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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Wed, 10 Apr 2019 08:04:12 +0000
From:   Flavio Suligoi <f.suligoi@...m.it>
To:     Rob Herring <robh@...nel.org>
CC:     Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alessandro Zummo <a.zummo@...ertech.it>,
        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 Rob,

> On Mon, Apr 8, 2019 at 2:22 AM Flavio Suligoi <f.suligoi@...m.it> wrote:
> >
> > HI,
> >
> > > On 06/04/2019 01:07:13-0500, Rob Herring wrote:
> > > > On Wed, Apr 03, 2019 at 04:52:44PM +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
> > > > > +                            is available on the following
> devices:
> > > > > +                            - pcf2127 - pin used for alarm: INTn
> > > >
> > > > Boolean? If there's cases where which pin is selectable, then we'd
> need
> > > > this to take a value. Not sure how likely that is?
> > > >
> > >
> > > Indeed, there is at least the pcf85363 that has two possible pins for
> > > that interrupt. How would you select the pin then? a zero based index?
> a
> > > string?
> 
> I prefer an index.

Ok, so we can call this property as:

low-voltage-alarm

and we can select the pin using a zero-base index,
also for future developments.

> 
> > I think the string could be clearer for the final user and would give
> > more freedom for future changes.
> > For example, we can call this property, instead of "battery-low-alarm"
> or
> > "low-voltage-alarm", simply: "alarm-pin_1" and then the string argument
> > can describe the function used; for example:
> >
> > alarm-pin_1 = "backup-supply-low-voltage-alarm";
> > alarm-pin_2 = "......";
> 
> How many pins and functions then? And how does this relate to any
> interrupts?

If we use index, we don't use strings any more.