Re: [PATCH v3] dell-smm-hwmon: Add support for disabling automatic BIOS fan control

[Guenter Roeck]

On 11/17/19 12:02 AM, Giovanni Mascellani wrote:
> Hi,
>
> Il 16/11/19 23:08, Guenter Roeck ha scritto:
> > > +ÂÂÂ mutex_lock(&i8k_mutex);
> > > +ÂÂÂ err = i8k_enable_fan_auto_mode(enable);
> > > +ÂÂÂ mutex_unlock(&i8k_mutex);
> > > +
> > > +ÂÂÂ return err ? -EIO : count;
> >
> > Why override the error code ? i8k_enable_fan_auto_mode()
> > can return -EINVAL.
> >
> > I can see that the rest of the driver has the same bad habit,
> > but that is not a reason to continue it.
>
> Ok, I thought it was the appropriate thing to do just because it was
> done elsewhere. If it's not a good idea, do you think a patch removing
> the other instances of this construct would be appropriate?

In general it is never a good idea to override error codes. "I have seen
it elsewhere" is vener a good argument - you'll find examples for everything
in the Linux kernel.

As for fixing up the other instances in this driver, sure, if you feel like
it, but that would have to be a separate patch.

> > > +}
> > > +
> > >  Â static SENSOR_DEVICE_ATTR_RO(temp1_input, i8k_hwmon_temp, 0);
> > >  Â static SENSOR_DEVICE_ATTR_RO(temp1_label, i8k_hwmon_temp_label, 0);
> > >  Â static SENSOR_DEVICE_ATTR_RO(temp2_input, i8k_hwmon_temp, 1);
> > > @@ -749,12 +794,15 @@ static SENSOR_DEVICE_ATTR_RO(temp10_label,
> > > i8k_hwmon_temp_label, 9);
> > >  Â static SENSOR_DEVICE_ATTR_RO(fan1_input, i8k_hwmon_fan, 0);
> > >  Â static SENSOR_DEVICE_ATTR_RO(fan1_label, i8k_hwmon_fan_label, 0);
> > >  Â static SENSOR_DEVICE_ATTR_RW(pwm1, i8k_hwmon_pwm, 0);
> > > +static SENSOR_DEVICE_ATTR_WO(pwm1_enable, i8k_hwmon_pwm_enable, 0);
> > >  Â static SENSOR_DEVICE_ATTR_RO(fan2_input, i8k_hwmon_fan, 1);
> > >  Â static SENSOR_DEVICE_ATTR_RO(fan2_label, i8k_hwmon_fan_label, 1);
> > >  Â static SENSOR_DEVICE_ATTR_RW(pwm2, i8k_hwmon_pwm, 1);
> > > +static SENSOR_DEVICE_ATTR_WO(pwm2_enable, i8k_hwmon_pwm_enable, 0);
> > >  Â static SENSOR_DEVICE_ATTR_RO(fan3_input, i8k_hwmon_fan, 2);
> > >  Â static SENSOR_DEVICE_ATTR_RO(fan3_label, i8k_hwmon_fan_label, 2);
> > >  Â static SENSOR_DEVICE_ATTR_RW(pwm3, i8k_hwmon_pwm, 2);
> > > +static SENSOR_DEVICE_ATTR_WO(pwm3_enable, i8k_hwmon_pwm_enable, 0);
> >
> > Having three attributes do all the same is not very valuable.
> > I would suggest to stick with pwm1_enable and document that it applies
> > to all pwm channels.
>
> I had no idea what is the convention here. No problem changing this thing.
>
> > > @@ -1200,6 +1291,14 @@ static int __init i8k_probe(void)
> > >  ÂÂÂÂÂ i8k_fan_max = fan_max ? : I8K_FAN_HIGH;ÂÂÂ /* Must not be 0 */
> > >  ÂÂÂÂÂ i8k_pwm_mult = DIV_ROUND_UP(255, i8k_fan_max);
> > >  Â +ÂÂÂ fan_control = dmi_first_match(i8k_whitelist_fan_control);
> > > +ÂÂÂ if (fan_control && fan_control->driver_data) {
> > > +ÂÂÂÂÂÂÂ const struct i8k_fan_control_data *fan_control_data =
> > > fan_control->driver_data;
> > > +ÂÂÂÂÂÂÂ manual_fan = fan_control_data->manual_fan;
> > > +ÂÂÂÂÂÂÂ auto_fan = fan_control_data->auto_fan;
> > > +ÂÂÂÂÂÂÂ pr_info("enabling experimental BIOS fan control support\n");
> >
> > That isn't entirely accurate. What this enables is the ability
> > to select automatic or manual fan control.
>
> Hmm, it sounds right to me: there is a feature which is "BIOS fan
> control" and this driver can "support" it or not, i.e., be aware of it
> and interact with it or not. And all of this is "experimental". The

"experimental" is fine, and I understand that those involved in this
exchange are aware what the message means. It does, however, not help
others not involved.

> wording seems to capture this to me. However, no problem with changing
> it. How would "enabling support for setting automatic/manual fan
> control" work? Can you suggest a wording?

"enabling experimental support for ... " sounds good to me.

Thanks,
Guenter

> Thanks, Giovanni.