[PATCH 4/4] pwm_backlight: Add support for the whole range of the PWM in DT mode
From: Peter Ujfalusi <hidden>
Date: 2013-01-22 13:40:30
Also in:
linux-devicetree, lkml
Subsystem:
backlight class/subsystem, framebuffer layer, open firmware and flattened device tree bindings, the rest · Maintainers:
Lee Jones, Daniel Thompson, Jingoo Han, Helge Deller, Rob Herring, Krzysztof Kozlowski, Conor Dooley, Linus Torvalds
When booting with DT make it possible to use the whole range of the PWM when controlling the backlight in a same way it is possible when the kernel is booted in non DT mode. A new property "max-brightness-level" can be used to specify the maximum value the PWM can handle (time slots). DTS files can use either the "brightness-levels" or the "max-brightness-level" to configure the PWM. In case both of these properties exist the driver will prefer the "brightness-levels" over the "max-brightness-level". Signed-off-by: Peter Ujfalusi <redacted> --- .../bindings/video/backlight/pwm-backlight.txt | 12 +++++++++-- drivers/video/backlight/pwm_bl.c | 24 ++++++++++++++-------- 2 files changed, 25 insertions(+), 11 deletions(-)
diff --git a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
index 1e4fc72..517924b 100644
--- a/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt
+++ b/Documentation/devicetree/bindings/video/backlight/pwm-backlight.txt@@ -3,13 +3,21 @@ pwm-backlight bindings Required properties: - compatible: "pwm-backlight" - pwms: OF device-tree PWM specification (see PWM binding[0]) + + Brightness range can be configured with either "brightness-levels" or with + "max-brightness-level". - 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) + - max-brightness-level: The maximum brightness level the PWM supports. When + the brightness is specified using this property the whole range from 0 to + "max-brightness-level" will be available to configure. + - default-brightness-level: the default brightness level. With + "brightness-levels" it is an index into the array defined by the + "brightness-levels" property. When it is used with "max-brightness-level" + it is the value in the range from 0 to "max-brightness-level" Optional properties: - pwm-names: a list of names for the PWM devices specified in the
diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c
index df2d115..c0e4bc7 100644
--- a/drivers/video/backlight/pwm_bl.c
+++ b/drivers/video/backlight/pwm_bl.c@@ -111,10 +111,17 @@ static int pwm_backlight_parse_dt(struct device *dev, /* determine the number of brightness levels */ prop = of_find_property(node, "brightness-levels", &num_levels); - if (!prop) - return -EINVAL; + if (!prop) { + /* Levels not provided, look for the maximum property */ + ret = of_property_read_u32(node, "max-brightness-level", + &value); + if (ret < 0) + return ret; - num_levels /= sizeof(u32); + data->max_brightness = value; + } else { + num_levels /= sizeof(u32); + } /* read brightness levels from DT property */ if (num_levels > 0) {
@@ -130,14 +137,13 @@ static int pwm_backlight_parse_dt(struct device *dev, return ret; data->max_brightness = num_levels; + } - ret = of_property_read_u32(node, "default-brightness-level", - &value); - if (ret < 0) - return ret; + ret = of_property_read_u32(node, "default-brightness-level", &value); + if (ret < 0) + return ret; - data->dft_brightness = value; - } + data->dft_brightness = value; /* * TODO: Most users of this driver use a number of GPIOs to control
--
1.8.1.1