Monday, December 3, 2018

ggkbdd is a generic gaming keyboard daemon

Last week while reviewing a patch I read that some gaming keyboards have two modes - keyboard mode and gaming mode. When in gaming mode, the keys send out pre-recorded macros when pressed. Presumably (I am not a gamer) this is to record keyboard shortcuts to have quicker access to various functionalities. The macros are stored in the hardware and are thus relatively independent of the host system. Pprovided you have access to the custom protocol, which you probably don't when you're on Linux. But I digress.

I reckoned this could be done in software and work with any 5 dollar USB keyboard. A few hours later, I have this working now: ggkbdd. It sits directly above the kernel and waits for key events. Once the 'mode key' is hit, the keyboard will send pre-configured key sequences for the respective keys. Hitting the mode key again (or ESC) switches back to normal mode.

There's a lot of functionality that is missing such as integration with the desktop (probably via DBus), better security (dropping privs, masking the fd to avoid accidental key logging), better system integration (request fds from logind, possibly through the compositor). And error handling, etc. I think the total time on this spent is somewhere between 3 and 4h, and that includes the time to write this blog post and debug the systemd unit autostartup. There are likely other projects that solve it the same way, or at least in a similar manner. I didn't check.

This was done as proof-of-concept and

  • I don't know if it's useful and if so, what the use-cases are
  • I don't know if I will have any time to fix things on this
  • I don't know if other (better developed) projects already occupy that space
In the grand glorious future and provided this is indeed something generally useful, this would need compositor integration. Not sure we'll ever get to that point. Meanwhile, consider this a code drop for a proof-of-concept and expect that you'll have to fix any bugs yourself.