Add a simple PS/2 mouse device.

It's not hooked up to anything just yet, but it does read movement deltas.

Kernel/Makefile

@@ -25,6 +25,7 @@ KERNEL_OBJS = \
        ELFImage.o \
        ELFLoader.o \
        KSyms.o \
+       PS2MouseDevice.o \
        WindowComposer.o
 
 VFS_OBJS = \

Kernel/PS2MouseDevice.cpp

@@ -0,0 +1,113 @@
+#include "PS2MouseDevice.h"
+#include "IO.h"
+
+PS2MouseDevice::PS2MouseDevice()
+    : IRQHandler(12)
+    , CharacterDevice(10, 1)
+{
+    initialize();
+}
+
+PS2MouseDevice::~PS2MouseDevice()
+{
+}
+
+void PS2MouseDevice::handle_irq()
+{
+    m_data[m_data_state] = IO::in8(0x60);
+    switch (m_data_state) {
+    case 0:
+    case 1:
+        ++m_data_state;
+        break;
+    case 2:
+        m_data_state = 0;
+        dbgprintf("PS2Mouse: %d, %d\n", m_data[1], m_data[2]);
+        break;
+    }
+}
+
+void PS2MouseDevice::wait_then_write(byte port, byte data)
+{
+    prepare_for_output();
+    IO::out8(port, data);
+}
+
+byte PS2MouseDevice::wait_then_read(byte port)
+{
+    prepare_for_input();
+    return IO::in8(port);
+}
+
+void PS2MouseDevice::initialize()
+{
+    // Enable PS aux port
+    wait_then_write(0x64, 0xa8);
+
+    // Enable interrupts
+    wait_then_write(0x64, 0x20);
+
+    byte status = wait_then_read(0x60) | 2;
+    wait_then_write(0x64, 0x60);
+    wait_then_write(0x60, status);
+
+    // Set default settings.
+    mouse_write(0xf6);
+    byte ack1 = mouse_read();
+    ASSERT(ack1 == 0xfa);
+
+    // Enable.
+    mouse_write(0xf4);
+    byte ack2 = mouse_read();
+    ASSERT(ack2 == 0xfa);
+
+    enable_irq();
+}
+
+void PS2MouseDevice::prepare_for_input()
+{
+    for (;;) {
+        if (IO::in8(0x64) & 1)
+            return;
+    }
+}
+
+void PS2MouseDevice::prepare_for_output()
+{
+    for (;;) {
+        if (!(IO::in8(0x64) & 2))
+            return;
+    }
+}
+
+void PS2MouseDevice::mouse_write(byte data)
+{
+    prepare_for_output();
+    IO::out8(0x64, 0xd4);
+    prepare_for_output();
+    IO::out8(0x60, data);
+}
+
+byte PS2MouseDevice::mouse_read()
+{
+    prepare_for_input();
+    return IO::in8(0x60);
+}
+
+bool PS2MouseDevice::has_data_available_for_reading() const
+{
+    ASSERT_NOT_REACHED();
+    return false;
+}
+
+ssize_t PS2MouseDevice::read(byte* buffer, size_t buffer_size)
+{
+    ASSERT_NOT_REACHED();
+    return 0;
+}
+
+ssize_t PS2MouseDevice::write(const byte *buffer, size_t buffer_size)
+{
+    ASSERT_NOT_REACHED();
+    return 0;
+}

Kernel/PS2MouseDevice.h

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <VirtualFileSystem/CharacterDevice.h>
+#include "IRQHandler.h"
+
+class PS2MouseDevice final : public IRQHandler, public CharacterDevice {
+public:
+    PS2MouseDevice();
+    virtual ~PS2MouseDevice() override;
+
+private:
+    virtual bool has_data_available_for_reading() const override;
+    virtual ssize_t read(byte* buffer, size_t buffer_size) override;
+    virtual ssize_t write(const byte* buffer, size_t buffer_size) override;
+
+    virtual void handle_irq() override;
+
+    void initialize();
+    void prepare_for_input();
+    void prepare_for_output();
+    void mouse_write(byte);
+    byte mouse_read();
+    void wait_then_write(byte port, byte data);
+    byte wait_then_read(byte port);
+
+    byte m_data_state { 0 };
+    signed_byte m_data[3];
+};

Kernel/init.cpp

@@ -20,6 +20,7 @@
 #include "RTC.h"
 #include "VirtualConsole.h"
 #include "Scheduler.h"
+#include "PS2MouseDevice.h"
 
 #define SPAWN_MULTIPLE_SHELLS
 //#define STRESS_TEST_SPAWNING
@@ -31,6 +32,7 @@ VirtualConsole* tty1;
 VirtualConsole* tty2;
 VirtualConsole* tty3;
 Keyboard* keyboard;
+PS2MouseDevice* ps2mouse;
 
 #ifdef STRESS_TEST_SPAWNING
 static void spawn_stress() NORETURN;
@@ -71,7 +73,7 @@ static void init_stage2()
     vfs->register_character_device(*dev_random);
 
     vfs->register_character_device(*keyboard);
-
+    vfs->register_character_device(*ps2mouse);
     vfs->register_character_device(*tty0);
     vfs->register_character_device(*tty1);
     vfs->register_character_device(*tty2);
@@ -125,6 +127,7 @@ void init()
     idt_init();
 
     keyboard = new Keyboard;
+    ps2mouse = new PS2MouseDevice;
 
     VirtualConsole::initialize();
     tty0 = new VirtualConsole(0, VirtualConsole::AdoptCurrentVGABuffer);