Configure ADS7846 touchscreen with matrix

Signed-off-by: Mel <mel@rnrd.eu>

1 files changed, 121 insertions, 90 deletions

diff --git a/modules/hardware/ads7846.nix b/modules/hardware/ads7846.nix
index cf1131e..bb1fe61 100644
--- a/modules/hardware/ads7846.nix
+++ b/modules/hardware/ads7846.nix
@@ -1,104 +1,135 @@
 { ... }:
 
 {
-  hardware.deviceTree = {
-    overlays = [
-      {
-        name = "ads7846-overlay";
-        # taken from raspberry-pi kernel tree:
-        # https://github.com/raspberrypi/linux/blob/rpi-6.6.y/arch/arm/boot/dts/overlays/ads7846-overlay.dts
-        dtsText = ''
-          		  /*
-          		  * Generic Device Tree overlay for the ADS7846 touch controller
-          		  *
-          		  */
+  # calibration for touchscreen
+  services =
+    let
+      calibrationPoints = "3900 200 200 3900";
+      calibrationMatrix = "-1 0 1 0 1 0 0 0 1";
+    in
+    {
+      libinput.enable = true;
 
-          		  /dts-v1/;
-          		  /plugin/;
+      # xorg configuration
+      xserver.inputClassSections = [
+        ''
+          Identifier	"ads7846 calibration"
+          MatchProduct	"ADS7846 Touchscreen"
+          Option	"Calibration"	"${calibrationPoints}"
+          Option	"SwapAxes"	"0"
+          Driver  "libinput"
+        ''
+      ];
 
-          		  / {
-          			  compatible = "brcm,bcm2835";
+      # wayland configuration
+      udev.extraRules = ''
+        ATTRS{name}=="ADS7846 Touchscreen", ENV{LIBINPUT_CALIBRATION_MATRIX}="${calibrationMatrix}"
+      '';
+    };
 
-          			  fragment@0 {
-          				  target = <&spi0>;
-          				  __overlay__ {
-          					  status = "okay";
-          				  };
-          			  };
+  hardware.deviceTree =
+    let
+      # todo: parameter-ize this more.
+      penirq = 25;
+    in
+    {
+      overlays = [
+        {
+          name = "ads7846-overlay";
+          # taken from raspberry-pi kernel tree:
+          # https://github.com/raspberrypi/linux/blob/rpi-6.6.y/arch/arm/boot/dts/overlays/ads7846-overlay.dts
+          dtsText = ''
+            /*
+            * Generic Device Tree overlay for the ADS7846 touch controller
+            *
+            */
 
-          			  fragment@1 {
-          				  target = <&spidev0>;
-          				  __overlay__ {
-          					  status = "disabled";
-          				  };
-          			  };
+            /dts-v1/;
+            /plugin/;
 
-          			  fragment@2 {
-          				  target = <&spidev1>;
-          				  __overlay__ {
-          					  status = "disabled";
-          				  };
-          			  };
+            / {
+                    compatible = "brcm,bcm2711";
 
-          			  fragment@3 {
-          				  target = <&gpio>;
-          				  __overlay__ {
-          					  ads7846_pins: ads7846_pins {
-          						  brcm,pins = <255>; /* illegal default value */
-          						  brcm,function = <0>; /* in */
-          						  brcm,pull = <0>; /* none */
-          					  };
-          				  };
-          			  };
+                    fragment@0 {
+                            target = <&spi0>;
+                            __overlay__ {
+                                    status = "okay";
+                            };
+                    };
 
-          			  fragment@4 {
-          				  target = <&spi0>;
-          				  __overlay__ {
-          					  /* needed to avoid dtc warning */
-          					  #address-cells = <1>;
-          					  #size-cells = <0>;
+                    fragment@1 {
+                            target = <&spidev0>;
+                            __overlay__ {
+                                    status = "disabled";
+                            };
+                    };
 
-          					  ads7846: ads7846@1 {
-          						  compatible = "ti,ads7846";
-          						  reg = <1>;
-          						  pinctrl-names = "default";
-          						  pinctrl-0 = <&ads7846_pins>;
+                    fragment@2 {
+                            target = <&spidev1>;
+                            __overlay__ {
+                                    status = "disabled";
+                            };
+                    };
 
-          						  spi-max-frequency = <2000000>;
-          						  interrupts = <255 2>; /* high-to-low edge triggered */
-          						  interrupt-parent = <&gpio>;
-          						  pendown-gpio = <&gpio 255 1>;
+                    fragment@3 {
+                            target = <&gpio>;
+                            __overlay__ {
+                                    ads7846_pins: ads7846_pins {
+                                            brcm,pins = <${toString penirq}>; /* mel: previously illegal value of 255 */
+                                            brcm,function = <0>; /* in */
+                                            brcm,pull = <0>; /* none */
+                                    };
+                            };
+                    };
 
-          						  /* driver defaults */
-          						  ti,x-min = /bits/ 16 <0>;
-          						  ti,y-min = /bits/ 16 <0>;
-          						  ti,x-max = /bits/ 16 <0x0FFF>;
-          						  ti,y-max = /bits/ 16 <0x0FFF>;
-          						  ti,pressure-min = /bits/ 16 <0>;
-          						  ti,pressure-max = /bits/ 16 <0xFFFF>;
-          						  ti,x-plate-ohms = /bits/ 16 <400>;
-          					  };
-          				  };
-          			  };
-          			  __overrides__ {
-          				  cs =     <&ads7846>,"reg:0";
-          				  speed =  <&ads7846>,"spi-max-frequency:0";
-          				  penirq = <&ads7846_pins>,"brcm,pins:0", /* REQUIRED */
-          					  <&ads7846>,"interrupts:0",
-          					  <&ads7846>,"pendown-gpio:4";
-          				  penirq_pull = <&ads7846_pins>,"brcm,pull:0";
-          				  swapxy = <&ads7846>,"ti,swap-xy?";
-          				  xmin =   <&ads7846>,"ti,x-min;0";
-          				  ymin =   <&ads7846>,"ti,y-min;0";
-          				  xmax =   <&ads7846>,"ti,x-max;0";
-          				  ymax =   <&ads7846>,"ti,y-max;0";
-          				  pmin =   <&ads7846>,"ti,pressure-min;0";
-          				  pmax =   <&ads7846>,"ti,pressure-max;0";
-          				  xohms =  <&ads7846>,"ti,x-plate-ohms;0";
-          			  };
-          		  };
-        '';
-      }
-    ];
-  };
+                    fragment@4 {
+                            target = <&spi0>;
+                            __overlay__ {
+                                    /* needed to avoid dtc warning */
+                                    #address-cells = <1>;
+                                    #size-cells = <0>;
+
+                                    ads7846: ads7846@1 {
+                                            compatible = "ti,ads7846";
+                                            reg = <1>;
+                                            pinctrl-names = "default";
+                                            pinctrl-0 = <&ads7846_pins>;
+
+                                            spi-max-frequency = <2000000>;
+                                            interrupts = <${toString penirq} 2>; /* high-to-low edge triggered */
+                                            interrupt-parent = <&gpio>;
+                                            pendown-gpio = <&gpio ${toString penirq} 1>;
+
+                                            /* driver defaults */
+                                            ti,x-min = /bits/ 16 <0>;
+                                            ti,y-min = /bits/ 16 <0>;
+                                            ti,x-max = /bits/ 16 <0x0FFF>;
+                                            ti,y-max = /bits/ 16 <0x0FFF>;
+                                            ti,pressure-min = /bits/ 16 <0>;
+                                            ti,pressure-max = /bits/ 16 <0xFFFF>;
+                                            ti,x-plate-ohms = /bits/ 16 <400>;
+                                    };
+                            };
+                    };
+                    __overrides__ {
+                            cs =     <&ads7846>,"reg:0";
+                            speed =  <&ads7846>,"spi-max-frequency:0";
+                            penirq = <&ads7846_pins>,"brcm,pins:0", /* REQUIRED */
+                                    <&ads7846>,"interrupts:0",
+                                    <&ads7846>,"pendown-gpio:4";
+                            penirq_pull = <&ads7846_pins>,"brcm,pull:0";
+                            swapxy = <&ads7846>,"ti,swap-xy?";
+                            xmin =   <&ads7846>,"ti,x-min;0";
+                            ymin =   <&ads7846>,"ti,y-min;0";
+                            xmax =   <&ads7846>,"ti,x-max;0";
+                            ymax =   <&ads7846>,"ti,y-max;0";
+                            pmin =   <&ads7846>,"ti,pressure-min;0";
+                            pmax =   <&ads7846>,"ti,pressure-max;0";
+                            xohms =  <&ads7846>,"ti,x-plate-ohms;0";
+                    };
+            };
+          '';
+        }
+      ];
+    };
 }