Re: [PATCH 1/2] joydev: Map ABS_{THROTTLE,GAS,BREAK} to positive values.

I didnt test with games on steam.
I've tested with supertuxkart 0.8.1 and jstest.

Could you give me a hint, why you think that it breaks(?) input detection?

I think SDL2 used evdev, so how should a changed joydev break the
correction? (or do you mean in joydev fallback mode?)
Searching through the SDL code I guess you refer to this:
 http://hg.libsdl.org/SDL/file/a5f8137ccf01/src/joystick/SDL_gamecontroller.c#l133
This really looks like a workaround for this brokeness of the joydev
correction for triggers,
thats why this should be fixed in kernel.

It cant really be inteded to map triggers to -32767-32767, and
consider this API to not brake application that have workarounds for
this.
Or is it?

2013/12/14 Ken Phillis Jr [off-list ref]:

On Wed, Dec 11, 2013 at 2:15 AM, Benjamin Franzke
[off-list ref] wrote:

quoted

Gamepads like XInput devices have triggers with a range from
e.g. 0 to 255.
When the conventional joydev AXES correction/mapping method is used,
the default state 0 (i.e. when the user does not press a button or trigger)
is mapped to -32767 (and 255 to 32767).
You'll get 0 only when pressing the trigger half-way down.
This has several drawbacks:
 - A trigger is not usable at all when configured to have 2 directions
   when there is physically only one.
 - Applications that let the user configure joystick input assignments
   may register the mapped non-zero default state as a press,
   preventing the user from configuring any sensible value.

Traditonal calibration e.g. with jscal does not help to get a usable
experience either, it'll map the default state to -32767 as well.
Only manually editing the calibration data does work currently.

This patch tries to fix this issue by calculating a positive-only range for
the throttle break and gas ABS bits.
Maybe other ABS types need to be added to this scheme as well(?)

Note:
Although joydev is considered obsolete and people are encouraged to just
use evdev, joydev should still be fixed, because
 1. many applications still use it.
 2. userspace already copies the joydev correction code to evdev (e.g. libSDL).

This bug should be fixed here in joydev first, and when we have a good
sensible state, this should be propagated to the application/libraries
that copied the joydev correction code.

Gamepad drivers will need to advertise triggers as THROTTLE,GAS,BREAK instead
of e.g. ABS_{RZ,Z} where phyisically appropriate, to make use of this.

I've considered changing the current joydev correction calculation for all ABS
types, to have only a scaling functionality by default, no translation
(all positive values remain positive, negatives negative and zero remains zero),
so that drivers would need to expose zero-centered ABS values.
It turned out to many drivers would need to be adjusted, which i cant
test.

Signed-off-by: Benjamin Franzke <redacted>

I have serious concerns that this Patch and the Next patch will the
input detection of the triggers on various games powered by SDL2. Have
you tested this against games listed on steam that have full
controller support?