linux-kernel - Re: [PATCH 1/2] dt-bindings: trivial: add ti,lm3630a binding

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Message-ID: <CAL_Jsq+-AZFf==911Pmf_ObUk+3VQgC+2+BvQ9q8LyQ_v=FdOA@mail.gmail.com>
Date:   Fri, 30 Nov 2018 08:13:04 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Brian Masney <masneyb@...tation.org>
Cc:     Daniel Thompson <daniel.thompson@...aro.org>,
        Lee Jones <lee.jones@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-fbdev@...r.kernel.org, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jonathan Marek <jonathan@...ek.ca>,
        Craig Tatlor <ctatlor97@...il.com>, Dan Murphy <dmurphy@...com>
Subject: Re: [PATCH 1/2] dt-bindings: trivial: add ti,lm3630a binding

+Dan M

On Fri, Nov 30, 2018 at 7:59 AM Brian Masney <masneyb@...tation.org> wrote:
>
> On Tue, Nov 27, 2018 at 10:56:42AM +0000, Daniel Thompson wrote:
> > On Sat, Nov 24, 2018 at 09:17:02AM -0500, Brian Masney wrote:
> > > Add a trivial binding for the Texas Instruments LM3630A Backlight Chip.

How does this chip relate to ones Dan has been working on?

> >
> > It's quite unusual for a backlight device to have a trivial binding.
> >
> > The driver supports fairly extensive parametrization via struct
> > lm3530a_platform_data. It is really the case that none of these
> > properties should ever be set via DT?
>
> Hi Daniel,
>
> I initially assumed that we would let user space configure these values
> once the system has booted, but you are right that these should be
> available in device tree.
>
> The driver has two different LED banks that can be configured
> independently.

That is usually represented with child nodes which makes this anything
but trivial. Plus, given that we have bindings for LEDs/backlights, no
LED/backlight controller is a trivial device.

> How do you feel about having a single property in
> device tree populate the initial values for both banks? I propose that
> we could use the property default-brightness-level for leda_init_brt
> and ledb_init_brt in struct lm3630a_platform_data. The max-brightness
> property can populate leda_max_brt and ledb_max_brt.
>
> I need to look at other bindings this weekend to see if there are any
> standard properties that I can use for leda_ctrl/ledb_ctrl, pwm_ctrl,
> and pwm_period.
>
> Brian
>