linux-kernel - Re: Tachometer speed returned rather than absolute fan speed?

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Date:	Fri, 7 Mar 2014 15:47:08 +0000
From:	Laszlo Papp <lpapp@....org>
To:	Jean Delvare <jdelvare@...e.de>
Cc:	LKML <linux-kernel@...r.kernel.org>, lm-sensors@...sensors.org,
	Guenter Roeck <linux@...ck-us.net>
Subject: Re: Tachometer speed returned rather than absolute fan speed?

On Fri, Mar 7, 2014 at 3:37 PM, Jean Delvare <jdelvare@...e.de> wrote:
>> > I'm quite confused. While I admit that the term "tachometer speed" is
>> > awkward, the max6650 driver is reporting fan speeds in RPM as every
>> > other hwmon driver. So I really have no idea what you think is wrong.
>> > What did you think "tachometer speed" was, if not the fan speed? Does
>> > the max6650 driver not return correct fan speeds for you?

That is some strange behavior. If I do "echo 1 > pwm1_enable; echo 0 >
pwm1; cat fan1_input", I still see 30 for the connected fan, whereas I
can see it stopped. Is this an expected behavior? I would expect zero
as a user.

>> Better wording would have definitely helped in here. Fwiw, I asked
>> another kernel hacker person who also got confused telling me that he
>> would not know without reading the source code. I think that it is an
>> indication to improve the documentation. There might be better
>> alternatives than the one I am proposing, but at least that one clears
>> up that for me.
>
> I agree. I think I would just go with "measured fan speed in RPM", as
> tachometer is quite a technical term and the user doesn't need to know.
> Care to send a patch?

Hmm, yeah, perhaps. I can try to do that during the weekend.
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