Add libgpiodv2 support

Documentation/README.md

@@ -118,6 +118,14 @@ While contributing, you should read the [coding guidelines section](https://gith
 
 * [PINE A64-LTS](https://www.pine64.org/?page_id=46823)
 
+## Platforms
+
+### Linux
+
+#### GPIO
+
+* [Use libgpiod to control GPIOs on Linux](./gpio-linux-libgpiod.md)
+
 ## Maker Resources
 
 ### Prototyping

Documentation/gpio-linux-libgpiod.md

@@ -0,0 +1,109 @@
+# Using libgpiod to control GPIOs
+
+## Quick usage: blink LED example
+
+This example targets a RaspberryPi 3/4, see comments for more information:
+
+```c#
+// side note: on the Raspberry Pi the GPIO chip line offsets are the same numbers as the usual BCM GPIO numbering, which is convenient
+const int ledGpio = 15;
+
+// on the Pi3,4 you most likely want 0, on the Pi5 number 4, see 'gpioinfo' tool
+const int chipNumber = 0;
+// 'using' will dispose the controller when it falls out of scope, which will un-claim lines
+
+// alternatively be more explicit: 'new GpioController(chipNumber, new LibGpiodDriver())'
+using var gpioController = new GpioController(chipNumber);
+
+gpioController.OpenPin(ledGpio);
+
+for (int i = 0; i < 5; i++)
+{
+    controller.Write(ledGpio, PinValue.High);
+    await Task.Delay(1000);
+    controller.Write(ledGpio, PinValue.Low);
+    await Task.Delay(1000);
+}
+```
+
+## libgpiod versions
+
+**Note**: The documented version of libgpiod is not the same as the library so name, see the following table:
+
+| Documented version | Library so name   | Comment                                                  |
+| ------------------ | ----------------- | -------------------------------------------------------- |
+| 1.0.2              | libgpiod.so.1.0.2 | last .so.1.x library                                     |
+| 1.1                | libgpiod.so.2.0.0 | first occurrence of inconsistency, first .so.2.x library |
+| 1.6.4              | libgpiod.so.2.2.2 | last .so.2.x library                                     |
+| 2.0                | libgpiod.so.3.0.0 | first .so.3.x library                                    |
+| 2.1                | libgpiod.so.3.1.0 | latest .so.3.x library (currently)                       |
+
+## libgpiod version support
+
+Currently (12/23) dotnet-iot supports v0, v1 and v2 of libgpiod.
+
+The following table shows which driver supports which library version
+
+| LibGpiodDriverVersion | Libgpiod version (documented) |
+| --------------------- | ----------------------------- |
+| V1                    | 0.x to 1.x                    |
+| V2                    | 2.x                           |
+
+## Choose LibGpiodDriver Version
+
+If you want to explicitly select the version of the libgpiod driver, to target a specific library version, there are following options:
+
+1. constructor of LibGpiodDriver:
+
+   ```c#
+   new LibGpiodDriver(chipNumber, LibGpiodDriverVersion.V1)
+   ```
+
+2. Environment variable:
+
+   ```shell
+   export DOTNET_IOT_LIBGPIOD_DRIVER_VERSION=V1 // or V2...
+   ```
+
+When not explicitly specified, dotnet iot automatically tries to find a driver compatible to what library version is installed.
+
+## Install libgpiod
+
+If you want to control GPIOs using libgpiod, the library must be installed.
+
+Many package managers provide a libgpiod package, for example:
+
+   ```shell
+   apt install libgpiod2
+   ```
+
+## Install libgpiod manually
+
+The installation should be the same on all Pi's, or boards whose distro uses the APT package manager.
+
+1. Install build dependencies
+
+   ```shell
+   sudo apt update && sudo apt install -y autogen autoconf autoconf-archive libtool libtool-bin pkg-config build-essential
+   ```
+
+2. Download the tarball and unpack it, see [releases](https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/refs/), e.g.
+
+   ```shell
+   wget https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/snapshot/libgpiod-2.1.tar.gz
+   tar -xzf libgpiod-2.1.tar.gz
+   ```
+
+3. Compile and install (see [docs](https://git.kernel.org/pub/scm/libs/libgpiod/libgpiod.git/about/))
+
+   ```shell
+   cd libgpiod-2.1/
+   ./autogen.sh
+   make
+   sudo make install
+   sudo ldconfig
+   ```
+
+This will install the library .so files to `/usr/lib/local`
+
+If you want to also build command line utilities `gpioinfo, gpiodetect` etc., specify `./autogen.sh --enable-tools=yes`

src/System.Device.Gpio.Tests/LibGpiodDriverTests.cs → src/System.Device.Gpio.Tests/LibGpiodV1DriverTests.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Device.Gpio.Drivers;
+using System.Device.Gpio.Drivers.Libgpiod.V1;
 using System.Threading;
 using Xunit;
 using Xunit.Abstractions;
@@ -11,14 +12,14 @@ namespace System.Device.Gpio.Tests;
 [Trait("feature", "gpio")]
 [Trait("feature", "gpio-libgpiod")]
 [Trait("SkipOnTestRun", "Windows_NT")]
-public class LibGpiodDriverTests : GpioControllerTestBase
+public class LibGpiodV1DriverTests : GpioControllerTestBase
 {
-    public LibGpiodDriverTests(ITestOutputHelper testOutputHelper)
+    public LibGpiodV1DriverTests(ITestOutputHelper testOutputHelper)
         : base(testOutputHelper)
     {
     }
 
-    protected override GpioDriver GetTestDriver() => new LibGpiodDriver();
+    protected override GpioDriver GetTestDriver() => new LibGpiodDriver(0, LibGpiodDriverVersion.V1);
 
     protected override PinNumberingScheme GetTestNumberingScheme() => PinNumberingScheme.Logical;
 

src/System.Device.Gpio.Tests/LibGpiodV2DriverTests.cs

@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Device.Gpio.Drivers;
+using System.Diagnostics;
+using System.Threading.Tasks;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace System.Device.Gpio.Tests;
+
+[Trait("feature", "gpio")]
+[Trait("feature", "gpio-libgpiod")]
+[Trait("SkipOnTestRun", "Windows_NT")]
+public class LibGpiodV2DriverTests : GpioControllerTestBase
+{
+    private const int ChipNumber = 0;
+
+    public LibGpiodV2DriverTests(ITestOutputHelper testOutputHelper)
+        : base(testOutputHelper)
+    {
+    }
+
+    protected override GpioDriver GetTestDriver() => new LibGpiodDriver(ChipNumber, LibGpiodDriverVersion.V2);
+
+    protected override PinNumberingScheme GetTestNumberingScheme() => PinNumberingScheme.Logical;
+}

src/System.Device.Gpio/Interop/Unix/Libc/Interop.epoll_ctl.cs

@@ -11,7 +11,7 @@
 internal partial class Interop
 {
     [DllImport(LibcLibrary)]
-    internal static extern int epoll_ctl(int epfd, PollOperations op, int fd, ref epoll_event events);
+    internal static extern int epoll_ctl(int epfd, PollOperations op, int fd, ref epoll_event @event);
 }
 
 internal enum PollOperations
@@ -26,10 +26,12 @@ internal struct epoll_event
     public epoll_data data;
 }
 
+[Flags]
 internal enum PollEvents : uint
 {
     EPOLLIN = 0x01,
     EPOLLPRI = 0x02,
+    EPOLLERR = 0x08,
     EPOLLET = 0x80000000
 }
 

src/System.Device.Gpio/Interop/Unix/Libc/Interop.epoll_wait.cs

@@ -4,10 +4,11 @@
 // Disable these StyleCop rules for this file, as we are using native names here.
 #pragma warning disable SA1300 // Element should begin with upper-case letter
 
+using System;
 using System.Runtime.InteropServices;
 
 internal partial class Interop
 {
     [DllImport(LibcLibrary, SetLastError = true)]
-    internal static extern int epoll_wait(int epfd, out epoll_event events, int maxevents, int timeout);
+    internal static extern int epoll_wait(int epfd, IntPtr events, int maxevents, int timeout);
 }

src/System.Device.Gpio/Interop/Unix/Libc/Interop.pipe.cs

@@ -0,0 +1,13 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+// Disable these StyleCop rules for this file, as we are using native names here.
+#pragma warning disable SA1300 // Element should begin with upper-case letter
+
+using System.Runtime.InteropServices;
+
+internal partial class Interop
+{
+    [DllImport(LibcLibrary, SetLastError = true)]
+    internal static extern int pipe(int[] pipefd);
+}

src/System.Device.Gpio/Interop/Unix/libgpiod/Interop.libgpiod.cs → src/System.Device.Gpio/Interop/Unix/libgpiod/V1/Interop.libgpiod.cs

@@ -7,6 +7,7 @@
 
 using System;
 using System.Device.Gpio;
+using System.Device.Gpio.Libgpiod.V1;
 using System.Runtime.InteropServices;
 #if NET6_0_OR_GREATER
 using System.Runtime.Loader;
@@ -17,7 +18,7 @@
 
 internal partial class Interop
 {
-    internal static partial class Libgpiod
+    internal static partial class LibgpiodV1
     {
 #if NET6_0_OR_GREATER
         private const string LibgpiodLibrary = "libgpiod.so.2";
@@ -26,11 +27,11 @@ internal static partial class Libgpiod
 #endif
         internal static IntPtr InvalidHandleValue;
 
-        static Libgpiod()
+        static LibgpiodV1()
         {
             InvalidHandleValue = new IntPtr(-1);
 #if NET6_0_OR_GREATER
-            Assembly currentAssembly = typeof(Libgpiod).Assembly;
+            Assembly currentAssembly = typeof(LibgpiodV1).Assembly;
 
             AssemblyLoadContext.GetLoadContext(currentAssembly)!.ResolvingUnmanagedDll += (assembly, libgpiodName) =>
             {

src/System.Device.Gpio/Interop/Unix/SafeChipHandle.cs → src/System.Device.Gpio/Interop/Unix/libgpiod/V1/SafeChipHandle.cs

@@ -2,8 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Runtime.InteropServices;
+using LibgpiodV1 = Interop.LibgpiodV1;
 
-namespace System.Device.Gpio;
+namespace System.Device.Gpio.Libgpiod.V1;
 
 /// <summary>
 /// Pointer to a general-purpose I/O (GPIO) chip.
@@ -17,9 +18,9 @@ public SafeChipHandle()
 
     protected override bool ReleaseHandle()
     {
-        Interop.Libgpiod.gpiod_chip_close(handle);
+        LibgpiodV1.gpiod_chip_close(handle);
         return true;
     }
 
-    public override bool IsInvalid => handle == IntPtr.Zero || handle == Interop.Libgpiod.InvalidHandleValue;
+    public override bool IsInvalid => handle == IntPtr.Zero || handle == LibgpiodV1.InvalidHandleValue;
 }

src/System.Device.Gpio/Interop/Unix/SafeChipIteratorHandle.cs → src/System.Device.Gpio/Interop/Unix/libgpiod/V1/SafeChipIteratorHandle.cs

@@ -2,8 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Runtime.InteropServices;
+using LibgpiodV1 = Interop.LibgpiodV1;
 
-namespace System.Device.Gpio;
+namespace System.Device.Gpio.Libgpiod.V1;
 
 /// <summary>
 /// Pointer to an iterator of all GPIO chips available on the device.
@@ -17,9 +18,9 @@ public SafeChipIteratorHandle()
 
     protected override bool ReleaseHandle()
     {
-        Interop.Libgpiod.gpiod_chip_iter_free(handle);
+        LibgpiodV1.gpiod_chip_iter_free(handle);
         return true;
     }
 
-    public override bool IsInvalid => handle == IntPtr.Zero || handle == Interop.Libgpiod.InvalidHandleValue;
+    public override bool IsInvalid => handle == IntPtr.Zero || handle == LibgpiodV1.InvalidHandleValue;
 }

src/System.Device.Gpio/Interop/Unix/SafeLineHandle.cs → src/System.Device.Gpio/Interop/Unix/libgpiod/V1/SafeLineHandle.cs

@@ -2,8 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Runtime.InteropServices;
+using LibgpiodV1 = Interop.LibgpiodV1;
 
-namespace System.Device.Gpio;
+namespace System.Device.Gpio.Libgpiod.V1;
 
 /// <summary>
 /// Pointer to a pin.
@@ -20,17 +21,17 @@ public SafeLineHandle()
     protected override bool ReleaseHandle()
     {
         // Contrary to intuition, this does not invalidate the handle (see comment on declaration)
-        Interop.Libgpiod.gpiod_line_release(handle);
+        LibgpiodV1.gpiod_line_release(handle);
         return true;
     }
 
     /// <summary>
-    /// Release the lock on the line handle. <see cref="Interop.Libgpiod.gpiod_line_release"/>
+    /// Release the lock on the line handle. <see cref="LibgpiodV1.gpiod_line_release"/>
     /// </summary>
     public void ReleaseLock()
     {
         ReleaseHandle();
     }
 
-    public override bool IsInvalid => handle == IntPtr.Zero || handle == Interop.Libgpiod.InvalidHandleValue;
+    public override bool IsInvalid => handle == IntPtr.Zero || handle == LibgpiodV1.InvalidHandleValue;
 }

src/System.Device.Gpio/Interop/Unix/libgpiod/V2/Binding/Enums/GpiodEdgeEventType.cs

@@ -0,0 +1,11 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Device.Gpio.Libgpiod.V2;
+
+/// <seealso href="https://libgpiod.readthedocs.io/en/latest/group__edge__event.html"/>
+internal enum GpiodEdgeEventType
+{
+    RisingEdge = 1,
+    FallingEdge = 2
+}

src/System.Device.Gpio/Interop/Unix/libgpiod/V2/Binding/Enums/GpiodLineBias.cs

@@ -0,0 +1,14 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Device.Gpio.Libgpiod.V2;
+
+/// <seealso href="https://libgpiod.readthedocs.io/en/latest/group__line__defs.html"/>
+internal enum GpiodLineBias
+{
+    AsIs = 1,
+    Unknown = 2,
+    Disabled = 3,
+    PullUp = 4,
+    PullDown = 5
+}

src/System.Device.Gpio/Interop/Unix/libgpiod/V2/Binding/Enums/GpiodLineClock.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Device.Gpio.Libgpiod.V2;
+
+/// <seealso href="https://libgpiod.readthedocs.io/en/latest/group__line__defs.html"/>
+internal enum GpiodLineClock
+{
+    Monotonic = 1,
+    Realtime = 2,
+    Hte = 3
+}

src/System.Device.Gpio/Interop/Unix/libgpiod/V2/Binding/Enums/GpiodLineDirection.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Device.Gpio.Libgpiod.V2;
+
+/// <seealso href="https://libgpiod.readthedocs.io/en/latest/group__line__defs.html"/>
+internal enum GpiodLineDirection
+{
+    AsIs = 1,
+    Input = 2,
+    Output = 3
+}