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

On Wed, Mar 20, 2013 at 12:00:10PM -0600, Stephen Warren wrote:

On 03/19/2013 12:59 PM, Andrew Chew wrote:

quoted

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.

quoted

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"?

"power" sounds like a reasonable name to me.

Thierry
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