Kernel/HID: Introduce the all-mice device

This device will be used by userspace to read mouse packets from all
mouse devices that are attached to the machine.

This change is a preparation before we can enable seamless hotplug
capabilities in WindowServer for mouse devices, without any major change
on the userspace side.

Kernel/Devices/HID/AllMiceDevice.cpp

@@ -0,0 +1,57 @@
+/*
+ * Copyright (c) 2023, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <Kernel/Devices/DeviceManagement.h>
+#include <Kernel/Devices/HID/AllMiceDevice.h>
+#include <Kernel/Devices/HID/Management.h>
+
+namespace Kernel {
+
+NonnullRefPtr<AllMiceDevice> AllMiceDevice::must_create()
+{
+    return *MUST(DeviceManagement::try_create_device<AllMiceDevice>());
+}
+
+AllMiceDevice::AllMiceDevice()
+    : CharacterDevice(12, 0)
+{
+}
+
+void AllMiceDevice::enqueue_mouse_packet(MousePacket packet)
+{
+    {
+        SpinlockLocker lock(m_queue_lock);
+        m_queue.enqueue(packet);
+    }
+    evaluate_block_conditions();
+}
+
+AllMiceDevice::~AllMiceDevice() = default;
+
+bool AllMiceDevice::can_read(OpenFileDescription const&, u64) const
+{
+    SpinlockLocker lock(m_queue_lock);
+    return !m_queue.is_empty();
+}
+
+ErrorOr<size_t> AllMiceDevice::read(OpenFileDescription&, u64, UserOrKernelBuffer& buffer, size_t size)
+{
+    VERIFY(size > 0);
+    size_t nread = 0;
+    size_t remaining_space_in_buffer = static_cast<size_t>(size) - nread;
+    SpinlockLocker lock(m_queue_lock);
+    while (!m_queue.is_empty() && remaining_space_in_buffer) {
+        auto packet = m_queue.dequeue();
+
+        size_t bytes_read_from_packet = min(remaining_space_in_buffer, sizeof(MousePacket));
+        TRY(buffer.write(&packet, nread, bytes_read_from_packet));
+        nread += bytes_read_from_packet;
+        remaining_space_in_buffer -= bytes_read_from_packet;
+    }
+    return nread;
+}
+
+}