Re: [PATCH] added kernel module for FTS sensor chip "Teutates"

["thilo.cestonaro@ts.fujitsu.com" <thilo.cestonaro@ts.fujitsu.com>]

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Hey Guenter!

Thanks for your patience and very detailed review!
I will change the code to address all you hints where no discussion is needed.
The others follow down here.

On Fr, 2016-06-03 at 22:51 -0700, Guenter Roeck wrote:
> > +#define FTSTEUTATES_WATCHDOG_RESOLUTION		   60
> > +
> 60 seconds (minimum) resolution ? Really ? This is very unusual.
Will double check and talk to the hw guy.

> > +static ssize_t show_fan_fault(struct device *dev,
> > +	struct device_attribute *devattr, char *buf)
> > +{
> > +	int index = to_sensor_dev_attr(devattr)->index;
> > +	struct ftsteutates_data *data = ftsteutates_update_device(dev);
> > +
> > +	return sprintf(buf, "%d\n", data->fan_present[index] == 1 ? 0 : 1);
> A non-present fan does not indicate a fan fault.
For me a fan fault was a not existing fan, as the alarm is handled via fan_alarm.
What is the understanding of fan_fault and fan_alarm?

> > +static ssize_t show_fan_source(struct device *dev,
> > +		struct device_attribute *devattr, char *buf)
> > +{
> > +	int index = to_sensor_dev_attr(devattr)->index;
> > +	struct ftsteutates_data *data = ftsteutates_update_device(dev);
> > +
> > +	if (data->fan_present[index]) {
> > +		if (data->fan_source[index] == 0xFF)
> > +			return sprintf(buf, "none\n");
> > +		else
> > +			return sprintf(buf, "%d\n", data->fan_source[index]);
> > +	} else
> > +		return sprintf(buf, "-\n");
> is_visible() is your friend here. If the fan is not present, don't display
> the attributes. If fan presence can change at runtime, just display 0.
I just tried to change to presence at runtime (pull the fan cable),
and it looks like I don't change. So I'll use the is_visible function of the
sysfs entries. 

> In general though I don't understand what fan presence has to do with
> the the fan source. What is the fan source anyway ? This is a non-standard
> attribute, so you will need to explain why it is needed and what data
> it provides in detail.
The fan source represents the sensor number which actually defines the fan-speed.
And the present or not present check is just to show another value if not present.
Which will be unnecessary when the module uses is_visible.

> > +SENSOR_DEVICE_ATTR(overall_uptime, S_IRUGO, show_overall_uptime, NULL, 0);
> > +
> I am not inclined to accept those (non-standard) attributes unless you make
> a really good case why they are needed.
The chip has this functionality, so I wanted to provide access to it.
If this non-standard "export" of functionality disturbs anyone,
I have no problem with removing it.

> > +	err = watchdog_register_device(&ftsteutates_wdt);
> > +	if (err) {
> > +		dev_err(&client->dev,
> > +			"Registering watchdog device failed: %d\n", err);
> > +		goto exit_detach;
> > +	}
> I don't really like combining those drivers. There should really be a means
> (other than mfd) to write two separate drivers for a chip like this.
> I'll have to research that a bit.
So export the watchdog part into a separate module?
Is the i2c client forwarded to another driver if a driver which uses it was found?

Again thanks for your answers and patience! :)

Cheers,
Thilo

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