Add support for RPi CM4 GPIO (#1714)

src/System.Device.Gpio.Tests/RaspberryPiDriverTests.cs

@@ -33,7 +33,7 @@ namespace System.Device.Gpio.Tests
             if (File.Exists("/proc/device-tree/model"))
             {
                 string model = File.ReadAllText("/proc/device-tree/model", Text.Encoding.ASCII);
-                if (model.Contains("Raspberry Pi 4"))
+                if (model.Contains("Raspberry Pi 4") || model.Contains("Raspberry Pi Compute Module 4"))
                 {
                     return true;
                 }

src/System.Device.Gpio/System/Device/Gpio/Drivers/RaspberryPi3Driver.cs

@@ -138,7 +138,8 @@ namespace System.Device.Gpio.Drivers
                 RaspberryBoardInfo.Model.RaspberryPi3B or
                 RaspberryBoardInfo.Model.RaspberryPi3APlus or
                 RaspberryBoardInfo.Model.RaspberryPi3BPlus or
-                RaspberryBoardInfo.Model.RaspberryPi4 => new RaspberryPi3LinuxDriver(),
+                RaspberryBoardInfo.Model.RaspberryPi4 or
+                RaspberryBoardInfo.Model.RaspberryPiComputeModule4 => new RaspberryPi3LinuxDriver(),
                 RaspberryBoardInfo.Model.RaspberryPiComputeModule3 => new RaspberryPiCm3Driver(),
                 _ => null,
             };

src/System.Device.Gpio/System/Device/Gpio/RaspberryBoardInfo.cs

@@ -96,6 +96,11 @@ namespace System.Device.Gpio
             /// Pi 400
             /// </summary>
             RaspberryPi400,
+
+            /// <summary>
+            /// Compute module 4.
+            /// </summary>
+            RaspberryPiComputeModule4,
         }
 
         #region Fields
@@ -153,6 +158,7 @@ namespace System.Device.Gpio
             0x20E0 => Model.RaspberryPi3APlus,
             0x20A0 or 0x2100 => Model.RaspberryPiComputeModule3,
             0x3111 or 0x3112 or 0x3114 => Model.RaspberryPi4,
+            0x3140 => Model.RaspberryPiComputeModule4,
             0x3130 => Model.RaspberryPi400,
             _ => Model.Unknown,
         };