raspberry-pi/4: add led disable overlay

raspberry-pi/4/default.nix

@@ -8,6 +8,7 @@
     ./digi-amp-plus.nix
     ./dwc2.nix
     ./i2c.nix
+    ./leds.nix
     ./modesetting.nix
     ./pkgs-overlays.nix
     ./poe-hat.nix

raspberry-pi/4/leds.nix

@@ -0,0 +1,116 @@
+{ config, lib, ... }:
+
+let
+  cfg = config.hardware.raspberry-pi."4".leds;
+in
+{
+  options.hardware = {
+    raspberry-pi."4".leds = {
+      disable-eth = lib.mkEnableOption ''
+        disable ethernet LEDs.
+      '';
+      disable-act = lib.mkEnableOption ''
+        disable activity LED.
+      '';
+      disable-pwr = lib.mkEnableOption ''
+        disable power LED.
+      '';
+    };
+  };
+
+  # Adapted from: https://gist.github.com/SFrijters/206d2c09656affb04284f076c75a1969
+  config = lib.mkMerge [
+    (lib.mkIf cfg.disable-eth {
+      hardware.deviceTree = {
+        overlays = [
+          # https://github.com/raspberrypi/firmware/blob/master/boot/overlays/README
+          # eth_led0                Set mode of LED0 - amber on Pi3B+ (default "1"),
+          #                         green on Pi4 (default "0").
+          #                         The legal values are:
+          #
+          #                         Pi4
+          #
+          #                         0=Speed/Activity         1=Speed
+          #                         2=Flash activity         3=FDX
+          #                         4=Off                    5=On
+          #                         6=Alt                    7=Speed/Flash
+          #                         8=Link                   9=Activity
+          #
+          # Debugging:
+          # $ hexdump /proc/device-tree/scb/ethernet@7d580000/mdio@e14/ethernet-phy@1/led-modes
+          {
+            name = "disable-eth-leds";
+            filter = "*rpi-4-b*";
+            dtsText = ''
+              /dts-v1/;
+              /plugin/;
+              /{
+                  compatible = "raspberrypi,4-model-b";
+                  fragment@0 {
+                      target = <&phy1>;
+                      __overlay__ {
+                          led-modes = <0x04 0x04>;
+                      };
+                  };
+              };
+            '';
+          }
+        ];
+      };
+    })
+    (lib.mkIf cfg.disable-act {
+      hardware.deviceTree = {
+        overlays = [
+          # Debugging:
+          # $ hexdump /proc/device-tree/leds/led-act/gpios
+          # $ cat /proc/device-tree/leds/led-act/linux,default-trigger
+          {
+            name = "disable-act-led";
+            filter = "*rpi-4-b*";
+            dtsText = ''
+              /dts-v1/;
+              /plugin/;
+              /{
+                  compatible = "raspberrypi,4-model-b";
+                  fragment@0 {
+                      target = <&act_led>;
+                      __overlay__ {
+                          gpios = <&gpio 42 0>; /* first two values copied from bcm2711-rpi-4-b.dts */
+                          linux,default-trigger = "none";
+                      };
+                  };
+              };
+            '';
+          }
+        ];
+      };
+    })
+    (lib.mkIf cfg.disable-pwr {
+      hardware.deviceTree = {
+        overlays = [
+          # Debugging:
+          # $ hexdump /proc/device-tree/leds/led-pwr/gpios
+          # $ cat /proc/device-tree/leds/led-pwr/linux,default-trigger
+          {
+            name = "disable-pwr-led";
+            filter = "*rpi-4-b*";
+            dtsText = ''
+              /dts-v1/;
+              /plugin/;
+              /{
+                  compatible = "raspberrypi,4-model-b";
+                  fragment@0 {
+                      target = <&pwr_led>;
+                      __overlay__ {
+                          gpios = <&expgpio 2 0>; /* first two values copied from bcm2711-rpi-4-b.dts */
+                          linux,default-trigger = "default-on";
+                      };
+                  };
+              };
+            '';
+          }
+        ];
+      };
+    })
+  ];
+}