On Mon, Jun 29, 2020 at 09:18:47PM +0200, Sam Ravnborg wrote:
On Mon, Jun 29, 2020 at 11:57:37AM -0600, Rob Herring wrote:
On Mon, Jun 22, 2020 at 10:57 AM Daniel Thompson daniel.thompson@linaro.org wrote:
On Fri, Jun 19, 2020 at 11:53:41PM +0200, Sam Ravnborg wrote:
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@linaro.org
- Daniel Thompson daniel.thompson@linaro.org
- Jingoo Han jingoohan1@gmail.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. Theactual brightness level (PWM duty cycle) will be interpolated fromthese values. 0 means a 0% duty cycle (darkest/off), while the lastvalue 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
Same comment as before...
Sorry the "ditto" meant I didn't thing about PWM as much as I should have.
The situation for PWM is a little different to LED. That's mostly because we decided not to clutter the LED code with "num-interpolated-steps".
The PWM code implements the default-brightness-level as an index into the brightness array *after* it has been expanded using interpolation. In other words today Linux treats the default-brightness-level more like[1].
description: The default brightness level. When num-interpolated-steps is not set this is simply an index into the array defined by the "brightness-levels" property. If num-interpolated-steps is set the brightness array will be expanded by interpolation before we index to get a default level.This is the best I have come up with so far... but I concede it still lacks elegance.
Happy to add this or whatever folks want if there's agreement, but I don't want to get bogged down on re-reviewing and re-writing the binding on what is just a conversion. There's a mountain of bindings to convert.
The original explanation is ok, as pointed out by Daniel. So I suggest moving forward with that and then others can improve the descriptions later as necessary.
That's fine for me to. It would be clearer in version history (improving definitions during a conversion hides them when mining the changelog).
Daniel.