linux-kernel - Re: [PATCH v3] hwmon: Add support for MAX31785 intelligent fan controller

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Message-ID: <1496969522.23335.5.camel@aj.id.au>
Date:   Fri, 09 Jun 2017 10:22:02 +0930
From:   Andrew Jeffery <andrew@...id.au>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-hwmon@...r.kernel.org, jdelvare@...e.com, corbet@....net,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        joel@....id.au, msbarth@...ux.vnet.ibm.com,
        tpearson@...torengineering.com, openbmc@...ts.ozlabs.org
Subject: Re: [PATCH v3] hwmon: Add support for MAX31785 intelligent fan
 controller

On Thu, 2017-06-08 at 05:37 -0700, Guenter Roeck wrote:
> On 06/08/2017 12:53 AM, Andrew Jeffery wrote:
> > On Wed, 2017-06-07 at 08:55 -0700, Guenter Roeck wrote:
> > > On Tue, Jun 06, 2017 at 04:32:30PM +0930, Andrew Jeffery wrote:
> > > > Add a basic driver for the MAX31785, focusing on the fan control
> > > > features but ignoring the temperature and voltage monitoring
> > > > features of the device.
> > > > 
> > > > This driver supports all fan control modes and tachometer / PWM
> > > > readback where applicable.
> > > > 
> > > > > > Signed-off-by: Timothy Pearson <tpearson@...torengineering.com>
> > > > > > Signed-off-by: Andrew Jeffery <andrew@...id.au>
> > > > 
> > > > ---
> > > > Hello,
> > > > 
> > > > This is a rework of Timothy Pearson's original patch:
> > > > 
> > > >      https://www.mail-archive.com/linux-hwmon@vger.kernel.org/msg00868.html
> > > > 
> > > > I've labelled it as v3 to differentiate from Timothy's postings.
> > > > 
> > > > The original thread had some discussion about the MAX31785 being a PMBus device
> > > > and that it should thus be a PMBus driver. The implementation still makes use
> > > 
> > > After thinking about it, that is what it should be. If I accept it as non-PMBus
> > > driver, it will be all but impossible to convert it to a PMBus driver later on,
> > > and that just doesn't make any sense.
> > 
> > Hopefully not being too ignorant here, but can you expand on why it
> > would be all but impossible to convert?
> > 
> 
> I've got a lot of noise recently just for converting a driver from the old to the
> new API (which changes the attribute location). Changing the driver from non-PMBus
> to PMBus would very quite likely change some attributes as well.

Okay.

> 
> Besides that, I think it is a bad idea to bypass an infrastructure just because
> it may require a few tweaks. That generates a bad precedent, and people _would_
> use that to argue that the next PMBus chip driver should not use the infrastructure
> either.

I understand not wanting to set a precedent. Thanks for your response.

Andrew

> 
> Guenter
> 
> > > 
> > > With no one interested in writing that driver, I'll try to give it some more
> > > priority myself. I do have an evaluation board somewhere, which should help.
> > > 
> > > Note that the second fan reading should be implemented as just that, not with
> > > a non-standard attribute.
> > 
> > Agreed.
> > 
> > Andrew
> > 
> 
> 
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