arch/arm/boot/dts/overlays/hdmi-backlight-hwhack-gpio-overlay.dts

   1 /*
   2  * Devicetree overlay for GPIO based backlight on/off capability.
   3  *
   4  * Use this if you have one of those HDMI displays whose backlight cannot be
   5  * controlled via DPMS over HDMI and plan to do a little soldering to use an
   6  * RPi gpio pin for on/off switching.
   7  *
   8  * See: https://www.waveshare.com/wiki/7inch_HDMI_LCD_(C)#Backlight_Control
   9  *
  10  */
  11 /dts-v1/;
  12 /plugin/;
  13
  14 / {
  15         compatible = "brcm,bcm2835";
  16
  17         fragment@1 {
  18                 target = <&gpio>;
  19                 __overlay__ {
  20                         hdmi_backlight_hwhack_gpio_pins: hdmi_backlight_hwhack_gpio_pins {
  21                                 brcm,pins = <17>;
  22                                 brcm,function = <1>; /* out */
  23                         };
  24                 };
  25         };
  26
  27         fragment@2 {
  28                 target-path = "/";
  29                 __overlay__ {
  30                         hdmi_backlight_hwhack_gpio: hdmi_backlight_hwhack_gpio {
  31                                 compatible = "gpio-backlight";
  32
  33                                 pinctrl-names = "default";
  34                                 pinctrl-0 = <&hdmi_backlight_hwhack_gpio_pins>;
  35
  36                                 gpios = <&gpio 17 0>;
  37                                 default-on;
  38                         };
  39                 };
  40         };
  41
  42         __overrides__ {
  43                 gpio_pin   = <&hdmi_backlight_hwhack_gpio>,"gpios:4",
  44                              <&hdmi_backlight_hwhack_gpio_pins>,"brcm,pins:0";
  45                 active_low = <&hdmi_backlight_hwhack_gpio>,"gpios:8";
  46         };
  47 };