[lm-sensors] hwmon and GPIO fan

[lm-sensors] hwmon and GPIO fan

[Simon Guinot]

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Hello,

I am currently looking to add hwmon support for the fan device found on
Network Space Max v2 boards (ARM Kirkwood SoC).

The fan speed can be configured trough GPIOs. The GPIO settings allow to
change the fan input voltage (via some resistors).
After a quick look at the hwmon sysfs interface, I have failed to find
the appropriate way to expose a non-pwm fan. If any, what is the
dedicated sysfs entry to set speed for a non-pwm fan ?
Maybe that a fake pwm interface is needed ?

Thanks in advance.

Simon

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Re: [lm-sensors] hwmon and GPIO fan

[Jean Delvare]

Salut Simon,

On Mon, 11 Oct 2010 14:25:58 +0000, Simon Guinot wrote:
> I am currently looking to add hwmon support for the fan device found on
> Network Space Max v2 boards (ARM Kirkwood SoC).
> 
> The fan speed can be configured trough GPIOs. The GPIO settings allow to
> change the fan input voltage (via some resistors).
> After a quick look at the hwmon sysfs interface, I have failed to find
> the appropriate way to expose a non-pwm fan. If any, what is the
> dedicated sysfs entry to set speed for a non-pwm fan ?
> Maybe that a fake pwm interface is needed ?

Don't let yourself be fooled by the "pwm[1-n]" and "pwm[1_n]_enable"
files names. These are valid for all fan control outputs, be they PWM
or DC. As a matter of fact, "pwm[1-n]_mode" lets you advertise whether
the controller is using PWM or DC.

All that really matters is that you use 0-255 as the pwm[1-n] range
matching 0-100%.

-- 
Jean Delvare

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Re: [lm-sensors] hwmon and GPIO fan

[Simon Guinot]

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On Mon, Oct 11, 2010 at 04:45:32PM +0200, Jean Delvare wrote:
> Salut Simon,
> 
> On Mon, 11 Oct 2010 14:25:58 +0000, Simon Guinot wrote:
> > I am currently looking to add hwmon support for the fan device found on
> > Network Space Max v2 boards (ARM Kirkwood SoC).
> > 
> > The fan speed can be configured trough GPIOs. The GPIO settings allow to
> > change the fan input voltage (via some resistors).
> > After a quick look at the hwmon sysfs interface, I have failed to find
> > the appropriate way to expose a non-pwm fan. If any, what is the
> > dedicated sysfs entry to set speed for a non-pwm fan ?
> > Maybe that a fake pwm interface is needed ?
> 
> Don't let yourself be fooled by the "pwm[1-n]" and "pwm[1_n]_enable"
> files names. These are valid for all fan control outputs, be they PWM
> or DC. As a matter of fact, "pwm[1-n]_mode" lets you advertise whether
> the controller is using PWM or DC.
> 
> All that really matters is that you use 0-255 as the pwm[1-n] range
> matching 0-100%.

Thank you.

Simon

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