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Bug 4789

Summary: Linux accelerometers no longer available as joysticks
Product: SDL Reporter: Daniel Drake <dan>
Component: joystickAssignee: Sam Lantinga <slouken>
Status: RESOLVED FIXED QA Contact: Sam Lantinga <slouken>
Severity: normal    
Priority: P2    
Version: HG 2.1   
Hardware: x86_64   
OS: Linux   
Attachments: Support SDL_HINT_ACCELEROMETER_AS_JOYSTICK on Linux

Description Daniel Drake 2019-09-05 05:32:00 UTC 
Created attachment 3952 [details]
Support SDL_HINT_ACCELEROMETER_AS_JOYSTICK on Linux

A long time ago, it was possible to play neverball on Linux using the accelerometer found in HP laptops.

The kernel exposes the accelerometer as a joystick (/dev/input/jsX) as well as an evdev device (/dev/input/eventX). I guess it worked fine when SDL was using the js interface, but then stopped working here: http://hg.libsdl.org/SDL/rev/fdaeea9e7567

Looking at current code which uses udev to discover joysticks, it looks for the udev tag ID_INPUT_JOYSTICK.

However udev's internal input_id logic specifically tags accelerometers as ID_INPUT_ACCELEROMETER and nothing else.

This looks like a good fit for SDL_HINT_ACCELEROMETER_AS_JOYSTICK.
Comment 1 Sam Lantinga 2019-09-06 15:43:15 UTC 
Looks good to me, thanks!
https://hg.libsdl.org/SDL/rev/211e1b06ec47