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diff --git a/Documentation/input/event-codes.rst b/Documentation/input/event-codes.rst new file mode 100644 index 000000000..b24b5343f --- /dev/null +++ b/Documentation/input/event-codes.rst @@ -0,0 +1,428 @@ +.. _input-event-codes: + +================= +Input event codes +================= + + +The input 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. + +A single hardware event generates multiple input events. Each input event +contains the new value of a single data item. A special event type, EV_SYN, is +used to separate input events into packets of input data changes occurring at +the same moment in time. In the following, the term "event" refers to a single +input event encompassing a type, code, and value. + +The input protocol is a stateful protocol. Events are emitted only when values +of event 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 +event code values using the EVIOCG* ioctls defined in linux/input.h. The event +reports supported by a device are also provided by sysfs in +class/input/event*/device/capabilities/, and the properties of a device are +provided in class/input/event*/device/properties. + +Event types +=========== + +Event 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 state changes of keyboards, buttons, or other key-like + devices. + +* EV_REL: + + - Used to describe relative axis value changes, e.g. moving the mouse 5 units + to the left. + +* EV_ABS: + + - Used to describe absolute axis value changes, e.g. describing the + coordinates of a touch on a touchscreen. + +* EV_MSC: + + - Used to describe miscellaneous input data 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. + +Event codes +=========== + +Event 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 packets of input data changes + occurring at the same moment in 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. + +* SYN_DROPPED: + + - Used to indicate buffer overrun in the evdev client's event queue. + Client should ignore all events up to and including next SYN_REPORT + event and query the device (using EVIOCG* ioctls) to obtain its + current state. + +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 all BTN_TOOL_<name> codes and the BTN_TOUCH code 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 BTN_TOOL_<name> + 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. + +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. The value is the number of detents moved on the wheel, the + physical size of which varies by device. For high-resolution wheels + this may be an approximation based on the high-resolution scroll events, + see REL_WHEEL_HI_RES. These event codes are legacy codes and + REL_WHEEL_HI_RES and REL_HWHEEL_HI_RES should be preferred where + available. + +* REL_WHEEL_HI_RES, REL_HWHEEL_HI_RES: + + - High-resolution scroll wheel data. The accumulated value 120 represents + movement by one detent. For devices that do not provide high-resolution + scrolling, the value is always a multiple of 120. For devices with + high-resolution scrolling, the value may be a fraction of 120. + + If a vertical scroll wheel supports high-resolution scrolling, this code + will be emitted in addition to REL_WHEEL or REL_HWHEEL. The REL_WHEEL + and REL_HWHEEL may be an approximation based on the high-resolution + scroll events. There is no guarantee that the high-resolution data + is a multiple of 120 at the time of an emulated REL_WHEEL or REL_HWHEEL + event. + +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 + event should only be emitted while the tool is hovering, meaning in close + proximity of the device and while the value of the BTN_TOUCH code is 0. If + the input device may be used freely in three dimensions, consider ABS_Z + instead. + - BTN_TOOL_<name> should be set to 1 when the tool comes into detectable + proximity and set to 0 when the tool leaves detectable proximity. + BTN_TOOL_<name> signals the type of tool that is currently detected by the + hardware and is otherwise independent of ABS_DISTANCE and/or BTN_TOUCH. + +* 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. + +Upon binding to a device or resuming from suspend, a driver must report +the current switch state. This ensures that the device, kernel, and userspace +state is in sync. + +Upon resume, if the switch state is the same as before suspend, then the input +subsystem will filter out the duplicate switch state reports. The driver does +not need to keep the state of the switch at any time. + +EV_MSC +------ + +EV_MSC events are used for input and output events that do not fall under other +categories. + +A few EV_MSC codes have special meaning: + +* MSC_TIMESTAMP: + + - Used to report the number of microseconds since the last reset. This event + should be coded as an uint32 value, which is allowed to wrap around with + no special consequence. It is assumed that the time difference between two + consecutive events is reliable on a reasonable time scale (hours). + A reset to zero can happen, in which case the time since the last event is + unknown. If the device does not provide this information, the driver must + not provide it to user space. + +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 event used specifically for power +management. Its usage is not well defined. To be addressed later. + +Device properties +================= + +Normally, userspace sets up an input device based on the data it emits, +i.e., the event types. In the case of two devices emitting the same event +types, additional information can be provided in the form of device +properties. + +INPUT_PROP_DIRECT + INPUT_PROP_POINTER +-------------------------------------- + +The INPUT_PROP_DIRECT property indicates that device coordinates should be +directly mapped to screen coordinates (not taking into account trivial +transformations, such as scaling, flipping and rotating). Non-direct input +devices require non-trivial transformation, such as absolute to relative +transformation for touchpads. Typical direct input devices: touchscreens, +drawing tablets; non-direct devices: touchpads, mice. + +The INPUT_PROP_POINTER property indicates that the device is not transposed +on the screen and thus requires use of an on-screen pointer to trace user's +movements. Typical pointer devices: touchpads, tablets, mice; non-pointer +device: touchscreen. + +If neither INPUT_PROP_DIRECT or INPUT_PROP_POINTER are set, the property is +considered undefined and the device type should be deduced in the +traditional way, using emitted event types. + +INPUT_PROP_BUTTONPAD +-------------------- + +For touchpads where the button is placed beneath the surface, such that +pressing down on the pad causes a button click, this property should be +set. Common in clickpad notebooks and macbooks from 2009 and onwards. + +Originally, the buttonpad property was coded into the bcm5974 driver +version field under the name integrated button. For backwards +compatibility, both methods need to be checked in userspace. + +INPUT_PROP_SEMI_MT +------------------ + +Some touchpads, most common between 2008 and 2011, can detect the presence +of multiple contacts without resolving the individual positions; only the +number of contacts and a rectangular shape is known. For such +touchpads, the semi-mt property should be set. + +Depending on the device, the rectangle may enclose all touches, like a +bounding box, or just some of them, for instance the two most recent +touches. The diversity makes the rectangle of limited use, but some +gestures can normally be extracted from it. + +If INPUT_PROP_SEMI_MT is not set, the device is assumed to be a true MT +device. + +INPUT_PROP_TOPBUTTONPAD +----------------------- + +Some laptops, most notably the Lenovo 40 series provide a trackstick +device but do not have physical buttons associated with the trackstick +device. Instead, the top area of the touchpad is marked to show +visual/haptic areas for left, middle, right buttons intended to be used +with the trackstick. + +If INPUT_PROP_TOPBUTTONPAD is set, userspace should emulate buttons +accordingly. This property does not affect kernel behavior. +The kernel does not provide button emulation for such devices but treats +them as any other INPUT_PROP_BUTTONPAD device. + +INPUT_PROP_ACCELEROMETER +------------------------ + +Directional axes on this device (absolute and/or relative x, y, z) represent +accelerometer data. Some devices also report gyroscope data, which devices +can report through the rotational axes (absolute and/or relative rx, ry, rz). + +All other axes retain their meaning. A device must not mix +regular directional axes and accelerometer axes on the same event node. + +Guidelines +========== + +The guidelines below ensure proper single-touch and multi-finger functionality. +For multi-touch functionality, see the multi-touch-protocol.txt document for +more information. + +Mice +---- + +REL_{X,Y} must be reported when the mouse moves. BTN_LEFT must be used to report +the primary button press. BTN_{MIDDLE,RIGHT,4,5,etc.} should be used to report +further buttons of the device. REL_WHEEL and REL_HWHEEL should be used to report +scroll wheel events where available. + +Touchscreens +------------ + +ABS_{X,Y} must be reported with the location of the touch. BTN_TOUCH must be +used to report when a touch is active on the screen. +BTN_{MOUSE,LEFT,MIDDLE,RIGHT} must not be reported as the result of touch +contact. BTN_TOOL_<name> events should be reported where possible. + +For new hardware, INPUT_PROP_DIRECT should be set. + +Trackpads +--------- + +Legacy trackpads that only provide relative position information must report +events like mice described above. + +Trackpads that provide absolute touch position must report ABS_{X,Y} for the +location of the touch. BTN_TOUCH should be used to report when a touch is active +on the trackpad. Where multi-finger support is available, BTN_TOOL_<name> should +be used to report the number of touches active on the trackpad. + +For new hardware, INPUT_PROP_POINTER should be set. + +Tablets +------- + +BTN_TOOL_<name> events must be reported when a stylus or other tool is active on +the tablet. ABS_{X,Y} must be reported with the location of the tool. BTN_TOUCH +should be used to report when the tool is in contact with the tablet. +BTN_{STYLUS,STYLUS2} should be used to report buttons on the tool itself. Any +button may be used for buttons on the tablet except BTN_{MOUSE,LEFT}. +BTN_{0,1,2,etc} are good generic codes for unlabeled buttons. Do not use +meaningful buttons, like BTN_FORWARD, unless the button is labeled for that +purpose on the device. + +For new hardware, both INPUT_PROP_DIRECT and INPUT_PROP_POINTER should be set. |