linux-kernel - RE: [PATCH 1/2] dt-bindings: rtc: add battery-low-hw-alarm property

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Message-ID: <b45fc9a86a0d4126ad6d8dda9c883043@asem.it>
Date:   Wed, 3 Apr 2019 15:06:17 +0000
From:   Flavio Suligoi <f.suligoi@...m.it>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
CC:     Alessandro Zummo <a.zummo@...ertech.it>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "linux-rtc@...r.kernel.org" <linux-rtc@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/2] dt-bindings: rtc: add battery-low-hw-alarm property

Hi Alexandre,

> Hi,
> 
> On 03/04/2019 16:52:44+0200, Flavio Suligoi wrote:
> > Some RTC devices have a battery-low automatic detection circuit.
> > The battery-low event is usually reported with:
> >
> > - a bit change in a RTC status register
> > - a hw signaling (generally using an interrupt generation), changing
> >   the hw level of a specific pin;
> >
> > The new property "battery-low-hw-alarm" enable the RTC to generate the
> > hw signaling in case of battery-low event.
> >
> > Signed-off-by: Flavio Suligoi <f.suligoi@...m.it>
> > ---
> >  Documentation/devicetree/bindings/rtc/rtc.txt | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/rtc/rtc.txt
> b/Documentation/devicetree/bindings/rtc/rtc.txt
> > index a97fc6a..f93a44d 100644
> > --- a/Documentation/devicetree/bindings/rtc/rtc.txt
> > +++ b/Documentation/devicetree/bindings/rtc/rtc.txt
> > @@ -31,6 +31,9 @@ below.
> >                              expressed in femto Farad (fF).
> >                              The default value shall be listed (if
> optional),
> >                              and likewise all valid values.
> > +- battery-low-hw-alarm :    Enable the "battery-low" output pin. This
> function
> 
> I would name that voltage-low-alarm as not all the secondary voltages
> are batteries.

You have right. So we can also name the property a: "voltage-low-hw-alarm". 
I prefer to have the word "hw" in the property name, since the "sw" voltage
low alarm is already present is some RTC drivers. 
In this way, with the word "hw", is more clear that we are speaking about
an hw pin signaling.

> 
> > +                            is available on the following devices:
> > +                            - pcf2127 - pin used for alarm: INTn
> >
> >  Trivial RTCs
> >  ------------
> > --
> > 2.7.4
> >
> 
> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com


Thanks,

Flavio Suligoi