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linux: Improve gamepad mapping heuristic to accept Android conventions 

This heuristic for gamepads without a more specific mapping already
tried two incompatible conventions for handling triggers: the Linux
Gamepad Specification uses hat switch 2 for the triggers (for whatever
reason), but the de facto standard set by the drivers for older Xbox
and Playstation controllers represents each trigger as the Z-axis of
the nearest analog stick.

Android documentation encourages Bluetooth gamepad manufacturers to use
a third incompatible convention where the left and right triggers are
represented as the brake and gas pedals of a driving simulator
controller. The Android convention also changes the representation of
the right stick: instead of using X and Y rotation as a second pair
of axes, Android uses Z position as a second horizontal axis, and
Z rotation as a second vertical axis.

Try to cope gracefully with all of these. This will hopefully resolve
the issue described in #5406 (when using unpatched kernels).

Signed-off-by: Simon McVittie <smcv@collabora.com>
main
Simon McVittie 2023-06-09 13:24:21 +01:00 committed by Sam Lantinga
parent c4d49fadd4
commit cf1dc66e2c
1 changed files with 52 additions and 0 deletions
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52
src/joystick/linux/SDL_sysjoystick.c
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@ -1608,6 +1608,8 @@ static void LINUX_JoystickQuit(void)
/*
This is based on the Linux Gamepad Specification
available at: https://www.kernel.org/doc/html/v4.15/input/gamepad.html
and the Android gamepad documentation,
https://developer.android.com/develop/ui/views/touch-and-input/game-controllers/controller-input
*/
static SDL_bool LINUX_JoystickGetGamepadMapping(int device_index, SDL_GamepadMapping *out)
{
@ -1828,14 +1830,35 @@ static SDL_bool LINUX_JoystickGetGamepadMapping(int device_index, SDL_GamepadMap
/* Prefer analog triggers, but settle for digital hat or buttons. */
mapped = 0;
/* Unfortunately there are several conventions for how analog triggers
* are represented as absolute axes:
*
* - Linux Gamepad Specification:
* LT = ABS_HAT2Y, RT = ABS_HAT2X
* - Android (and therefore many Bluetooth controllers):
* LT = ABS_BRAKE, RT = ABS_GAS
* - De facto standard for older Xbox and Playstation controllers:
* LT = ABS_Z, RT = ABS_RZ
*
* We try each one in turn. */
if (joystick->hwdata->has_abs[ABS_HAT2Y]) {
/* Linux Gamepad Specification */
out->lefttrigger.kind = EMappingKind_Axis;
out->lefttrigger.target = joystick->hwdata->abs_map[ABS_HAT2Y];
mapped |= MAPPED_TRIGGER_LEFT;
#ifdef DEBUG_GAMEPAD_MAPPING
SDL_Log("Mapped LEFTTRIGGER to axis %d (ABS_HAT2Y)", out->lefttrigger.target);
#endif
} else if (joystick->hwdata->has_abs[ABS_BRAKE]) {
/* Android convention */
out->lefttrigger.kind = EMappingKind_Axis;
out->lefttrigger.target = joystick->hwdata->abs_map[ABS_BRAKE];
mapped |= MAPPED_TRIGGER_LEFT;
#ifdef DEBUG_GAMEPAD_MAPPING
SDL_Log("Mapped LEFTTRIGGER to axis %d (ABS_BRAKE)", out->lefttrigger.target);
#endif
} else if (joystick->hwdata->has_abs[ABS_Z]) {
/* De facto standard for Xbox 360 and Playstation gamepads */
out->lefttrigger.kind = EMappingKind_Axis;
out->lefttrigger.target = joystick->hwdata->abs_map[ABS_Z];
mapped |= MAPPED_TRIGGER_LEFT;
@ -1845,13 +1868,23 @@ static SDL_bool LINUX_JoystickGetGamepadMapping(int device_index, SDL_GamepadMap
}
if (joystick->hwdata->has_abs[ABS_HAT2X]) {
/* Linux Gamepad Specification */
out->righttrigger.kind = EMappingKind_Axis;
out->righttrigger.target = joystick->hwdata->abs_map[ABS_HAT2X];
mapped |= MAPPED_TRIGGER_RIGHT;
#ifdef DEBUG_GAMEPAD_MAPPING
SDL_Log("Mapped RIGHTTRIGGER to axis %d (ABS_HAT2X)", out->righttrigger.target);
#endif
} else if (joystick->hwdata->has_abs[ABS_GAS]) {
/* Android convention */
out->righttrigger.kind = EMappingKind_Axis;
out->righttrigger.target = joystick->hwdata->abs_map[ABS_GAS];
mapped |= MAPPED_TRIGGER_RIGHT;
#ifdef DEBUG_GAMEPAD_MAPPING
SDL_Log("Mapped RIGHTTRIGGER to axis %d (ABS_GAS)", out->righttrigger.target);
#endif
} else if (joystick->hwdata->has_abs[ABS_RZ]) {
/* De facto standard for Xbox 360 and Playstation gamepads */
out->righttrigger.kind = EMappingKind_Axis;
out->righttrigger.target = joystick->hwdata->abs_map[ABS_RZ];
mapped |= MAPPED_TRIGGER_RIGHT;
@ -1972,7 +2005,16 @@ static SDL_bool LINUX_JoystickGetGamepadMapping(int device_index, SDL_GamepadMap
#endif
}
/* The Linux Gamepad Specification uses the RX and RY axes,
* originally intended to represent X and Y rotation, as a second
* joystick. This is common for USB gamepads, and also many Bluetooth
* gamepads, particularly older ones.
*
* The Android mapping convention used by many Bluetooth controllers
* instead uses the Z axis as a secondary X axis, and the RZ axis as
* a secondary Y axis. */
if (joystick->hwdata->has_abs[ABS_RX] && joystick->hwdata->has_abs[ABS_RY]) {
/* Linux Gamepad Specification, Xbox 360, Playstation etc. */
out->rightx.kind = EMappingKind_Axis;
out->righty.kind = EMappingKind_Axis;
out->rightx.target = joystick->hwdata->abs_map[ABS_RX];
@ -1980,6 +2022,16 @@ static SDL_bool LINUX_JoystickGetGamepadMapping(int device_index, SDL_GamepadMap
#ifdef DEBUG_GAMEPAD_MAPPING
SDL_Log("Mapped RIGHTX to axis %d (ABS_RX)", out->rightx.target);
SDL_Log("Mapped RIGHTY to axis %d (ABS_RY)", out->righty.target);
#endif
} else if (joystick->hwdata->has_abs[ABS_Z] && joystick->hwdata->has_abs[ABS_RZ]) {
/* Android convention */
out->rightx.kind = EMappingKind_Axis;
out->righty.kind = EMappingKind_Axis;
out->rightx.target = joystick->hwdata->abs_map[ABS_Z];
out->righty.target = joystick->hwdata->abs_map[ABS_RZ];
#ifdef DEBUG_GAMEPAD_MAPPING
SDL_Log("Mapped RIGHTX to axis %d (ABS_Z)", out->rightx.target);
SDL_Log("Mapped RIGHTY to axis %d (ABS_RZ)", out->righty.target);
#endif
}