Linux – Kernel debugging

If you don't have a USB headset your headset is typically handled by your normal audio driver, e.g. if you plug your headset in the driver will typically mute the speakers and use the headset output instead. Audio drivers nowadays are typically Alsa drivers and can be found in the sound directory of the Linux kernel.

If you have a USB headset it will be a dedicated soundcard and you would need to modify the driver for your specific USB headset.

To determine the specific driver for your soundcard use

lshw -v

and have a look at the Kernel driver in use: snd_hda_intel line or use lsmod to list your modules and determine your audio driver.

The keypress generates an interrupt, just like you figured out. The interrupt is processed by an interrupt handler; which handler depends on the type of hardware, e.g. USB keyboard or PS/2 keyboard. The interrupt handler reads the key code from the hardware and buffers it. From the buffer the character is picked up by the tty driver, which, in the case of Ctrl-C recognizes it as the interrupt character and sends a SIGINT to the foreground process group of the terminal. See n_tty.c.

Note that the tty driver is only involved in "terminal"-type (command line) interfaces, like the Linux console, serial terminals (/dev/ttyS*), and pseudo ttys. GUI systems (X11, Wayland implementations) handle input devices differently.