Open Source Summit Europe 2024

Ever since the GPIO character device was introduced as a proposed uAPI replacement for the deprecated sysfs interface, users have been pointing to the lack of persistence of GPIO state (as in: once the user-space process closes the file descriptor associated with a set of requested lines, their state is no longer defined - in practice: it's driver dependent) as the main issue with the new approach and a significant blocker in porting code from sysfs to libgpiod. Two solutions have been proposed: making the GPIO state persistent in the kernel or providing a centralized authority for controlling GPIOs from user-space. For various reasons the former has been rejected which led to the development of gpio-manager: a user-space daemon built on top of libgpiod that exposes an API to authorized clients and controls GPIOs on their behalf. This talk will present the features of the daemon, the DBus API it implements and the companion command-line client - gpiocli - which aims at allowing straightforward porting of sysfs-based scripts to the new interface.