Re: [PATCH v2 1/2] dt-bindings: leds: Add leds-meter binding

[Akinobu Mita <akinobu.mita@gmail.com>]

2019年10月30日(水) 23:24 Rob Herring <robh@kernel.org>:
>
> On Sun, Oct 27, 2019 at 11:09:38PM +0900, Akinobu Mita wrote:
> > Add DT binding for generic LED level meter which consists of multiple LED
> > devices by different drivers.
>
> Do you have some pointers to actual h/w?

This doesn't require a specific hardware.
If there are more than two LEDs that can be described by devicetree,
it can be an LED level meter by bundling them up with this binding.

> > Cc: Rob Herring <robh+dt@kernel.org>
> > Cc: Mark Rutland <mark.rutland@arm.com>
> > Cc: Bjorn Andersson <bjorn@kryo.se>
> > Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
> > Cc: Jean-Jacques Hiblot <jjhiblot@ti.com>
> > Cc: Jacek Anaszewski <jacek.anaszewski@gmail.com>
> > Cc: Pavel Machek <pavel@ucw.cz>
> > Cc: Dan Murphy <dmurphy@ti.com>
> > Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
> > ---
> >  .../devicetree/bindings/leds/leds-meter.yaml       | 67 ++++++++++++++++++++++
> >  1 file changed, 67 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/leds/leds-meter.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/leds/leds-meter.yaml b/Documentation/devicetree/bindings/leds/leds-meter.yaml
> > new file mode 100644
> > index 0000000..b5fcd98
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/leds/leds-meter.yaml
> > @@ -0,0 +1,67 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/leds/leds-meter.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Generic LED level meter
> > +
> > +maintainers:
> > +  - Akinobu Mita <akinobu.mita@gmail.com>
> > +
> > +description:
> > +  Generic LED level meter consists of multiple LED devices by different drivers.
>
> Googling this, the only thing I see is audio level meters though those
> are all just a voltage level input, so it could be any source I guess.
>
> > +
> > +properties:
> > +  $nodename:
> > +    pattern: "^meter-leds(@.*)?"
> > +
> > +  compatible:
> > +    const: meter-leds
> > +
> > +  leds:
> > +    allOf:
> > +      - $ref: /schemas/types.yaml#/definitions/phandle-array
> > +    description: List of phandles to LED node that are members of a level meter.
> > +
> > +  brightness-weights:
> > +    allOf:
> > +      - $ref: /schemas/types.yaml#/definitions/uint32-array
> > +    description: |
> > +      By default, the brightness of the LED level meter is proportional to the
> > +      number of actual LEDs that are turned on.  We can optionally specify
> > +      the contribution ratio for each LED within a level meter by this
> > +      property.  The example below shows how to setup an exponential
> > +      relationship between the number of LEDs turned on and the brightness of
> > +      meter-leds.
>
> This seems oddly named if this is a bar graph. Yes, more LEDs on is
> brighter, but it's really a piecewise linear graph you want.

OK.  I'll rewrite the description.

> Each LED could have variable brightness, so you could also ramp the
> brightness for an individual LED.

For now, each LED is set to 0 or max brightness.  Maybe we should
set middle brightness value for an LED on the border line.