Explore the intricacies of the GPIO subsystem in this comprehensive 51-minute talk by Linux kernel developer Linus Walleij. Delve into recent changes, including GPIO descriptor refactoring and new support for open drain. Learn about hardware descriptions in device tree and ACPI, and discover the new userspace character device ABI for GPIO chips. Understand how makers and industrial control clients can benefit from these developments. Gain insights into the subsystem's future direction, covering topics such as GPIO ships, pin control, IRQ domain, GPIO expanders, and userspace GPIO. Examine random drivers, GPIO line names, and techniques for reading line values and manipulating multiple lines. Perfect for engineers and makers looking to deepen their understanding of GPIO in Linux systems.