Input and games.

[Todd Showalter]

On Tue, Apr 23, 2013 at 7:25 AM, Pekka Paalanen <ppaalanen at gmail.com> wrote:

> what you describe here is very much a keymap-like database for game
> controllers: translating from button and axis indices to labels or
> symbols. However, having a brief chat with Daniel Stone, it seems we
> should not need these.
>
> Take a look at /usr/include/linux/input.h
>
> There you find definitions for BTN_A, BTN_X, BTN_START, ABS_X, ABS_Y,
> ABS_RX, ABS_RY, ABS_HATnn, and many more. The kernel evdev interface
> should alreay be giving out events with the correct label, so we would
> not need any mapping.
>
> Are you saying that the kernel gives out the labels wrong? If so, this
> should be fixed in the kernel drivers. One thing less to care about in
> Wayland. We "just" need to write the protocol for these devices, the
> labels should be already there.

    I'm not saying the labels are wrong; I assume they are correct.
The problem is that the labels are hardware-specific, at least for the
buttons.  That said, it looks like the axis values are being properly
labelled, which means we're way closer to sane behaviour than we were
last time I looked into this.

    I grabbed evtest and ran it with three devices; an xbox
controller, an xbox 360 controller, and a ps3 controller.  The
results:

xbox:
    - button
       A B X Y START THUMBL THUMBR
       Z (white button)
       C (black button)
       SELECT (back button)
    - axis
       ABS_X ABS_Y ABS_Z
       ABS_RX ABS_RY ABS_RZ
       ABS_HAT0X ABS_HAT0Y (dpad)

xbox 360:
    - button
       A B X Y START THUMBL THUMBR
       TL  TR
       MODE (home button)
       SELECT (back button)
    - axis
       ABS_X ABS_Y ABS_Z
       ABS_RX ABS_RY ABS_RZ
       ABS_HAT0X ABS_HAT0Y (dpad)

ps3:
  - button
    TRIGGER  THUMB  THUMB2
    TOP TOP2 PINKIE BASE  BASE2
    BASE3  BASE3  BASE4  BASE5
    BASE6  DEAD  TRIGGER_HAPPY17
    TRIGGER_HAPPY18  TRIGGER_HAPPY19
  - axis
    ABS_X  ABS_Y  ABS_Z  ABS_RZ  ABS_MISC

    The xbox controller and the xbox 360 controller are more or less
the same; the 360 controller has a couple of shoulder buttons instead
of a the black and white buttons, and (somewhat oddly) the "back"
buttons come in as "select", but that's workable.

    It all rather goes pear-shaped when we get beyond that, though.
The PS3 controller, while physically quite similar to the other two,
even down to the placement of controls and how the controls are
clustered, comes in completely differently.  There is not a single
button in common between the PS3 controller and the XBox controllers
as reported by evdev, despite the PS3 controller having buttons
physically labelled "start" and "select", plus direct equivalents to
many of the XBox 360 controller's parts (ie: TL, TR, MODE, ABS_HAT0X,
ABS_HAT0Y, ABS_RX, ABS_RY...).

    The PS3 controller also has several "(?)" entries for buttons and
axis values, and also appears to have (if I understand correctly) a
bunch of codes for a multitouch panel?  I couldn't tell you what the
right or left stick axis values are in the above, because though I did
build my kernel with ps3 controller support, and evtest did see it and
dump the supported event list, I get no events logged from... ah, ok,
I have to hit the PS button to get it to actually work.  And now
there's a torrent of what I assume is accelerometer data coming in on
"(?)" events.

    It turns out the left stick is ABS_X and ABS_Y, and right stick is
ABS_Z and ABS_RZ.  I suspect this is just broken somehow.  Maybe the
ps3 gamepad kernel driver is still a work in progress?  But this is
the kind of thing I was talking about; the data I get from a ps3
gamepad is mapped totally differently from the data I get from an xbox
gamepad, so from a game point of view, even if all I want is a
joystick, a jump button and a shoot button, I still have to care what
particular kind of gamepad the player has plugged in because I'm going
to get completely different button messages depending on what kind of
pad is plugged in.

> The current behaviour can be checked with evtest:
> http://cgit.freedesktop.org/evtest/
> Was that what you used to check the controller events?

   Previously, I'd been dumping data from the libjsw interface, and
then dumping data by going directly through evdev.  This time I used
evtest.

                                       Todd.

--
 Todd Showalter, President,
 Electron Jump Games, Inc.