Re: [lm-sensors] [PATCH] hwmon: (max6650) Add support for gpiodef

[Guenter Roeck <linux@roeck-us.net>]

On Tue, Nov 19, 2013 at 08:54:38AM -0800, Guenter Roeck wrote:
> On Tue, Nov 19, 2013 at 04:42:49PM +0000, Laszlo Papp wrote:
> > On Fri, Nov 15, 2013 at 7:52 PM, Marcus Folkesson
> > <marcus.folkesson@gmail.com> wrote:
> > >
> > >> This is just one use case of those, you could also use it for
> > >> non-generic gpio functionality, like alarm, "full-on", internal clock,
> > >> external clock, etc. I believe it is always a bit tricky with MFD. I
> > >> personally prefer to put it into the chip driver because this is not
> > >> clearly a generic gpio interface here, and I need to drive it
> > >> dynamically.
> > >
> > > I agree.
> > >
> > > I think the solution with expose the "GPIOs" in sysfs is the right way to
> > > go.
> > > The chip-function is of a dynamic nature and should therefor not be set in
> > > platform data / devicetree.
> > >
> > > As mentioned before, GPIOs should use the gpio subsystem whenever possible,
> > > but the the gpio-functionality is just a subset of
> > > functions these pins may be set to.
> > >
> > > Also, the I think the *real* reason why the entries is called "gpio" is that
> > > it is so the registers are are mentioned in the datasheet.
> > > Everyone that is working with the device will know what it is all about.
> > > I see it more as an register expose than a gpio interface...
> > >
> > > I agree that the entries does not really fit here. But they does not fit
> > > better elsewhere either.
> > > And I don't think they fit worse than the alarm-entries that is already in
> > > mainline.
> > >
> > > Anyway, I think the documentation file should mention what function each
> > > valid value represent.
> > 
> > Yes, makes sense to make the documentation more comprehensive. Thanks.
> > 
> > Any other issues from anyone before submitting a polished version?
> > 
> You'll have to get feedback from Jean. I won't accept the patch.
> 
To add to this: The datasheet clearly states that the pins are GPIO pins,
three of which can be configured as ALERT output, ALL_ON input, or clock
input/output. GPIO pins should be made available to the kernel through
the GPIO subsystem; any clock configuration should be configured through the
clock subsystem if needed. The pin configuration as ALERT output/ALL_ON
input/clock is clearly board specific and should thus be provided as
platform data and/or devicetree data if needed.

The existing GPIO alarm attributes should be removed. The pin values should be
reported as GPIO pin values instead.

Guenter