Hi List,
may I ask for some (other) comments that actually help fix this bug?
Some vague concerns dont really help.
Thanks, Ben
2013/12/11 Benjamin Franzke <benjaminfranzke@xxxxxxxxxxxxxx>:
> 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 <benjaminfranzke@xxxxxxxxxxxxxx>
> ---
> drivers/input/joydev.c | 59 +++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 44 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/input/joydev.c b/drivers/input/joydev.c
> index f362883..8352bee 100644
> --- a/drivers/input/joydev.c
> +++ b/drivers/input/joydev.c
> @@ -761,11 +761,50 @@ static bool joydev_match(struct input_handler *handler, struct input_dev *dev)
> return true;
> }
>
> +static void joydev_calculate_correction(struct input_dev *dev, __u8 abs,
> + struct js_corr *corr)
> +{
> + int t;
> +
> + corr->type = JS_CORR_BROKEN;
> + corr->prec = input_abs_get_fuzz(dev, abs);
> +
> + switch (abs) {
> + /* Map [min - max] => [0 - 32767]. */
> + case ABS_THROTTLE:
> + case ABS_GAS:
> + case ABS_BRAKE:
> + corr->coef[0] = input_abs_get_min(dev, abs);
> + corr->coef[1] = corr->coef[0] + input_abs_get_flat(dev, abs);
> + corr->coef[2] = 0;
> +
> + t = input_abs_get_max(dev, abs) - input_abs_get_min(dev, abs)
> + - input_abs_get_flat(dev, abs);
> + if (t)
> + corr->coef[3] = (1 << 29) / t;
> + break;
> + /* Map [min - max] => [-32768 - 32767]. */
> + default:
> + t = (input_abs_get_max(dev, abs) +
> + input_abs_get_min(dev, abs)) / 2;
> + corr->coef[0] = t - input_abs_get_flat(dev, abs);
> + corr->coef[1] = t + input_abs_get_flat(dev, abs);
> + t = (input_abs_get_max(dev, abs) -
> + input_abs_get_min(dev, abs)) / 2
> + - 2 * input_abs_get_flat(dev, abs);
> + if (t) {
> + corr->coef[2] = (1 << 29) / t;
> + corr->coef[3] = (1 << 29) / t;
> + }
> + break;
> + }
> +}
> +
> static int joydev_connect(struct input_handler *handler, struct input_dev *dev,
> const struct input_device_id *id)
> {
> struct joydev *joydev;
> - int i, j, t, minor, dev_no;
> + int i, j, minor, dev_no;
> int error;
>
> minor = input_get_new_minor(JOYDEV_MINOR_BASE, JOYDEV_MINORS, true);
> @@ -826,23 +865,13 @@ static int joydev_connect(struct input_handler *handler, struct input_dev *dev,
> joydev->abs[i] = input_abs_get_val(dev, j);
> continue;
> }
> - joydev->corr[i].type = JS_CORR_BROKEN;
> - joydev->corr[i].prec = input_abs_get_fuzz(dev, j);
>
> - t = (input_abs_get_max(dev, j) + input_abs_get_min(dev, j)) / 2;
> - joydev->corr[i].coef[0] = t - input_abs_get_flat(dev, j);
> - joydev->corr[i].coef[1] = t + input_abs_get_flat(dev, j);
> + joydev_calculate_correction(dev, j, &joydev->corr[i]);
>
> - t = (input_abs_get_max(dev, j) - input_abs_get_min(dev, j)) / 2
> - - 2 * input_abs_get_flat(dev, j);
> - if (t) {
> - joydev->corr[i].coef[2] = (1 << 29) / t;
> - joydev->corr[i].coef[3] = (1 << 29) / t;
> + joydev->abs[i] =
> + joydev_correct(input_abs_get_val(dev, j),
> + joydev->corr + i);
>
> - joydev->abs[i] =
> - joydev_correct(input_abs_get_val(dev, j),
> - joydev->corr + i);
> - }
> }
>
> joydev->dev.devt = MKDEV(INPUT_MAJOR, minor);
> --
> 1.8.1.5
>
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