This commit adds the file Documentation/input/evdev-codes.txt. Cc: Henrik Rydberg <rydberg@xxxxxxxxxxx> Cc: Chris Bagwell <chris@xxxxxxxxxxxxxx> Cc: Peter Hutterer <peter.hutterer@xxxxxxxxx> Cc: Nikolai Kondrashov <spbnick@xxxxxxxxx> Cc: linux-input@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Signed-off-by: Chase Douglas <chase.douglas@xxxxxxxxxxxxx> --- Documentation/input/evdev-codes.txt | 206 +++++++++++++++++++++++++++++++++++ 1 files changed, 206 insertions(+), 0 deletions(-) create mode 100644 Documentation/input/evdev-codes.txt diff --git a/Documentation/input/evdev-codes.txt b/Documentation/input/evdev-codes.txt new file mode 100644 index 0000000..8d7262c --- /dev/null +++ b/Documentation/input/evdev-codes.txt @@ -0,0 +1,206 @@ +The evdev protocol uses a map of types and codes to express input device values +to userspace. This document describes the types and codes and how and when they +may be used. + +The evdev protocol is a stateful protocol. Events are emitted only when values +of evdev codes have changed. However, the state is maintained within the Linux +input subsystem; drivers do not need to maintain the state and may attempt to +emit unchanged values without harm. Userspace may obtain the current state of +evdev code values using the EVIOCGABS ioctl defined in linux/input.h. + +Types: +========== +Types are groupings of codes under a logical input construct. Each type has a +set of applicable codes to be used in generating events. See the Codes section +for details on valid codes for each type. + +* EV_SYN: + - Used as markers to separate events. Events may be separated in time or in + space, such as with the multitouch protocol. + +* EV_KEY: + - Used to describe keyboard and other key-like input events. + +* EV_REL: + - Used to describe relative input events, e.g. moving the mouse 5 units to the + left. + +* EV_ABS: + - Used to describe absolute input events, e.g. describing the coordinates of a + touch on a touchscreen. + +* EV_MSC: + - Used to describe miscellaneous input events that do not fit into other + types. + +* EV_SW: + - Used to describe binary state input switches. + +* EV_LED: + - Used to turn LEDs on devices on and off. + +* EV_SND: + - Used to output sound to devices. + +* EV_REP: + - Used for autorepeating devices. + +* EV_FF: + - Used to send force feedback commands to an input device. + +* EV_PWR: + - A special type for power button and switch input. + +* EV_FF_STATUS: + - Used to receive force feedback device status. + +Codes: +========== +Codes define the precise type of event. + +EV_SYN: +---------- +EV_SYN event values are undefined. Their usage is +defined only by when they are sent in the evdev event stream. + +* SYN_REPORT: + - Used to synchronize and separate events into frames of time. For example, + motion of a mouse may set the REL_X and REL_Y values for one motion, then + emit a SYN_REPORT. The next motion will emit more REL_X and REL_Y values and + send another SYN_REPORT. + +* SYN_CONFIG: + - TBD + +* SYN_MT_REPORT: + - Used to synchronize and separate touch events. See the + multi-touch-protocol.txt document for more information. + +EV_KEY: +---------- +EV_KEY events take the form KEY_<name> or BTN_<name>. For example, KEY_A is used +to represent the 'A' key on a keyboard. When a key is depressed, an event with +the key's code is emitted with value 1. When the key is released, an event is +emitted with value 0. Some hardware send events when a key is repeated. These +events have a value of 2. In general, KEY_<name> is used for keyboard keys, and +BTN_<name> is used for other types of momentary switch events. + +A few EV_KEY codes have special meanings: + +* BTN_TOOL_<name>: + - These codes are used in conjunction with input trackpads, tablets, and + touchscreens. These devices may be used with fingers, pens, or other tools. + When an event occurs and a tool is used, the corresponding BTN_TOOL_<name> + code should be set to a value of 1. When the tool is no longer interacting + with the input device, the BTN_TOOL_<name> code should be reset to 0. All + trackpads, tablets, and touchscreens should use at least one BTN_TOOL_<name> + code when events are generated. + +* BTN_TOUCH: + BTN_TOUCH is used for touch contact. While an input tool is determined to be + within meaningful physical contact, the value of this property must be set + to 1. Meaningful physical contact may mean any contact, or it may mean + contact conditioned by an implementation defined property. For example, a + touchpad may set the value to 1 only when the touch pressure rises above a + certain value. BTN_TOUCH may be combined with BTN_TOOL_<name> codes. For + example, a pen tablet may set BTN_TOOL_PEN to 1 and BTN_TOUCH to 0 while the + pen is hovering over but not touching the tablet surface. + +Note: For appropriate function of the legacy mousedev emulation driver, +BTN_TOUCH must be the first evdev code emitted in a synchronization frame. + +Note: Historically a touch device with BTN_TOOL_FINGER and BTN_TOUCH was +interpreted as a touchpad by userspace, while a similar device without +BTN_TOOL_FINGER was interpreted as a touchscreen. For backwards compatibility +with current userspace it is recommended to follow this distinction. In the +future, this distinction will be deprecated and the device properties ioctl +EVIOCGPROP, defined in linux/input.h, will be used to convey the device type. + +* BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP, BTN_TOOL_TRIPLETAP, BTN_TOOL_QUADTAP: + - These codes denote one, two, three, and four finger interaction on a + trackpad or touchscreen. For example, if the user uses two fingers and moves + them on the touchpad in an effort to scroll content on screen, + BTN_TOOL_DOUBLETAP should be set to value 1 for the duration of the motion. + Note that these codes and the BTN_TOOL_<name> and BTN_TOUCH codes are + orthogonal in purpose. A trackpad event generated by finger touches should + generate events for one code from each group. At most only one of these + codes should have a value of 1 during any synchronization frame. + +Note: Historically some drivers emitted multiple of the finger count codes with +a value of 1 in the same synchronization frame. This usage is deprecated. + +Note: In multitouch drivers, the input_mt_report_finger_count() function should +be used to emit these codes. Please see multi-touch-protocol.txt for details. + +* KEY_SUSPEND, KEY_POWER: + - These codes are reserved for the EV_PWR type. + +EV_REL: +---------- +EV_REL events describe relative changes in a property. For example, a mouse may +move to the left by a certain number of units, but its absolute position in +space is unknown. If the absolute position is known, EV_ABS codes should be used +instead of EV_REL codes. + +A few EV_REL codes have special meanings: + +* REL_WHEEL, REL_HWHEEL: + - These codes are used for vertical and horizontal scroll wheels, + respectively. + +EV_ABS: +---------- +EV_ABS events describe absolute changes in a property. For example, a touchpad +may emit coordinates for a touch location. + +A few EV_ABS codes have special meanings: + +* ABS_DISTANCE: + - Used to describe the distance of a tool from an interaction surface. This + should only be used while the tool is hovering, meaning in close proximity + of the device. If the input device may be used freely in three dimensions, + consider ABS_Z instead. + +* ABS_MT_<name>: + - Used to describe multitouch input events. Please see + multi-touch-protocol.txt for details. + +EV_SW: +---------- +EV_SW events describe stateful binary switches. For example, the SW_LID code is +used to denote when a laptop lid is closed. + +EV_MSC: +---------- +EV_MSC events are used for input and output events that do not fall under other +categories. + +EV_LED: +---------- +EV_LED events are used for input and output to set and query the state of +various LEDs on devices. + +EV_REP: +---------- +EV_REP events are used for specifying autorepeating events. + +EV_SND: +---------- +EV_SND events are used for sending sound commands to simple sound output +devices. + +EV_FF: +---------- +EV_FF events are used to initialize a force feedback capable device and to cause +such device to feedback. + +EV_PWR: +---------- +EV_PWR events are a special type of key event used specifically for monitoring +power buttons and switches. The two codes in use are: + +* KEY_POWER: + - Used to denote a power button event. + +* KEY_SUSPEND: + - Used to denote a suspend button event. -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
