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Message-ID: <alpine.LNX.2.00.1306190129330.6750@pobox.suse.cz>
Date: Wed, 19 Jun 2013 01:30:43 +0200 (CEST)
From: Jiri Kosina <jkosina@...e.cz>
To: David Herrmann <dh.herrmann@...il.com>,
Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc: linux-input@...r.kernel.org,
Todd Showalter <todd@...ctronjump.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] input: document gamepad API and add extra
keycodes
On Sat, 15 Jun 2013, David Herrmann wrote:
> Until today all gamepad input drivers report their data differently. It is
> nearly impossible to write applications for more than one device in a
> generic way. Therefore, this patch introduces a uniform gamepad API which
> will be used for all new drivers.
>
> Instead of mapping buttons by their labels, we now map them by position.
> This allows applications to work with any gamepad regardless of the labels
> on the buttons. Furthermore, we standardize the ABS_* codes for analog
> triggers and sticks.
>
> For D-Pads the long overdue BTN_DPAD_* codes are introduced. They should
> be fairly obvious how to use. To avoid confusion, the action buttons now
> have BTN_EAST/SOUTH/WEST/NORTH aliases.
>
> Reported-by: Todd Showalter <todd@...ctronjump.com>
> Signed-off-by: David Herrmann <dh.herrmann@...il.com>
I definitely need to have Dmitry's Ack for this. If he's OK with 1/2, I am
fine with 2/2 patch for wiimote and will happily take it through my tree.
Thanks.
> ---
> Documentation/input/gamepad.txt | 156 ++++++++++++++++++++++++++++++++++++++++
> include/uapi/linux/input.h | 9 +++
> 2 files changed, 165 insertions(+)
> create mode 100644 Documentation/input/gamepad.txt
>
> diff --git a/Documentation/input/gamepad.txt b/Documentation/input/gamepad.txt
> new file mode 100644
> index 0000000..8002c89
> --- /dev/null
> +++ b/Documentation/input/gamepad.txt
> @@ -0,0 +1,156 @@
> + 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
> +
> +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).
> +
> +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).
> +
> +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@...il.com>
> diff --git a/include/uapi/linux/input.h b/include/uapi/linux/input.h
> index 935119c..7e15565 100644
> --- a/include/uapi/linux/input.h
> +++ b/include/uapi/linux/input.h
> @@ -507,10 +507,14 @@ struct input_keymap_entry {
>
> #define BTN_GAMEPAD 0x130
> #define BTN_A 0x130
> +#define BTN_SOUTH 0x130
> #define BTN_B 0x131
> +#define BTN_EAST 0x131
> #define BTN_C 0x132
> #define BTN_X 0x133
> +#define BTN_NORTH 0x133
> #define BTN_Y 0x134
> +#define BTN_WEST 0x134
> #define BTN_Z 0x135
> #define BTN_TL 0x136
> #define BTN_TR 0x137
> @@ -702,6 +706,11 @@ struct input_keymap_entry {
> #define KEY_CAMERA_LEFT 0x219
> #define KEY_CAMERA_RIGHT 0x21a
>
> +#define BTN_DPAD_UP 0x220
> +#define BTN_DPAD_DOWN 0x221
> +#define BTN_DPAD_LEFT 0x222
> +#define BTN_DPAD_RIGHT 0x223
> +
> #define BTN_TRIGGER_HAPPY 0x2c0
> #define BTN_TRIGGER_HAPPY1 0x2c0
> #define BTN_TRIGGER_HAPPY2 0x2c1
> --
> 1.8.3.1
>
--
Jiri Kosina
SUSE Labs
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