This page describes what libinput is, but more importantly it also describes what libinput is not.
libinput is an input stack to be used by those applications that need full input device processing by commonly used input devices. That includes mice, keyboards, touchpads, touchscreens and graphics tablets. libinput handles device-specific quirks and provides an easy-to-use interface to receive events from devices.
libinput is designed to handle all input devices available on a system. It is possible to limit the devices that employ libinput. For example, the use of xf86-input-libinput depends on xorg.conf snippets for specific devices. But libinput works best if it handles all input devices as this allows for cross-device monitoring of events and smarter handling of features that affect multiple devices.
libinput restricts device-specific features to applicable devices only. Devices with specific hardware properties may expose extra features, but these features are not made available on other devices, even where it may be possible to do so. One example for this are the top software buttons on the touchpad in the Lenovo T440 and similar devices. While there may be use-cases for providing top software buttons on other devices, libinput does not do so.
libinput is not a project to support experimental devices. Unless a device is commonly available off-the-shelf, libinput will not support this device. libinput can serve as a useful base for getting experimental devices enabled and reduce the amount of boilerplate required. But such support will not land in libinput master until the devices are commonly available.
libinput is not a box of legos. It does not provide the pieces to assemble a selection of features. Many features can be disabled through configuration options, but some features are hardcoded or hardcoded on some devices. This usually matches the intended use of the device. There are plenty of use-cases to provide out-of-the-ordinary features, but libinput is not the place to support these.
libinput is not a showcase for features. There are a lot of potential features that could be provided on input devices. But unless they have common usage, libinput is not the place to implement them. Every feature multiplies the maintenance effort, any feature that is provided but unused is a net drain on the already sparse developer resources libinput has available.
libinput is boring. It does not intend to break new grounds on how devices are handled. Instead, it takes best practice and the common use-cases and provides it in an easy-to-consume package for compositors or other processes that need those interactions typically expected by users.
