135 lines
4.8 KiB
Plaintext
135 lines
4.8 KiB
Plaintext
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For pwm-backlight bindings
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1. backlight node
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Required properties:
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- compatible: "pwm-backlight"
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- pwms: OF device-tree PWM specification (see PWM binding[0])
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- lth-brightness: low threshold brightness to retain the linearity of the graph when the intensity
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of backlight goes to zero(OFF) when the value in not zero almost nearing to zero(some x%)
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- pwm-gpio: specifies a GPIO used for pwm pin if there is.
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- bl-measured: Arrays for backlight calibration, which is usually for linear backlight response.
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- brightness-levels: Array of distinct brightness levels. Typically these
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are in the range from 0 to 255, but any range starting at 0 will do.
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The actual brightness level (PWM duty cycle) will be interpolated
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from these values. 0 means a 0% duty cycle (darkest/off), while the
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last value in the array represents a 100% duty cycle (brightest).
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- default-brightness-level: the default brightness level (index into the
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array defined by the "brightness-levels" property)
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- power-supply: regulator for supply voltage
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- label: name of the backlight device. If not specified, node name will be
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be used as device name.
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The following "max-brightness" and "default-brightness" are mutually exclusive
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with "brightness-levels" and "default-brightness-level".
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It is used in case where levels are not available on the backlight device
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and the device can interpolate values.
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In this case the minimum value that is considered is 0.
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- max-brightness: the maximum brighness value that is allowed by the
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backlight device.
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- default-brightness: the default brighness value that is allowed by the
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backlight device.
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Optional properties:
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- pwm-names: a list of names for the PWM devices specified in the
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"pwms" property (see PWM binding[0])
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- enable-gpios: contains a single GPIO specifier for the GPIO which enables
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and disables the backlight (see GPIO binding[1])
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It is possible for backlight node to have child backlight node.
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- Child node represents one of multiple backlight settings nodes, which are pwm-backlight based.
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In this case, "lth-brightness", "pwm-gpio", "bl-measured", "brightness-levels",
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"default-brightness-level", "max-brightness" and "default-brightness" properties
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need to be prepared underneath each child node, instead of backlight parent node.
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1.A) child backlight node
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Child backlight node must be contained in backlight parent node.
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It is possible to have multiple backlight nodes. Additionally, child backlight node
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should have its own compatible property.
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- compatible: Can be arbitrary, but each child backlight node should have unique name.
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- pwms: OF device-tree PWM specification (see PWM binding[0]). If pwms is not searched
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underneath backlight node, then, search pwm device in this node.
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[0]: Documentation/devicetree/bindings/pwm/pwm.txt
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[1]: Documentation/devicetree/bindings/gpio/gpio.txt
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Examples:
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backlight {
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compatible = "pwm-backlight";
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pwms = <&pwm 0 5000000>;
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brightness-levels = <0 4 8 16 32 64 128 255>;
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default-brightness-level = <6>;
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power-supply = <&vdd_bl_reg>;
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enable-gpios = <&gpio 58 0>;
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};
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or
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backlight {
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compatible = "pwm-backlight";
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pwms = <&pwm 1 1000000>;
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max-brightness = <255>;
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default-brightness = <224>;
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};
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or
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backlight {
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compatible = "pwm-backlight";
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pwms = <&pwm 1 5000000>;
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bl-device {
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status = "okay";
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compatible = "a,wuxga-8-0-bl";
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brightness-levels = <0 4 8 16 32 64 128 255>;
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default-brightness-level = <6>;
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};
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};
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or
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backlight {
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compatible = "pwm-backlight";
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pwms = <&pwm 1 40161>;
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bl-device {
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status = "okay";
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compatible = "a,wuxga-8-0-bl";
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max-brightness = <255>;
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default-brightness = <191>;
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bl-measured = < 0 1 2 4 5 6 7 8
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10 11 12 13 14 15 16 18
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19 20 21 22 23 24 25 26
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27 29 30 31 32 33 34 35
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36 38 39 40 41 42 44 45
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46 47 48 49 50 52 53 54
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55 56 57 58 59 61 62 63
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64 65 67 68 69 70 71 72
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73 75 76 77 78 79 80 81
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82 83 84 85 86 87 88 89
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90 91 92 93 94 96 97 98
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99 100 101 102 103 104 105 106
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107 108 109 110 111 112 112 113
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114 115 115 116 117 117 118 119
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120 122 123 124 125 126 128 129
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130 131 132 133 134 135 135 136
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137 138 139 140 141 142 143 145
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146 147 148 149 150 151 152 153
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154 155 156 157 158 159 160 161
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161 162 163 164 164 165 166 166
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167 168 169 170 171 173 174 175
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176 177 178 179 180 181 182 183
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183 184 185 186 187 188 189 189
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190 191 192 193 193 194 195 196
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197 198 199 200 200 201 202 203
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204 205 206 207 208 209 210 211
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212 213 214 216 217 218 219 220
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221 222 223 224 225 226 227 228
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229 230 231 232 233 234 235 235
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236 237 238 239 240 241 242 243
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244 245 247 248 249 250 251 251
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252 252 253 253 254 254 255 255 >;
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};
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};
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