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Fixed bug 4583 - PollAllValues appears to use an incorrect index for all axes above 0x18

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Noam Preil

In src/joystick/linux/SDL_sysjoystick.c:

The ConfigJoystick function's axes detection starts with a for loop using an index i for Linux's axes names. When i gets to ABS_HAT0X, it's set to ABS_HAT3Y and a continue statement appears, to skip the hats. This makes sense, as SDL handles hats separately from axes.

However, in PollAllValues, *two* indices are used: a and b. Both start out the same, and remain so until the hats are reached. At that point, a becomes identical to the i from ConfigJoystick's loop, but b is equal to a - (ABS_HAT3Y - ABS_HAT0X), or a - 8.

While all the joystick->hwdata->abs_* structures in ConfigJoystick used i - which would here be a - as both the index and the ioctl argument, PollAllValues uses b for the structure index and a as the ioctl argument.

It would appear, however, that no joystick HAS such axes, and that the b index is entirely unnecessary.

I tested three separate joysticks, and while that was far from a complete listing, I was unable to find a joystick with an axis above 0x08.
This commit is contained in:
Sam Lantinga 2019-06-08 14:40:27 -07:00
parent 59483c6446
commit 56b7f4cf31
1 changed files with 14 additions and 24 deletions
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38
src/joystick/linux/SDL_sysjoystick.c
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@ -818,36 +818,26 @@ static SDL_INLINE void
PollAllValues(SDL_Joystick * joystick)
{
struct input_absinfo absinfo;
int a, b = 0;
int i;
/* Poll all axis */
for (a = ABS_X; b < ABS_MAX; a++) {
switch (a) {
case ABS_HAT0X:
case ABS_HAT0Y:
case ABS_HAT1X:
case ABS_HAT1Y:
case ABS_HAT2X:
case ABS_HAT2Y:
case ABS_HAT3X:
case ABS_HAT3Y:
/* ingore hats */
break;
default:
if (joystick->hwdata->abs_correct[b].used) {
if (ioctl(joystick->hwdata->fd, EVIOCGABS(a), &absinfo) >= 0) {
absinfo.value = AxisCorrect(joystick, b, absinfo.value);
for (i = ABS_X; i < ABS_MAX; i++) {
if (i == ABS_HAT0X) {
i = ABS_HAT3Y;
continue;
}
if (joystick->hwdata->abs_correct[i].used) {
if (ioctl(joystick->hwdata->fd, EVIOCGABS(i), &absinfo) >= 0) {
absinfo.value = AxisCorrect(joystick, i, absinfo.value);
#ifdef DEBUG_INPUT_EVENTS
printf("Joystick : Re-read Axis %d (%d) val= %d\n",
joystick->hwdata->abs_map[b], a, absinfo.value);
printf("Joystick : Re-read Axis %d (%d) val= %d\n",
joystick->hwdata->abs_map[i], i, absinfo.value);
#endif
SDL_PrivateJoystickAxis(joystick,
joystick->hwdata->abs_map[b],
absinfo.value);
}
SDL_PrivateJoystickAxis(joystick,
joystick->hwdata->abs_map[i],
absinfo.value);
}
b++;
}
}
}