Compound Interest - Dealing with Two Decades of Technical Debt in Embedded Linux

Explore the evolution and challenges of the GPIO subsystem in the Linux kernel over the past two decades. Delve into the complexities of managing technical debt in embedded Linux, focusing on the GPIO driver abstraction layer. Learn about the subsystem's growth, integration with the driver model, and acquisition of new features such as device-tree and ACPI support. Examine the impact of ARM fragmentation on the codebase and the resulting maintenance challenges. Understand the current state of the subsystem, including its dual in-kernel APIs, uAPI variants, and intricate connections to pinctrl and interrupt subsystems. Discover ongoing efforts to improve serialization, enhance hot-pluggability, and reduce API abuse across the kernel tree while carefully navigating legacy user requirements.