How do I set analog sensitivity (and deadzone) per-controller (and per-axis or per-stick)

[geekley]

I'd like to properly contribute a controller configuration for a generic made-in-china GameCube adapter I bought.
It's brand-less and has no site info in the manual/package, it only has a model number. But anyways.

The GameCube input for the analog sticks is in octagon-shape (not square) and it doesn't go all the way from 0.0 to 1.0.
It's more like 0 ~ 0.75 for left stick and 0 ~ 0.7 for C-stick. Or, according to Dolphin, the exact/default values for a GameCube controller seem to be 79.37% for main stick and 72.21% for C-stick (I assume they must have done some research to come up with such precise values).
The analog L and R are even weirder, going, in my tests, from about -0.75 ~ 0.85 at the button press (then it keeps going to about 0.9 if you press harder.

So I have to set RetroArch analog sensitivity to about 1.4 to get an acceptable result. But this setting is global.

1. How do I set analog sensitivity in the controller configuration file?
   Even better if it can be set per-axis or per 2D vector.
2. Same question for deadzone.

I didn't find anything in docs regarding these. Is it not implemented? It makes no sense that analog sensitivity and deadzone settings would be global; that's a controller (or rather, axis) property.

3. Is there a way to make analog L and R account for negative values (and should I)? Dolphin makes a distinction between "axis" and "full axis"; I don't know how that works in RetroPad config, I just see that there's + and - for each axis. Values like input_l2_plus_axis and input_l2_minus_axis don't seem to work, only input_l2_axis, which I'm setting to the + of the axis. I'm not sure how I can confirm whether it's getting the full input or just the positive part.

[offalynne]

How do I set analog sensitivity in the controller configuration file?

You can not

0 ~ 0.75

This is "normal" for GC in many contexts. No fix for now except the emulator setting as you mentioned. If you want per-device axis settings or a field for axis range in the autoconfig format, you'll have to take the issue upstream to the RA frontend project.

[geekley]

Ah, it seems there is already an issue: libretro/RetroArch#14400
I'll update it with info from here.