Multiple defcfg linux-dev

[br-lemes]

I use two of these 6x4 keypad as a split keyboard. As they are two independent keyboards, normally I can't setup layers which works across the "halves" (a key in one keypad which activates a layer in the other one). To solve this I currently use evsieve to fake one device out of these two. This way:

# evsieve --input /dev/input/by-id/usb-BlackC_Sayobot.cn_L-event-kbd grab --input /dev/input/by-id/usb-BlackC_Sayobot.cn_R-event-kbd grab --output create-link=/dev/input/by-id/sayo

It would be nice if kanata could use multiple devices this way out of the box.

[jtroo]

That's a cool use case, thanks for sharing it! 👍

[jtroo]

You've probably found this already, but for reference, the input reading is done in:
https://github.com/jtroo/kanata/blob/main/src/oskbd/linux.rs

Currently, the event loop does blocking calls to fetch_events for a single device, so would need to rearchitect the input event handling to be able to handle multiple devices. It would be good to dig into evsieve's source as inspiration for how they do it.

---

Edit:

Browsing through evsieve's source, it uses C style code using epoll and raw file descriptors. Quite efficient, but a lot more complicated than what kanata's doing.

[jtroo]

I've added a kanata-evsieve crate exposing the evsieve functionality as a library. Not sure yet if using it is a viable strategy, but seems like it should work out okay.

[jtroo]

@br-lemes please test the code in the new PR at your leisure. I haven't actually tested it on multiple keyboards myself since I don't have a convenient way to do so, but I think it should work.

Config change:

  ;; If you want to read from multiple devices, separate them by `:`.
  ;; linux-dev /dev/input/<dev1>:/dev/input/<dev2>

[br-lemes]

Yes, it works. I'm typing using the PR version right now!

It's great!