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

[Guenter Roeck]

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@xxxxxxxxxxxxxxxxxxxxx>
> > > > > Signed-off-by: Andrew Jeffery <andrew@xxxxxxxx>
> > > ---
> > > Hello,
> > >
> > > This is a rework of Timothy Pearson's original patch:
> > >
> > >      https://www.mail-archive.com/linux-hwmon@xxxxxxxxxxxxxxx/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.

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.

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