Input devices

PS/2 keyboard

The primary input: scancode set 1 -> ASCII in the kernel (drivers/input/driver_input_keyboard.c), feeding the line editor directly. Always present in QEMU.

COM1 serial

screen_serial_in.c - serial RX feeds the same keyboard queue, so -serial mon:stdio gives you a full console.

USB HID

driver_usb_hid.c - keyboards and mice through any host controller; usb_kbd_test / usb_mouse_test gate them.

I2C HID + touchpads

driver_input_i2chid.c + the touchpad stack: i2cdetect finds the device, touchpad/touchtest exercise it (real hardware; QEMU has no model).

The contract

All input sources converge on the shell/TUI input queues - adding a source means feeding the same queue, not new input paths.