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Message-ID: <20200622142215.biy2g6sd44czky4u@holly.lan>
Date: Mon, 22 Jun 2020 15:22:15 +0100
From: Daniel Thompson <daniel.thompson@...aro.org>
To: Rob Herring <robh@...nel.org>
Cc: devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
linux-kernel@...r.kernel.org, Lee Jones <lee.jones@...aro.org>,
Jingoo Han <jingoohan1@...il.com>
Subject: Re: [PATCH] dt-bindings: backlight: Convert common backlight
bindings to DT schema
On Thu, Jun 18, 2020 at 04:44:13PM -0600, Rob Herring wrote:
> Convert the common GPIO, LED, and PWM backlight bindings to DT schema
> format.
>
> Given there's only 2 common properties and the descriptions are slightly
> different, I opted to not create a common backlight schema.
>
> Cc: Lee Jones <lee.jones@...aro.org>
> Cc: Daniel Thompson <daniel.thompson@...aro.org>
> Cc: Jingoo Han <jingoohan1@...il.com>
> Signed-off-by: Rob Herring <robh@...nel.org>
...
> diff --git a/Documentation/devicetree/bindings/leds/backlight/led-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/led-backlight.yaml
> new file mode 100644
> index 000000000000..ae50945d2798
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/led-backlight.yaml
> @@ -0,0 +1,58 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/led-backlight.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: led-backlight bindings
> +
> +maintainers:
> + - Lee Jones <lee.jones@...aro.org>
> + - Daniel Thompson <daniel.thompson@...aro.org>
> + - Jingoo Han <jingoohan1@...il.com>
> +
> +description:
> + This binding is used to describe a basic backlight device made of LEDs. It
> + can also be used to describe a backlight device controlled by the output of
> + a LED driver.
> +
> +properties:
> + compatible:
> + const: led-backlight
> +
> + leds:
> + description: A list of LED nodes
> + $ref: /schemas/types.yaml#/definitions/phandle-array
> +
> + brightness-levels:
> + description: Array of distinct brightness levels. The levels must be
> + in the range accepted by the underlying LED devices. This is used
> + to translate a backlight brightness level into a LED brightness level.
> + If it is not provided, the identity mapping is used.
> + $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> + default-brightness-level:
> + description: The default brightness level (index into the array defined
> + by the "brightness-levels" property).
> + $ref: /schemas/types.yaml#/definitions/uint32
> +
> +dependencies:
> + default-brightness-level: [brightness-levels]
I don't think there is a dependency here. default-brightness-level still
makes sense with there is no mapping table present.
Based on Sam's feedback perhaps adding ("if one is provided") to the
parenthetic text.
> diff --git a/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml
> new file mode 100644
> index 000000000000..7e1f109a38a4
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/leds/backlight/pwm-backlight.yaml
> @@ -0,0 +1,98 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/leds/backlight/pwm-backlight.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: pwm-backlight bindings
> +
> +maintainers:
> + - Lee Jones <lee.jones@...aro.org>
> + - Daniel Thompson <daniel.thompson@...aro.org>
> + - Jingoo Han <jingoohan1@...il.com>
> +
> +properties:
> + compatible:
> + const: pwm-backlight
> +
> + pwms:
> + maxItems: 1
> +
> + pwm-names: true
> +
> + power-supply:
> + description: regulator for supply voltage
> +
> + enable-gpios:
> + description: Contains a single GPIO specifier for the GPIO which enables
> + and disables the backlight
> + maxItems: 1
> +
> + post-pwm-on-delay-ms:
> + description: Delay in ms between setting an initial (non-zero) PWM and
> + enabling the backlight using GPIO.
> +
> + pwm-off-delay-ms:
> + description: Delay in ms between disabling the backlight using GPIO
> + and setting PWM value to 0.
> +
> + brightness-levels:
> + description: Array of distinct brightness levels. Typically these are
> + in the range from 0 to 255, but any range starting at 0 will do. The
> + actual brightness level (PWM duty cycle) will be interpolated from
> + these values. 0 means a 0% duty cycle (darkest/off), while the last
> + value in the array represents a 100% duty cycle (brightest).
> + $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> + default-brightness-level:
> + description: The default brightness level (index into the array defined
> + by the "brightness-levels" property).
> + $ref: /schemas/types.yaml#/definitions/uint32
> +
> + num-interpolated-steps:
> + description: Number of interpolated steps between each value of brightness-levels
> + table. This way a high resolution pwm duty cycle can be used without
> + having to list out every possible value in the brightness-level array.
> + $ref: /schemas/types.yaml#/definitions/uint32
> +
> +dependencies:
> + default-brightness-level: [brightness-levels]
> + num-interpolated-steps: [brightness-levels]
Just for the record, these dependencies are OK. Iit isn't really a good
idea to map 1:1 to a PWM since we end up with a gazillion
indistinguishable levels so the bindings (and the driver) to not allow
such a mode.
Daniel.
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