Subject: [PATCH V4 9/9] pwm_bl: Add mandatory backlight enable regulator

From: [email-masked] (Stephen Warren)
Date: Wed, 20 Mar 2013 12:00:10 -0600

On 03/19/2013 12:59 PM, Andrew Chew wrote:
> Many backlights need to be explicitly enabled.  Typically, this is done
> with a GPIO.  For flexibility, we generalize the enable mechanism to a
> regulator.
> 
> If an enable regulator is not needed, then a dummy regulator can be given
> to the backlight driver.  If a GPIO is used to enable the backlight,
> then a fixed regulator can be instantiated to control the GPIO.
> 
> The backlight enable regulator can be specified in the device tree node
> for the backlight, or can be done with legacy board setup code in the
> usual way.

> diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> index 1e4fc72..7e2e089 100644
> --- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> +++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
> @@ -10,6 +10,11 @@ Required properties:
>        last value in the array represents a 100% duty cycle (brightest).
>    - default-brightness-level: the default brightness level (index into the
>        array defined by the "brightness-levels" property)
> +  - enable-supply: A phandle to the regulator device tree node. This
> +      regulator will be turned on and off as the pwm is enabled and disabled.
> +      Many backlights are enabled via a GPIO. In this case, we instantiate
> +      a fixed regulator and give that to enable-supply. If a regulator
> +      is not needed, then provide a dummy fixed regulator.

"enable" doesn't seem like the right name here; if this really is an
"enable" input, then it's not a regulator. If you're calling it "enable"
because the regulator is usually controlled by a GPIO that enables it,
then what you really have is a regulator that provides power to the
backlight, and the method that you enable that regulator is irrelevant.

Put another way, wouldn't "power" be a better name, thus making the
property "power-supply"? Although that property name migth be considered
to have some negative correlation with other concepts, so if people
object to that, perhaps e.g. "vdd-supply"?