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diff --git a/Documentation/input/gamepad.txt b/Documentation/input/gamepad.txt new file mode 100644 index 000000000000..31bb6a4029ef --- /dev/null +++ b/Documentation/input/gamepad.txt @@ -0,0 +1,159 @@ + Linux Gamepad API +---------------------------------------------------------------------------- + +1. Intro +~~~~~~~~ +Linux provides many different input drivers for gamepad hardware. To avoid +having user-space deal with different button-mappings for each gamepad, this +document defines how gamepads are supposed to report their data. + +2. Geometry +~~~~~~~~~~~ +As "gamepad" we define devices which roughly look like this: + + ____________________________ __ + / [__ZL__] [__ZR__] \ | + / [__ TL __] [__ TR __] \ | Front Triggers + __/________________________________\__ __| + / _ \ | + / /\ __ (N) \ | + / || __ |MO| __ _ _ \ | Main Pad + | <===DP===> |SE| |ST| (W) -|- (E) | | + \ || ___ ___ _ / | + /\ \/ / \ / \ (S) /\ __| + / \________ | LS | ____ | RS | ________/ \ | + | / \ \___/ / \ \___/ / \ | | Control Sticks + | / \_____/ \_____/ \ | __| + | / \ | + \_____/ \_____/ + + |________|______| |______|___________| + D-Pad Left Right Action Pad + Stick Stick + + |_____________| + Menu Pad + +Most gamepads have the following features: + - Action-Pad + 4 buttons in diamonds-shape (on the right side). The buttons are + differently labeled on most devices so we define them as NORTH, + SOUTH, WEST and EAST. + - D-Pad (Direction-pad) + 4 buttons (on the left side) that point up, down, left and right. + - Menu-Pad + Different constellations, but most-times 2 buttons: SELECT - START + Furthermore, many gamepads have a fancy branded button that is used as + special system-button. It often looks different to the other buttons and + is used to pop up system-menus or system-settings. + - Analog-Sticks + Analog-sticks provide freely moveable sticks to control directions. Not + all devices have both or any, but they are present at most times. + Analog-sticks may also provide a digital button if you press them. + - Triggers + Triggers are located on the upper-side of the pad in vertical direction. + Not all devices provide them, but the upper buttons are normally named + Left- and Right-Triggers, the lower buttons Z-Left and Z-Right. + - Rumble + Many devices provide force-feedback features. But are mostly just + simple rumble motors. + +3. Detection +~~~~~~~~~~~~ +All gamepads that follow the protocol described here map BTN_GAMEPAD. This is +an alias for BTN_SOUTH/BTN_A. It can be used to identify a gamepad as such. +However, not all gamepads provide all features, so you need to test for all +features that you need, first. How each feature is mapped is described below. + +Legacy drivers often don't comply to these rules. As we cannot change them +for backwards-compatibility reasons, you need to provide fixup mappings in +user-space yourself. Some of them might also provide module-options that +change the mappings so you can adivce users to set these. + +All new gamepads are supposed to comply with this mapping. Please report any +bugs, if they don't. + +There are a lot of less-featured/less-powerful devices out there, which re-use +the buttons from this protocol. However, they try to do this in a compatible +fashion. For example, the "Nintendo Wii Nunchuk" provides two trigger buttons +and one analog stick. It reports them as if it were a gamepad with only one +analog stick and two trigger buttons on the right side. +But that means, that if you only support "real" gamepads, you must test +devices for _all_ reported events that you need. Otherwise, you will also get +devices that report a small subset of the events. + +No other devices, that do not look/feel like a gamepad, shall report these +events. + +4. Events +~~~~~~~~~ +Gamepads report the following events: + +Action-Pad: + Every gamepad device has at least 2 action buttons. This means, that every + device reports BTN_SOUTH (which BTN_GAMEPAD is an alias for). Regardless + of the labels on the buttons, the codes are sent according to the + physical position of the buttons. + Please note that 2- and 3-button pads are fairly rare and old. You might + want to filter gamepads that do not report all four. + 2-Button Pad: + If only 2 action-buttons are present, they are reported as BTN_SOUTH and + BTN_EAST. For vertical layouts, the upper button is BTN_EAST. For + horizontal layouts, the button more on the right is BTN_EAST. + 3-Button Pad: + If only 3 action-buttons are present, they are reported as (from left + to right): BTN_WEST, BTN_SOUTH, BTN_EAST + If the buttons are aligned perfectly vertically, they are reported as + (from top down): BTN_WEST, BTN_SOUTH, BTN_EAST + 4-Button Pad: + If all 4 action-buttons are present, they can be aligned in two + different formations. If diamond-shaped, they are reported as BTN_NORTH, + BTN_WEST, BTN_SOUTH, BTN_EAST according to their physical location. + If rectangular-shaped, the upper-left button is BTN_NORTH, lower-left + is BTN_WEST, lower-right is BTN_SOUTH and upper-right is BTN_EAST. + +D-Pad: + Every gamepad provides a D-Pad with four directions: Up, Down, Left, Right + Some of these are available as digital buttons, some as analog buttons. Some + may even report both. The kernel does not convert between these so + applications should support both and choose what is more appropriate if + both are reported. + Digital buttons are reported as: + BTN_DPAD_* + Analog buttons are reported as: + ABS_HAT0X and ABS_HAT0Y + (for ABS values negative is left/up, positive is right/down) + +Analog-Sticks: + The left analog-stick is reported as ABS_X, ABS_Y. The right analog stick is + reported as ABS_RX, ABS_RY. Zero, one or two sticks may be present. + If analog-sticks provide digital buttons, they are mapped accordingly as + BTN_THUMBL (first/left) and BTN_THUMBR (second/right). + (for ABS values negative is left/up, positive is right/down) + +Triggers: + Trigger buttons can be available as digital or analog buttons or both. User- + space must correctly deal with any situation and choose the most appropriate + mode. + Upper trigger buttons are reported as BTN_TR or ABS_HAT1X (right) and BTN_TL + or ABS_HAT1Y (left). Lower trigger buttons are reported as BTN_TR2 or + ABS_HAT2X (right/ZR) and BTN_TL2 or ABS_HAT2Y (left/ZL). + If only one trigger-button combination is present (upper+lower), they are + reported as "right" triggers (BTN_TR/ABS_HAT1X). + (ABS trigger values start at 0, pressure is reported as positive values) + +Menu-Pad: + Menu buttons are always digital and are mapped according to their location + instead of their labels. That is: + 1-button Pad: Mapped as BTN_START + 2-button Pad: Left button mapped as BTN_SELECT, right button mapped as + BTN_START + Many pads also have a third button which is branded or has a special symbol + and meaning. Such buttons are mapped as BTN_MODE. Examples are the Nintendo + "HOME" button, the XBox "X"-button or Sony "P" button. + +Rumble: + Rumble is adverticed as FF_RUMBLE. + +---------------------------------------------------------------------------- + Written 2013 by David Herrmann <dh.herrmann@gmail.com> |
