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Subject[PATCH] pwm-backlight: add "max-brightness" property
Date
Specifying each individual brightness value via the "brightness-levels"
property can be a pain if we want to use a large continuous range of
brightness values. Add the property "max-brightness", which can be
given in place of "brightness-levels", that specifies that all values
between 0 and the given value can be used.

Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
---
.../bindings/video/backlight/pwm-backlight.txt | 22 +++++++++---
drivers/video/backlight/pwm_bl.c | 39 +++++++++++++---------
2 files changed, 42 insertions(+), 19 deletions(-)

diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
index 1e4fc72..856dfc9 100644
--- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
@@ -3,15 +3,21 @@ pwm-backlight bindings
Required properties:
- compatible: "pwm-backlight"
- pwms: OF device-tree PWM specification (see PWM binding[0])
+ - one of "brightness-levels" or "max-brightness", described below
+ - default-brightness-level: the default brightness level (index into the array
+ defined by the "brightness-levels" property or a value between 0 and
+ "max-brightness")
+
+Optional properties:
- brightness-levels: 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).
- - default-brightness-level: the default brightness level (index into the
- array defined by the "brightness-levels" property)
-
-Optional properties:
+ - max-brightness: Instead of specifying a complete set of brightness
+ levels, a single maximum brightness value may be given. This indicates
+ that all integers between 0 and max-brightness are valid brightness
+ values.
- pwm-names: a list of names for the PWM devices specified in the
"pwms" property (see PWM binding[0])

@@ -26,3 +32,11 @@ Example:
brightness-levels = <0 4 8 16 32 64 128 255>;
default-brightness-level = <6>;
};
+or:
+ backlight {
+ compatible = "pwm-backlight";
+ pwms = <&pwm 0 1000000 0>;
+
+ max-brightness = <1024>;
+ default-brightness-level = <700>;
+ };
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index 1fea627..92973b1 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c
@@ -98,7 +98,6 @@ static int pwm_backlight_parse_dt(struct device *dev,
struct platform_pwm_backlight_data *data)
{
struct device_node *node = dev->of_node;
- struct property *prop;
int length;
u32 value;
int ret;
@@ -108,34 +107,44 @@ static int pwm_backlight_parse_dt(struct device *dev,

memset(data, 0, sizeof(*data));

- /* determine the number of brightness levels */
- prop = of_find_property(node, "brightness-levels", &length);
- if (!prop)
- return -EINVAL;
+ if (of_find_property(node, "brightness-levels", &length)) {
+ data->max_brightness = length / sizeof(u32);

- data->max_brightness = length / sizeof(u32);
+ /* read brightness levels from DT property */
+ if (data->max_brightness > 0) {
+ size_t size = sizeof(*data->levels) *
+ data->max_brightness;

- /* read brightness levels from DT property */
- if (data->max_brightness > 0) {
- size_t size = sizeof(*data->levels) * data->max_brightness;
-
- data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
- if (!data->levels)
- return -ENOMEM;
+ data->levels = devm_kzalloc(dev, size, GFP_KERNEL);
+ if (!data->levels)
+ return -ENOMEM;

- ret = of_property_read_u32_array(node, "brightness-levels",
+ ret = of_property_read_u32_array(node,
+ "brightness-levels",
data->levels,
data->max_brightness);
+ if (ret < 0)
+ return ret;
+
+ data->max_brightness--;
+ }
+ } else {
+ ret = of_property_read_u32(node, "max-brightness",
+ &value);
if (ret < 0)
return ret;

+ /* brightness values are 0 to max-brightness */
+ data->max_brightness = value;
+ }
+
+ if (data->max_brightness > 0) {
ret = of_property_read_u32(node, "default-brightness-level",
&value);
if (ret < 0)
return ret;

data->dft_brightness = value;
- data->max_brightness--;
}

/*
--
1.8.3


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