Re: [PATCH v2] ARM: dts: vfxxx: Add iio_hwmon node for ADC temperature channel

[Guenter Roeck]

On 02/14/2016 08:42 PM, maitysanchayan@xxxxxxxxx wrote:
> Hello Shawn,
>
> On 16-02-14 16:33:49, Shawn Guo wrote:
> > On Fri, Feb 12, 2016 at 05:53:00PM +0530, Sanchayan Maity wrote:
> > > Add iio_hwmon node to expose the temperature channel on Vybrid as
> > > hardware monitor device using the iio_hwmon driver.
> > >
> > > Signed-off-by: Sanchayan Maity <maitysanchayan@xxxxxxxxx>
> > > ---
> > >
> > > Hello,
> > >
> > > The first version of the patch was send quite a while ago.
> > > https://lkml.org/lkml/2015/9/16/932
> > >
> > > Shawn you had requested that hyphen rather than underscore should
> > > be used in node name. I looked into that.
> > >
> > > The iio_hwmon driver calls hwmon_device register_with_groups inside
> > > hwmon.c and this
> > > http://lxr.free-electrons.com/source/drivers/hwmon/hwmon.c#L103
> > >
> > > does not allow hyphen in hwmon name attribute. I was not aware of
> > > this but while trying to test the change, the device probe failed
> > > with EINVAL. I think we should stick to the existing use of the
> > > bindings or we need to change the hwmon code as well along with the
> > > existing device tree files and binding documentation.
> >
> > I disagree.
> >
> > If hyphen is invalid to be part of hwmon name attribute, the following
> > code in iio_hwmon_probe() is plain wrong, because hyphen is very valid
> > to be part of node names in device tree.
> >
> >          if (dev->of_node && dev->of_node->name)
> >                  name = dev->of_node->name;
>
> @Shawn
> I agree with what you state here, however as you can see the hwmon_device_
> register_with_groups does check for hypen with strpbrk and returns EINVAL.
> Changing to hyphen instead of currently present underscore in iio_hwmon
> node name causes probe failure.
>
> If the node name needs to have hyphen, then the check for hyphen as an invalid
> character in hwmon name attribute needs to be changed. I am CC'ing the hwmon
> subsystem maintainers Jean Delvare ands Guenter Roeck as well as hwmon list to
> check.
>
> @Jean & Guenter
> Can you please comment if the change to hwmon_device_register_with_groups
> to accept hyphen as a valid character in hwmon name attribute will be acceptable?

User space would not like the '-' and get confused.

We'll have to change the above code and replace '-' with '_' in the name if/when
it is seen. Sorry, I didn't realize the problem when I wrote that code.

Guenter

> Sorry if this is sudden andfor bringing you late into the discussion Jean and
> Guenter.
>
> Thanks & Regards,
> Sanchayan.
>
> > Shawn
> >
> > > Changes since v1:
> > > 1. Expose ADC1 temperature channel as well
> > > 2. Move the entry outside of the aips1 bus node
> > >
> > > Best Regards,
> > > Sanchayan Maity.
> > > ---
> > >   arch/arm/boot/dts/vfxxx.dtsi | 5 +++++
> > >   1 file changed, 5 insertions(+)
> > >
> > > diff --git a/arch/arm/boot/dts/vfxxx.dtsi b/arch/arm/boot/dts/vfxxx.dtsi
> > > index a5f07e3..8ed8e47 100644
> > > --- a/arch/arm/boot/dts/vfxxx.dtsi
> > > +++ b/arch/arm/boot/dts/vfxxx.dtsi
> > > @@ -673,5 +673,10 @@
> > >   				status = "disabled";
> > >   			};
> > >   		};
> > > +
> > > +		iio_hwmon {
> > > +			compatible = "iio-hwmon";
> > > +			io-channels = <&adc0 16>, <&adc1 16>;
> > > +		};
> > >   	};
> > >   };
> > > --
> > > 2.7.1