linux-kernel - Re: [PATCH 2/3] hwmon: (adt7475) fan stall prevention

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Date:   Wed, 3 May 2017 00:07:50 +0000
From:   Chris Packham <Chris.Packham@...iedtelesis.co.nz>
To:     Guenter Roeck <linux@...ck-us.net>
CC:     "linux-hwmon@...r.kernel.org" <linux-hwmon@...r.kernel.org>,
        Jean Delvare <jdelvare@...e.com>,
        Jonathan Corbet <corbet@....net>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] hwmon: (adt7475) fan stall prevention

On 03/05/17 06:07, Guenter Roeck wrote:
> On Tue, May 02, 2017 at 05:45:35PM +1200, Chris Packham wrote:
>> By default adt7475 will stop the fans (pwm duty cycle 0%) when the
>> temperature drops past Tmin - hysteresis. Some systems want to keep the
>> fans moving even when the temperature drops so add new sysfs attributes
>> that configure the enhanced acoustics min 1-3 which allows the fans to
>> run at the minimum configure pwm duty cycle.
>>
>> Signed-off-by: Chris Packham <chris.packham@...iedtelesis.co.nz>
>> ---
>> pwmN_min is a horrible name but I really can't think of anything better.
>> I'm biased a little because that is essentially the name of the bits in
>> the datasheet. I'm open to suggestions.
>
> pwmX_min is also traditionally the mimimum permitted pwm value,
> not a boolean. This would be more appropriate to reflect the PWMmin
> register values (0x64 to 0x66). Similar for pwmX_max if you want to
> add support for it.

For the adt7476 driver these are used as pwmN_auto_point[12]_pwm.

> It might make sense to combine pwmX_min==0 with clearing the
> respective bit in the REG_ENHANCE_ACOUSTICS[12] register. This way
> we would only need one attribute to support both.

I could add code such that if pwmN_auto_point1_pwm > 0. The bit in 
REG_ENHANCE_ACOUSTICS is set but that would be a change in existing 
behaviour.