev, int index)
> >  {
> > -	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(devattr);
> >  	struct lm90_data *data = lm90_update_device(dev);
> >  	int temp;
> >  
> >  	if (data->kind == adt7461)
> > -		temp = temp_from_u16_adt7461(data, data->temp11[attr->index]);
> > +		temp = temp_from_u16_adt7461(data, data->temp11[index]);
> >  	else if (data->kind == max6646)
> > -		temp = temp_from_u16(data->temp11[attr->index]);
> > +		temp = temp_from_u16(data->temp11[index]);
> >  	else
> > -		temp = temp_from_s16(data->temp11[attr->index]);
> > +		temp = temp_from_s16(data->temp11[index]);
> >  
> >  	/* +16 degrees offset for temp2 for the LM99 */
> > -	if (data->kind == lm99 &&  attr->index <= 2)
> > +	if (data->kind == lm99 &&  index <= 2)
> 
> There's a doubled space on this line. It isn't added by your patch, it
> was already there before, but please fix it while you're here.
> 
> >  		temp += 16000;
> >  
> > -	return sprintf(buf, "%d\n", temp);
> > +	return temp;
> >  }
> >  
> > -static ssize_t set_temp11(struct device *dev, struct device_attribute *devattr,
> > -			  const char *buf, size_t count)
> > (...)
> > +static void write_temp11(struct device *dev, int nr, int index, long val)
> 
> Here too I would suggest returning errors from the I2C layer, and
> handling them in set_temp11() now or later.
> 
> >  {
> >  	struct {
> >  		u8 high;
> > @@ -804,17 +822,8 @@ static ssize_t set_temp11(struct device *dev, struct device_attribute *devattr,
> >  		{ LM90_REG_W_REMOTE_HIGHH, LM90_REG_W_REMOTE_HIGHL, 1 }
> >  	};
> >  
> > -	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(devattr);
> >  	struct i2c_client *client = to_i2c_client(dev);
> >  	struct lm90_data *data = i2c_get_clientdata(client);
> > -	int nr = attr->nr;
> > -	int index = attr->index;
> > -	long val;
> > -	int err;
> > -
> > -	err = kstrtol(buf, 10, &val);
> > -	if (err < 0)
> > -		return err;
> >  
> >  	/* +16 degrees offset for temp2 for the LM99 */
> >  	if (data->kind == lm99 && index <= 2)
> > @@ -839,6 +848,23 @@ static ssize_t set_temp11(struct device *dev, struct device_attribute *devattr,
> >  	lm90_select_remote_channel(client, data, 0);
> >  
> >  	mutex_unlock(&data->update_lock);
> > +}
> > +
> > +static ssize_t set_temp11(struct device *dev, struct device_attribute *devattr,
> > +			  const char *buf, size_t count)
> > +{
> > +	struct sensor_device_attribute_2 *attr = to_sensor_dev_attr_2(devattr);
> > +	int nr = attr->nr;
> > +	int index = attr->index;
> > +	long val;
> > +	int err;
> > +
> > +	err = kstrtol(buf, 10, &val);
> > +	if (err < 0)
> > +		return err;
> > +
> > +	write_temp11(dev, nr, index, val);
> > +
> >  	return count;
> >  }
> >  
> 
> -- 
> Jean Delvare
> 
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