linux-kernel - Re: [lm-sensors] [PATCH] hwmon: pwm-fan: Add pwm-fan driver

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Date:	Thu, 10 Jul 2014 09:17:13 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Kamil Debski <k.debski@...sung.com>
CC:	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	lm-sensors@...sensors.org, Tomasz Figa <t.figa@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [lm-sensors] [PATCH] hwmon: pwm-fan: Add pwm-fan driver

Hi Kamil,

On 07/10/2014 08:17 AM, Kamil Debski wrote:
>
>>
>>> +	}
>>> +
>>> +	dev_set_drvdata(&pdev->dev, ctx);
>>> +	platform_set_drvdata(pdev, ctx);
>>> +
>>> +	/* Set duty cycle to maximum allowed */
>>> +	ctx->duty_cycle = ctx->pwm->period - 1;
>>> +	ctx->pwm_value = MAX_PWM;
>>> +	pwm_config(ctx->pwm, ctx->duty_cycle, ctx->pwm->period);
>
> Guenter, I have a question regarding this. I see that gpio-fan reads
> the state of gpios and uses this as the initial setting.
> Led-pwm on init sets the brightness to LED_OFF.
>
> What should be the default state after init? Should the fan be off or
> at full power? I am thinking about adding an optional node to device
> tree that could be used to set this. But the question remains - what
> should be the default setting?
>

Trick question ... I can not really answer it. you can try the devicetree
option, but be prepared to have it rejected - the usual argument is that
dt shall only describe the HW but not its configuration.

Ultimately, either way is fine with me.

Guenter

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