linux-kernel - Re: [PATCH v4 1/2] hwmon: w83627ehf driver cleanup

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Date:	Mon, 5 Jul 2010 13:59:00 +0200
From:	Jean Delvare <khali@...ux-fr.org>
To:	Guenter Roeck <guenter.roeck@...csson.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ethan Lawrence <e.law87@...oo.com>,
	Jim Cromie <jim.cromie@...il.com>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>,
	Iain <selsinork@...il.com>,
	"lm-sensors@...sensors.org" <lm-sensors@...sensors.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lars4910@...mail.com" <lars4910@...mail.com>,
	"birdie@...monline.ru" <birdie@...monline.ru>,
	"jadcock@....net" <jadcock@....net>,
	"binximeng@...il.com" <binximeng@...il.com>
Subject: Re: [PATCH v4 1/2] hwmon: w83627ehf driver cleanup

Hi Guenter,

On Sun, 4 Jul 2010 06:50:10 -0700, Guenter Roeck wrote:
> On Sun, Jul 04, 2010 at 07:24:42AM -0400, Jean Delvare wrote:
> > I'm skeptical. data->has_fan refers to fan inputs, not fan outputs.
> > There is no guarantee that pwm1 is mapped to fan1, etc., so you can't
> > use data->has_fan to discard fan outputs.
>
> Maybe, but they are treated as 1:1 for fan4 when creating the pwm files,
> and the pwm files for fan4 are not created if the matching bit isn't set.
> This applies to all chips supported by this driver. And for fan1..3, the
> mapping is supposed to be 1:1 per the driver documentation.

The driver documentation was written by ourselves, I wouldn't trust it ;)

Oh well, I hadn't noticed that sysfs file creation already assumes a
1:1 fan to pwm mapping. I am still unsure if it is correct, but it might
be good enough on practice, and your patch isn't changing it anyway, so
it's not the time to discuss it.

> I figured that it does not make sense to read the registers for a non-existing
> attribute file.

I agree that we want to skip register reads when possible (not that it
matters as much as when reading over slow SMBus though.) 

I have no further objections to your patch, so I'll apply it now. Then
I'll publish the patches and update the stand-alone driver, and we can
call for testers.

-- 
Jean Delvare
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