How does CE-RH2 work?

[glu]

How does Zaurus remote actually work? I tried reading driver sources, but these seem to read PXA GPIO chips, which I guess means that some chip already processes remote input and passes it to SoC? Is it using some well known standard for this? Are there any known replacements that work as CE-RH2 is very hard to find in 2024.

[greguu]

It's GPIO driven, yes. There was a patch for 2.6 kernel series, but it never went upstream as far as I know.
It could be ported to 5.4 stable branch with a patch I guess ?
https://git.yoctoproject.org/poky/plain/meta/packages/linux/linux-rp-2.6.26/sharpsl-rc-r1.patch?h=green
From what I could gather, the above patch detects if the remote is inserted or not, then certain GPIO events are translated to keyboard events for volume up /down etc.
It's not a standard, its a custom thing. You could build a custom remote based on this...

The Zaurus also have IR support for remotes, but you would need line of sight, so not very pocket friendly.
The kernel LIRC support had changed some while back. I have not used it for a while. With 3.x kernel it still worked and you could even tether via IR from a Nokia phone...