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Linux: Enumerate HID devices without USB parents #31

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a486964
Linux: Enumerate HID devices without USB parents
Tsuyumi25 Sep 9, 2026
34667a6
Simplify HID_ID parsing
Tsuyumi25 Sep 10, 2026
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48 changes: 45 additions & 3 deletions HidSharp/Platform/Linux/LinuxHidDevice.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ under the License. */
#endregion

using System;
using System.Globalization;
using System.Collections.Generic;
using System.IO;
using System.Runtime.InteropServices;
Expand Down Expand Up @@ -90,6 +91,26 @@ internal static LinuxHidDevice TryCreate(string path)
return d;
}
}

// Devices without USB parents expose their identity through HID udev properties.
IntPtr hidParent = NativeMethodsLibudev.Instance.udev_device_get_parent_with_subsystem_devtype(device, "hid", null);
if (IntPtr.Zero != hidParent)
{
string hidId = NativeMethodsLibudev.Instance.udev_device_get_property_value(hidParent, "HID_ID");

int vid, pid;
if (TryParseHidId(hidId, out vid, out pid))
{
d._vid = vid;
d._pid = pid;
d._version = 0;
d._manufacturer = null;
d._productName = NativeMethodsLibudev.Instance.udev_device_get_property_value(hidParent, "HID_NAME");
d._serialNumber = null;

return d;
}
}
}
}
}
Expand All @@ -108,6 +129,23 @@ internal static LinuxHidDevice TryCreate(string path)
return null;
}

static bool TryParseHidId(string hidId, out int vid, out int pid)
{
vid = 0;
pid = 0;

if (hidId == null) { return false; }

// HID_ID is BUS:VID:PID.
string[] fields = hidId.Split(':');
if (fields.Length != 3) { return false; }

return int.TryParse(fields[1],
NumberStyles.HexNumber, CultureInfo.InvariantCulture, out vid) &&
int.TryParse(fields[2],
NumberStyles.HexNumber, CultureInfo.InvariantCulture, out pid);
}

protected override DeviceStream OpenDeviceDirectly(OpenConfiguration openConfig)
{
RequiresGetInfo();
Expand Down Expand Up @@ -282,10 +320,14 @@ unsafe string GetUsbPath()
{
using (var udev = new SafeUdevHandle(NativeMethodsLibudev.Instance.udev_new()))
{
var handle = NativeMethodsLibudev.Instance.udev_device_new_from_syspath(udev.DangerousGetHandle(), _path);
using (var parent = new SafeUdevDeviceHandle(NativeMethodsLibudev.Instance.udev_device_get_parent_with_subsystem_devtype(handle, "usb", "usb_device")))
var devicePtr = NativeMethodsLibudev.Instance.udev_device_new_from_syspath(udev.DangerousGetHandle(), _path);
using (var device = new SafeUdevDeviceHandle(devicePtr))
{
var parentPtr = parent.DangerousGetHandle();
if (device.IsInvalid) { throw DeviceException.CreateIOException(this, "Failed to find device in udev."); }

var parentPtr = NativeMethodsLibudev.Instance.udev_device_get_parent_with_subsystem_devtype(
device.DangerousGetHandle(), "usb", "usb_device");
if (parentPtr == IntPtr.Zero) { throw DeviceException.CreateIOException(this, "Device has no USB parent."); }

string devNum = NativeMethodsLibudev.Instance.udev_device_get_sysattr_value(parentPtr, "devnum");
string busNum = NativeMethodsLibudev.Instance.udev_device_get_sysattr_value(parentPtr, "busnum");
Expand Down
2 changes: 2 additions & 0 deletions HidSharp/Platform/Linux/NativeMethodsLibudev.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -101,5 +101,7 @@ public abstract string FriendlyName
public abstract string udev_device_get_sysattr_value(IntPtr device, string sysattr);

public abstract int udev_device_get_is_initialized(IntPtr device);

public abstract string udev_device_get_property_value(IntPtr device, string key);
}
}
9 changes: 9 additions & 0 deletions HidSharp/Platform/Linux/NativeMethodsLibudev0.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -215,5 +215,14 @@ public override int udev_device_get_is_initialized(IntPtr device)
{
return native_udev_device_get_is_initialized(device);
}

[DllImport(libudev, EntryPoint = "udev_device_get_property_value")]
[return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))]
static extern string native_udev_device_get_property_value(IntPtr device,
[MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string key);
public override string udev_device_get_property_value(IntPtr device, string key)
{
return native_udev_device_get_property_value(device, key);
}
}
}
9 changes: 9 additions & 0 deletions HidSharp/Platform/Linux/NativeMethodsLibudev1.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -215,5 +215,14 @@ public override int udev_device_get_is_initialized(IntPtr device)
{
return native_udev_device_get_is_initialized(device);
}

[DllImport(libudev, EntryPoint = "udev_device_get_property_value")]
[return: MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))]
static extern string native_udev_device_get_property_value(IntPtr device,
[MarshalAs(UnmanagedType.CustomMarshaler, MarshalTypeRef = typeof(Utf8Marshaler))] string key);
public override string udev_device_get_property_value(IntPtr device, string key)
{
return native_udev_device_get_property_value(device, key);
}
}
}