Kernel: Fix PS/2 scancode set detection logic

If we cannot determine current scancode set because either the keyboard
does not respond or responds with bogus value, assume scancode set 1 and
mark the scancode set as uncertain. If we receive the byte 0xF0 while
having the uncertain flag set, swap to scancode set 2. 0xF0 is unused in
scancode set 1 but indicates key release in scancode set 2, so it will
be sent after every key press.

kernel/include/kernel/Input/PS2/Keyboard.h

@@ -36,6 +36,7 @@ namespace Kernel::Input
 		uint8_t m_byte_index { 0 };
 		bool m_basic { false };
 
+		bool m_scancode_set_uncertain { false };
 		uint8_t m_scancode_set { 0xFF };
 		uint16_t m_modifiers { 0 };
 

kernel/kernel/Input/PS2/Keyboard.cpp

@@ -53,8 +53,9 @@ namespace Kernel::Input
 
 		if (command_data[0] == Command::CONFIG_SCANCODE_SET && m_scancode_set >= 0xFE)
 		{
-			dwarnln("Could not detect scancode set, assuming 2");
+			dwarnln("Could not detect scancode set, assuming 1");
-			m_scancode_set = 2;
+			m_scancode_set_uncertain = true;
+			m_scancode_set = 1;
 			m_keymap.initialize(m_scancode_set);
 			append_command_queue(PS2::DeviceCommand::ENABLE_SCANNING, 0);
 		}
@@ -89,6 +90,7 @@ namespace Kernel::Input
 			else
 			{
 				dwarnln("Could not detect scancode set, assuming 1");
+				m_scancode_set_uncertain = true;
 				m_scancode_set = 1;
 			}
 			m_keymap.initialize(m_scancode_set);
@@ -103,6 +105,17 @@ namespace Kernel::Input
 			return;
 		}
 
+		// If we could not detect scancode set, we assume it to be 1
+		// If we get byte 0xF0 which is indicates release in scancode set 2
+		// and nothing in scancode set 1, switch to scancode set 2
+		if (m_scancode_set_uncertain && byte == 0xF0)
+		{
+			dprintln("Switching to scancode set 2");
+			m_scancode_set_uncertain = false;
+			m_scancode_set = 2;
+			m_keymap.initialize(m_scancode_set);
+		}
+
 		m_byte_buffer[m_byte_index++] = byte;
 		if (byte == 0xE0)
 			return;