linux-kernel - Re: [PATCH 2/3] dt-bindings: hwmon: Add bindings for Google Chromium EC HWMON

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Date:   Fri, 14 Apr 2017 07:48:15 -0500
From:   Rob Herring <robh@...nel.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Moritz Fischer <moritz.fischer@...us.com>,
        linux-hwmon@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Lee Jones <lee.jones@...aro.org>,
        Olof Johansson <olof@...om.net>,
        Jean Delvare <jdelvare@...e.com>,
        Mark Rutland <mark.rutland@....com>,
        Moritz Fischer <mdf@...nel.org>
Subject: Re: [PATCH 2/3] dt-bindings: hwmon: Add bindings for Google Chromium
 EC HWMON

On Thu, Apr 13, 2017 at 4:07 PM, Guenter Roeck <linux@...ck-us.net> wrote:
> On Thu, Apr 13, 2017 at 03:01:40PM -0500, Rob Herring wrote:
>> On Fri, Apr 07, 2017 at 03:00:09PM -0700, Moritz Fischer wrote:
>> > From: Moritz Fischer <mdf@...nel.org>
>> >
>> > Add bindings for the Chromium EC HWMON. The Chromium EC HWMON
>> > allows monitoring of temperature sensors and fans attached to the
>> > EC.
>> >
>> > Signed-off-by: Moritz Fischer <mdf@...nel.org>
>> > ---
>> >  .../devicetree/bindings/hwmon/cros-ec-hwmon.txt    | 25 ++++++++++++++++++++++
>> >  1 file changed, 25 insertions(+)
>> >  create mode 100644 Documentation/devicetree/bindings/hwmon/cros-ec-hwmon.txt
>> >
>> > diff --git a/Documentation/devicetree/bindings/hwmon/cros-ec-hwmon.txt b/Documentation/devicetree/bindings/hwmon/cros-ec-hwmon.txt
>> > new file mode 100644
>> > index 0000000..4c94869
>> > --- /dev/null
>> > +++ b/Documentation/devicetree/bindings/hwmon/cros-ec-hwmon.txt
>> > @@ -0,0 +1,25 @@
>> > +Chromium Embedded Controller EC temperature and fan control
>> > +-----------------------------------------------------------
>> > +
>> > +Google's Chromium EC HWMON is a hwmon implemented byimplemented by the Chromium EC
>> > +firmware attached to the Embedded Controller (EC) and controlled via a host-command
>> > +interface.
>> > +
>> > +An EC HWMON node should be only found as a sub-node of the EC node (see
>> > +Documentation/devicetree/bindings/mfd/cros-ec.txt).
>> > +
>> > +Required properties:
>> > +- compatible: Must contain "google,cros-ec-hwmon"
>> > +
>> > +Example:
>> > +   embedded-controller@1e {
>> > +           reg = <0x1e>;
>> > +           compatible = "google,cros-ec-i2c";
>> > +           interrupts = <0 IRQ_TYPE_LEVEL_LOW>;
>> > +           interrupt-parent = <&gpio0>;
>> > +
>> > +           hwmon {
>> > +                   compatible = "google,cros-ec-hwmon";
>>
>> This is sufficient for all devices? I don't see that DT provides
>> anything here other than instantiating a device, but the parent device
>> can just as easily do that.
>>
> The parent driver (drivers/mfd/cros_ec_i2c.c) calls cros_ec_register(),
> which uses uses of_platform_populate() to populate all sub-devices.
> There are various examples in the dts files (look for "google,cros-ec").
> Does it really make sense to start a second method for instantiating
> sub-devices ?

Okay, I suppose not. That wasn't clear from the example.

Rob