These simple user-space drivers support using certain homemade, repurposed, or commercial devices as MIDI controllers on Linux, even though the devices themselves are not capable of generating MIDI messages; this does not include things like MIDI-over-serial or PIC based projects, which are true MIDI devices.
Reasons for using this software include: achieving MIDI entry on machines without MIDI ports, reusing old hardware, pure frugality, and fun.
The high retail price of even the simplest MIDI keyboards is totally incongruent with the level of technology involved, or the quality of the construction. The average TV remote control or toy transistor radio represents orders of magnitude more sophistication at a tiny fraction of the price. Musical keyboards that don't speak MIDI (toys or antiques) can be found at little or no cost and adapted for use with Linux. Mice can be used as foot controllers/pedal boards, old analog joysticks as pitch/mod wheels. Clunky, clicky QWERTY keyboards as musical keyboards and so on. Once connected to this software these devices will be indistinguishable from real MIDI hardware. If your computer has a MIDI port, you can even route the messages out to control real synth modules or be recorded in your favorite sequencer on your Atari ST.
I wrote this software for myself. That is to say, I own and use all the devices it supports. Your needs may differ substantially. Feel free to adapt the code as necessary. It is assumed that users have a working knowledge of MIDI/audio under Linux and can setup and route through the ALSA Sequencer interface.
Each of the drivers utilizes the Linux input event interface and monopolizes its attached device, except for lsmi-monterey, which filters out musical events and passes textual key-presses on to applications. There is no dependence on X, necessity for window focus, etc.
For specific information, see the comments at the heads of the respective source files.
Projects shouldn't be dwarfed by the autoconf scripts required to build them. Therefore, LSMI is distributed with a very simple makefile; you'll have to ensure that you have the appropriate kernel and alsa-lib headers installed before building.
Distribution specific init scripts are not included. The drivers may be started from init, your .bashrc, by QJackCtl, etc. In order to be run by a non-root user the drivers must have access to the device files in /dev/input. This may be accomplished by adding a group 'input', adding desired users to this group, and configuring udev to assign the appropriate ownership to files in /dev/input. It should be resonably safe to run the drivers as root, however.
Likewise, for realtime scheduling you must add lines to /etc/security/limits.conf to allow a certain user or group to change rt priorities (this is probably already the case on a machine set up for Jack.)