Re: [PATCH v2] hwmon: (sht3x) add devicetree support

[Rob Herring <robh@kernel.org>]

On Mon, Oct 15, 2018 at 2:54 PM Guenter Roeck <linux@roeck-us.net> wrote:
>
> On Mon, Oct 15, 2018 at 07:55:58AM +0200, Wojciech Sleńska wrote:
> > pt., 12 paź 2018 o 22:28 Rob Herring <robh@kernel.org> napisał(a):
> > >
> > > On Fri, Oct 05, 2018 at 07:38:35AM +0200, Wojciech Slenska wrote:
> > >
> > > Commit msg?
> > >
> > > > Signed-off-by: Wojciech Slenska <wojciech.slenska@gmail.com>
> > > > ---
> > > >  Documentation/devicetree/bindings/hwmon/sht3x.txt | 16 +++++++++++++
> > >
> > > Please split bindings to separate patch.
> >
> > I will do this.
> >
> > >
> > > >  drivers/hwmon/sht3x.c                             | 28 ++++++++++++++++++++---
> > > >  2 files changed, 41 insertions(+), 3 deletions(-)
> > > >  create mode 100644 Documentation/devicetree/bindings/hwmon/sht3x.txt
> > > >
> > > > diff --git a/Documentation/devicetree/bindings/hwmon/sht3x.txt b/Documentation/devicetree/bindings/hwmon/sht3x.txt
> > > > new file mode 100644
> > > > index 0000000..80b117e
> > > > --- /dev/null
> > > > +++ b/Documentation/devicetree/bindings/hwmon/sht3x.txt
> > > > @@ -0,0 +1,16 @@
> > > > +Sensirion SHT3x Humidity and Temperature Sensor
> > > > +
> > > > +Required node properties:
> > > > +- compatible: "sensirion,sht3x" or "sensirion,sts3x"
> > > > +- reg: I2C bus address of the device
> > > > +
> > > > +Optional properties:
> > > > +- sensirion,blocking-io: enable blocking mode on i2c
> > >
> > > This is not a h/w parameter and shouldn't be in DT.
> > >
> > > > +- sensirion,no-high-precision: disable high accuracy
> > >
> > > Maybe this one is okay, but couldn't the user want to set this? If so,
> > > then it should be a sysfs attr.
> >
> > Those two parameters have been just moved from
> > linux/include/linux/platform_data/sht3x.h
> > Currently, those two parameters can be set in board file, so for me
> > was natural to move it to dts.
> > Of course, I can remove it from dts completely.
> >
>
> I wonder if there is an authoritative document explaining the current policy
> in respect to devicetree properties.

No. In the end it is often a judgement call.

> Sometimes I hear that platform
> configuration parameters are now permitted, sometimes I hear that we are
> back to hardware description only.

Yes, configuration is permitted, but there are some constraints. The
questions I ask are is it OS specific or specific to current
implementation of an OS, who or what decides what the setting is? The
last question results in lots of things dropped in favor of a sysfs
control.

Rob