linux-kernel - Re: [PATCH v3 1/5] dt-bindings: leds: Add pattern initialization from Device Tree

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]

Message-ID: <CAJKOXPd_icrPUQJhbcHkovQ7DFYM5mVZmXG_qbHv3KKjxVEdbg@mail.gmail.com>
Date:   Tue, 18 Dec 2018 10:06:14 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Pavel Machek <pavel@....cz>,
        Mark Rutland <mark.rutland@....com>,
        Baolin Wang <baolin.wang@...aro.org>,
        linux-leds@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/5] dt-bindings: leds: Add pattern initialization from
 Device Tree

On Mon, 17 Dec 2018 at 23:40, Rob Herring <robh@...nel.org> wrote:
>
> On Wed, Dec 12, 2018 at 12:16:42PM +0100, Krzysztof Kozlowski wrote:
> > Document new linux,trigger-pattern property for initialization of LED
> > pattern trigger.
> >
> > Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>
> > ---
> >  Documentation/devicetree/bindings/leds/common.txt | 36 +++++++++++++++++++++++
> >  1 file changed, 36 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/leds/common.txt b/Documentation/devicetree/bindings/leds/common.txt
> > index aa1399814a2a..3daccd4ea8a3 100644
> > --- a/Documentation/devicetree/bindings/leds/common.txt
> > +++ b/Documentation/devicetree/bindings/leds/common.txt
> > @@ -37,6 +37,42 @@ Optional properties for child nodes:
> >       "ide-disk" - LED indicates IDE disk activity (deprecated),
> >                    in new implementations use "disk-activity"
> >       "timer" - LED flashes at a fixed, configurable rate
> > +     "pattern" - LED alters the brightness for the specified duration with one
> > +                 software timer (requires "led-pattern" property)
> > +
> > +- led-pattern : String with default pattern for certain triggers. Each trigger
> > +                may parse this string differently:
> > +                - one-shot : two numbers specifying delay on and delay off,
> > +                - timer : two numbers specifying delay on and delay off,
>
> I misunderstood that these triggers applied to this. Is there any point
> to supporting these modes?

I am not sure whether I explained this clearly enough, so let me be
more specific. The "led-pattern" is a string with pattern which will
be interpreted differently, based on LED trigger. One-shot and timer
triggers expect two numbers. Pattern trigger expects full pattern.

> Aren't they just a subset or simplification
> of a pattern?

Yes, they are.

>
> Can we control the timer frequency from DT? The pattern could address
> that limitation.

No, currently we cannot. This patch with pattern solves that issue.

>
> > +                - pattern : The pattern is given by a series of tuples, of
>
> Don't you need one-shot vs. repeat modes for patterns too?

Repeat mode is defined by trigger. One-shot is one time. Timer and
patter triggers are repeating.

>
> I could imagine you'd want a pattern for any trigger.

In general I think that only these three triggers require such
initialization through pattern. Other triggers - like heartbeat or
activity - have they own bindings (or do not need any).

Following Pavel's suggestion, I could convert it to array of integers
which still should be suitable for these and any future triggers
operating on numbers.

Best regards,
Krzysztof