Board: Improve I²C device management to avoid null reference exceptions

src/Iot.Device.Bindings/CompatibilitySuppressions.xml

@@ -14,6 +14,13 @@
     <Right>lib/net6.0/Iot.Device.Bindings.dll</Right>
     <IsBaselineSuppression>true</IsBaselineSuppression>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Iot.Device.Ft232H.Ft232HI2c</Target>
+    <Left>lib/net6.0/Iot.Device.Bindings.dll</Left>
+    <Right>lib/net6.0/Iot.Device.Bindings.dll</Right>
+    <IsBaselineSuppression>true</IsBaselineSuppression>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:IoT.Device.Pn532.ErrorCode</Target>
@@ -147,6 +154,13 @@
     <Right>lib/netstandard2.0/Iot.Device.Bindings.dll</Right>
     <IsBaselineSuppression>true</IsBaselineSuppression>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Iot.Device.Ft232H.Ft232HI2c</Target>
+    <Left>lib/netcoreapp3.1/Iot.Device.Bindings.dll</Left>
+    <Right>lib/netstandard2.0/Iot.Device.Bindings.dll</Right>
+    <IsBaselineSuppression>true</IsBaselineSuppression>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:Iot.Device.Common.ValueArray`1</Target>
@@ -161,6 +175,13 @@
     <Right>lib/netstandard2.0/Iot.Device.Bindings.dll</Right>
     <IsBaselineSuppression>true</IsBaselineSuppression>
   </Suppression>
+  <Suppression>
+    <DiagnosticId>CP0001</DiagnosticId>
+    <Target>T:Iot.Device.Ft232H.Ft232HI2c</Target>
+    <Left>lib/netstandard2.0/Iot.Device.Bindings.dll</Left>
+    <Right>lib/netstandard2.0/Iot.Device.Bindings.dll</Right>
+    <IsBaselineSuppression>true</IsBaselineSuppression>
+  </Suppression>
   <Suppression>
     <DiagnosticId>CP0001</DiagnosticId>
     <Target>T:IoT.Device.Pn532.ErrorCode</Target>

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

@@ -1,13 +1,15 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
-using System.Threading;
+using System.Collections.Generic;
 using System.Device.I2c;
 using System.Device.Pwm;
+using System.Threading;
 using Iot.Device.Adc;
 using Iot.Device.Bmxx80;
-using Xunit;
+using Iot.Device.Board;
 using UnitsNet;
+using Xunit;
 using static System.Device.Gpio.Tests.SetupHelpers;
 
 namespace System.Device.Gpio.Tests;
@@ -100,6 +102,67 @@ public void I2C_I2cBus_MultipleDispose()
         bme280.Dispose();
     }
 
+    [Fact]
+    [Trait("feature", "i2c")]
+    public void I2C_I2cBus_MultipleCreate()
+    {
+        I2cBus i2cBus = CreateI2cBusForBme280();
+
+        I2cDevice device1 = i2cBus.CreateDevice(Bmp280.DefaultI2cAddress);
+        device1.ReadByte();
+        i2cBus.RemoveDevice(Bmp280.DefaultI2cAddress);
+
+        I2cDevice device2 = i2cBus.CreateDevice(Bmp280.DefaultI2cAddress);
+        device2.ReadByte();
+    }
+
+    [Fact]
+    [Trait("feature", "i2c")]
+    public void I2C_I2cBus_MultipleCreateAndDispose()
+    {
+        I2cBus i2cBus = CreateI2cBusForBme280();
+
+        I2cDevice device1 = i2cBus.CreateDevice(Bmp280.DefaultI2cAddress);
+        device1.ReadByte();
+        device1.Dispose();
+
+        I2cDevice device2 = i2cBus.CreateDevice(Bmp280.DefaultI2cAddress);
+        device2.ReadByte();
+        device2.Dispose();
+    }
+
+    [Fact]
+    [Trait("feature", "i2c")]
+    public void I2C_I2cBus_Scan()
+    {
+        I2cBus i2cBus = CreateI2cBusForBme280();
+        List<int> addresses = i2cBus.PerformBusScan();
+        Assert.NotNull(addresses);
+    }
+
+    [Fact]
+    [Trait("feature", "i2c")]
+    public void I2C_I2cBus_ScanMultipleTimes()
+    {
+        I2cBus i2cBus = CreateI2cBusForBme280();
+
+        List<int> addresses1 = i2cBus.PerformBusScan();
+        Assert.NotNull(addresses1);
+
+        List<int> addresses2 = i2cBus.PerformBusScan();
+        Assert.NotNull(addresses2);
+    }
+
+    [Fact]
+    [Trait("feature", "i2c")]
+    public void I2C_I2cBus_HasBmp280Present()
+    {
+        I2cBus i2cBus = CreateI2cBusForBme280();
+        List<int> addresses = i2cBus.PerformBusScan();
+        Assert.NotEmpty(addresses);
+        Assert.Contains(Bmp280.DefaultI2cAddress, addresses);
+    }
+
     [Fact]
     [Trait("feature", "pwm")]
     [Trait("feature", "spi")]

src/devices/Board/I2cBusManager.cs

@@ -68,13 +68,8 @@ public I2cBusManager(Board board, int bus, int[]? pins, I2cBus busInstance)
         /// <remarks>No test is performed whether the given device exists and is usable</remarks>
         public override I2cDevice CreateDevice(int deviceAddress)
         {
-            if (_devices.TryGetValue(deviceAddress, out I2cDevice? device))
-            {
-                return device;
-            }
-
             I2cDevice newDevice = _busInstance.CreateDevice(deviceAddress);
-            _devices.Add(deviceAddress, newDevice);
+            _devices[deviceAddress] = newDevice;
             return newDevice;
         }
 

src/devices/Board/tests/BoardTests.cs

@@ -185,6 +185,34 @@ public void TwoI2cDevicesCanSharePins()
             ctrl.OpenPin(0);
         }
 
+        [Fact]
+        public void CreateAndRemoveI2cDevice()
+        {
+            using Board board = CreateBoard();
+            I2cBus bus = board.CreateOrGetI2cBus(0);
+
+            I2cDevice device1 = bus.CreateDevice(0x55);
+            device1.ReadByte();
+            bus.RemoveDevice(0x55);
+
+            I2cDevice device2 = bus.CreateDevice(0x55);
+            device2.ReadByte();
+        }
+
+        [Fact]
+        public void CreateAndDisposeI2cDevice()
+        {
+            using Board board = CreateBoard();
+            I2cBus bus = board.CreateOrGetI2cBus(0);
+
+            I2cDevice device1 = bus.CreateDevice(0x55);
+            device1.ReadByte();
+            device1.Dispose();
+
+            I2cDevice device2 = bus.CreateDevice(0x55);
+            device2.ReadByte();
+        }
+
         [Fact]
         public void CreateSpiDeviceDefault()
         {

src/devices/Ft232H/Ft232H.csproj

@@ -9,8 +9,8 @@
     <Compile Include="Ft2232HDevice.cs" />
     <Compile Include="Ft232HDevice.cs" />
     <Compile Include="Ft232HGpio.cs" />
-    <Compile Include="Ft232HI2c.cs" />
     <Compile Include="Ft232HI2cBus.cs" />
+    <Compile Include="Ft232HI2cDevice.cs" />
     <Compile Include="Ft232HSpi.cs" />
     <Compile Include="Ft4232HDevice.cs" />
     <Compile Include="Ftx232HDevice.cs" />

src/devices/Ft232H/Ft232HI2cBus.cs

@@ -15,7 +15,7 @@ namespace Iot.Device.Ft232H
     /// </summary>
     internal class Ft232HI2cBus : I2cBus
     {
-        private HashSet<int> _usedAddresses = new HashSet<int>();
+        private HashSet<int>? _usedAddresses = null;
 
         /// <summary>
         /// Store the FTDI Device Information
@@ -35,23 +35,34 @@ public Ft232HI2cBus(Ftx232HDevice deviceInformation)
         /// <inheritdoc/>
         public override I2cDevice CreateDevice(int deviceAddress)
         {
+            _usedAddresses ??= new HashSet<int>();
             if (!_usedAddresses.Add(deviceAddress))
             {
                 throw new ArgumentException($"Device with address 0x{deviceAddress,0X2} is already open.", nameof(deviceAddress));
             }
 
-            return new Ft232HI2c(this, deviceAddress);
+            return CreateDeviceNoCheck(deviceAddress);
+        }
+
+        internal I2cDevice CreateDeviceNoCheck(int deviceAddress)
+        {
+            return new Ft232HI2cDevice(this, deviceAddress);
         }
 
         /// <inheritdoc/>
         public override void RemoveDevice(int deviceAddress)
         {
-            if (!_usedAddresses.Remove(deviceAddress))
+            if (!RemoveDeviceNoCheck(deviceAddress))
             {
                 throw new ArgumentException($"Device with address 0x{deviceAddress,0X2} was not open.", nameof(deviceAddress));
             }
         }
 
+        internal bool RemoveDeviceNoCheck(int deviceAddress)
+        {
+            return _usedAddresses?.Remove(deviceAddress) ?? false;
+        }
+
         internal void Read(int deviceAddress, Span<byte> buffer)
         {
             DeviceInformation.I2cStart();

src/devices/Ft232H/Ft232HI2c.cs → src/devices/Ft232H/Ft232HI2cDevice.cs

@@ -9,17 +9,19 @@ namespace Iot.Device.Ft232H
     /// <summary>
     /// I2C Device for FT232H
     /// </summary>
-    public class Ft232HI2c : I2cDevice
+    public class Ft232HI2cDevice : I2cDevice
     {
         private Ft232HI2cBus _i2cBus;
         private int _deviceAddress;
         private I2cConnectionSettings _settings;
+        private bool _shouldDisposeBus;
 
-        internal Ft232HI2c(Ft232HI2cBus i2cBus, int deviceAddress)
+        internal Ft232HI2cDevice(Ft232HI2cBus i2cBus, int deviceAddress, bool shouldDisposeBus = false)
         {
             _i2cBus = i2cBus;
             _deviceAddress = deviceAddress;
             _settings = new I2cConnectionSettings((int)i2cBus.DeviceInformation.LocId, deviceAddress);
+            _shouldDisposeBus = shouldDisposeBus;
         }
 
         /// <inheritdoc/>
@@ -47,9 +49,22 @@ public override void WriteRead(ReadOnlySpan<byte> writeBuffer, Span<byte> readBu
         /// <inheritdoc/>
         protected override void Dispose(bool disposing)
         {
-            _i2cBus?.RemoveDevice(_deviceAddress);
-            _i2cBus = null!;
+            if (_i2cBus != null)
+            {
+                if (_shouldDisposeBus)
+                {
+                    _i2cBus.Dispose();
+                }
+                else
+                {
+                    _i2cBus.RemoveDeviceNoCheck(_deviceAddress);
+                }
+
+                _i2cBus = null!;
+            }
+
             _settings = null!;
+
             base.Dispose(disposing);
         }