Summary
In this chapter, we introduced the pin control framework and described its interaction with the GPIO subsystem. We learned how to deal with GPIOs, either as a controller or consumer, from both the kernel and the user space. Though the legacy integer-based interface is deprecated, it was introduced because it is still widely used. Additionally, we introduced some advanced topics such as IRQ chip support in the GPIO chip and the mapping of GPIOs to IRQs. We ended this chapter by learning how to deal with GPIOs from the user space, by writing C code or by using dedicated command-line tools provided by the standard Linux GPIO library, libgpiod.
In the next chapter, we deal with input devices, which can be implemented using GPIOs.
