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1 | .. _input-event-codes: |
2 | ||
acbdca8b MCC |
3 | ================= |
4 | Input event codes | |
5 | ================= | |
6 | ||
7 | ||
b1e064b8 CD |
8 | The input protocol uses a map of types and codes to express input device values |
9 | to userspace. This document describes the types and codes and how and when they | |
10 | may be used. | |
11 | ||
12 | A single hardware event generates multiple input events. Each input event | |
13 | contains the new value of a single data item. A special event type, EV_SYN, is | |
14 | used to separate input events into packets of input data changes occurring at | |
15 | the same moment in time. In the following, the term "event" refers to a single | |
16 | input event encompassing a type, code, and value. | |
17 | ||
18 | The input protocol is a stateful protocol. Events are emitted only when values | |
19 | of event codes have changed. However, the state is maintained within the Linux | |
20 | input subsystem; drivers do not need to maintain the state and may attempt to | |
21 | emit unchanged values without harm. Userspace may obtain the current state of | |
22 | event code values using the EVIOCG* ioctls defined in linux/input.h. The event | |
23 | reports supported by a device are also provided by sysfs in | |
24 | class/input/event*/device/capabilities/, and the properties of a device are | |
25 | provided in class/input/event*/device/properties. | |
26 | ||
acbdca8b | 27 | Event types |
d04df023 | 28 | =========== |
acbdca8b | 29 | |
d04df023 HR |
30 | Event types are groupings of codes under a logical input construct. Each |
31 | type has a set of applicable codes to be used in generating events. See the | |
32 | Codes section for details on valid codes for each type. | |
b1e064b8 CD |
33 | |
34 | * EV_SYN: | |
acbdca8b | 35 | |
b1e064b8 CD |
36 | - Used as markers to separate events. Events may be separated in time or in |
37 | space, such as with the multitouch protocol. | |
38 | ||
39 | * EV_KEY: | |
acbdca8b | 40 | |
b1e064b8 CD |
41 | - Used to describe state changes of keyboards, buttons, or other key-like |
42 | devices. | |
43 | ||
44 | * EV_REL: | |
acbdca8b | 45 | |
b1e064b8 CD |
46 | - Used to describe relative axis value changes, e.g. moving the mouse 5 units |
47 | to the left. | |
48 | ||
49 | * EV_ABS: | |
acbdca8b | 50 | |
b1e064b8 CD |
51 | - Used to describe absolute axis value changes, e.g. describing the |
52 | coordinates of a touch on a touchscreen. | |
53 | ||
54 | * EV_MSC: | |
acbdca8b | 55 | |
b1e064b8 CD |
56 | - Used to describe miscellaneous input data that do not fit into other types. |
57 | ||
58 | * EV_SW: | |
acbdca8b | 59 | |
b1e064b8 CD |
60 | - Used to describe binary state input switches. |
61 | ||
62 | * EV_LED: | |
acbdca8b | 63 | |
b1e064b8 CD |
64 | - Used to turn LEDs on devices on and off. |
65 | ||
66 | * EV_SND: | |
acbdca8b | 67 | |
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68 | - Used to output sound to devices. |
69 | ||
70 | * EV_REP: | |
acbdca8b | 71 | |
b1e064b8 CD |
72 | - Used for autorepeating devices. |
73 | ||
74 | * EV_FF: | |
acbdca8b | 75 | |
b1e064b8 CD |
76 | - Used to send force feedback commands to an input device. |
77 | ||
78 | * EV_PWR: | |
acbdca8b | 79 | |
b1e064b8 CD |
80 | - A special type for power button and switch input. |
81 | ||
82 | * EV_FF_STATUS: | |
acbdca8b | 83 | |
b1e064b8 CD |
84 | - Used to receive force feedback device status. |
85 | ||
acbdca8b | 86 | Event codes |
d04df023 | 87 | =========== |
acbdca8b | 88 | |
d04df023 | 89 | Event codes define the precise type of event. |
b1e064b8 | 90 | |
acbdca8b MCC |
91 | EV_SYN |
92 | ------ | |
93 | ||
b1e064b8 CD |
94 | EV_SYN event values are undefined. Their usage is defined only by when they are |
95 | sent in the evdev event stream. | |
96 | ||
97 | * SYN_REPORT: | |
acbdca8b | 98 | |
b1e064b8 CD |
99 | - Used to synchronize and separate events into packets of input data changes |
100 | occurring at the same moment in time. For example, motion of a mouse may set | |
101 | the REL_X and REL_Y values for one motion, then emit a SYN_REPORT. The next | |
102 | motion will emit more REL_X and REL_Y values and send another SYN_REPORT. | |
103 | ||
104 | * SYN_CONFIG: | |
acbdca8b | 105 | |
b1e064b8 CD |
106 | - TBD |
107 | ||
108 | * SYN_MT_REPORT: | |
acbdca8b | 109 | |
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110 | - Used to synchronize and separate touch events. See the |
111 | multi-touch-protocol.txt document for more information. | |
112 | ||
9fb0f14e | 113 | * SYN_DROPPED: |
acbdca8b | 114 | |
9fb0f14e JB |
115 | - Used to indicate buffer overrun in the evdev client's event queue. |
116 | Client should ignore all events up to and including next SYN_REPORT | |
117 | event and query the device (using EVIOCG* ioctls) to obtain its | |
118 | current state. | |
119 | ||
acbdca8b MCC |
120 | EV_KEY |
121 | ------ | |
122 | ||
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123 | EV_KEY events take the form KEY_<name> or BTN_<name>. For example, KEY_A is used |
124 | to represent the 'A' key on a keyboard. When a key is depressed, an event with | |
125 | the key's code is emitted with value 1. When the key is released, an event is | |
126 | emitted with value 0. Some hardware send events when a key is repeated. These | |
127 | events have a value of 2. In general, KEY_<name> is used for keyboard keys, and | |
128 | BTN_<name> is used for other types of momentary switch events. | |
129 | ||
130 | A few EV_KEY codes have special meanings: | |
131 | ||
132 | * BTN_TOOL_<name>: | |
acbdca8b | 133 | |
b1e064b8 CD |
134 | - These codes are used in conjunction with input trackpads, tablets, and |
135 | touchscreens. These devices may be used with fingers, pens, or other tools. | |
136 | When an event occurs and a tool is used, the corresponding BTN_TOOL_<name> | |
137 | code should be set to a value of 1. When the tool is no longer interacting | |
138 | with the input device, the BTN_TOOL_<name> code should be reset to 0. All | |
139 | trackpads, tablets, and touchscreens should use at least one BTN_TOOL_<name> | |
140 | code when events are generated. | |
141 | ||
142 | * BTN_TOUCH: | |
acbdca8b | 143 | |
b1e064b8 CD |
144 | BTN_TOUCH is used for touch contact. While an input tool is determined to be |
145 | within meaningful physical contact, the value of this property must be set | |
146 | to 1. Meaningful physical contact may mean any contact, or it may mean | |
147 | contact conditioned by an implementation defined property. For example, a | |
148 | touchpad may set the value to 1 only when the touch pressure rises above a | |
149 | certain value. BTN_TOUCH may be combined with BTN_TOOL_<name> codes. For | |
150 | example, a pen tablet may set BTN_TOOL_PEN to 1 and BTN_TOUCH to 0 while the | |
151 | pen is hovering over but not touching the tablet surface. | |
152 | ||
153 | Note: For appropriate function of the legacy mousedev emulation driver, | |
154 | BTN_TOUCH must be the first evdev code emitted in a synchronization frame. | |
155 | ||
156 | Note: Historically a touch device with BTN_TOOL_FINGER and BTN_TOUCH was | |
157 | interpreted as a touchpad by userspace, while a similar device without | |
158 | BTN_TOOL_FINGER was interpreted as a touchscreen. For backwards compatibility | |
159 | with current userspace it is recommended to follow this distinction. In the | |
160 | future, this distinction will be deprecated and the device properties ioctl | |
161 | EVIOCGPROP, defined in linux/input.h, will be used to convey the device type. | |
162 | ||
163 | * BTN_TOOL_FINGER, BTN_TOOL_DOUBLETAP, BTN_TOOL_TRIPLETAP, BTN_TOOL_QUADTAP: | |
acbdca8b | 164 | |
b1e064b8 CD |
165 | - These codes denote one, two, three, and four finger interaction on a |
166 | trackpad or touchscreen. For example, if the user uses two fingers and moves | |
167 | them on the touchpad in an effort to scroll content on screen, | |
168 | BTN_TOOL_DOUBLETAP should be set to value 1 for the duration of the motion. | |
169 | Note that all BTN_TOOL_<name> codes and the BTN_TOUCH code are orthogonal in | |
170 | purpose. A trackpad event generated by finger touches should generate events | |
171 | for one code from each group. At most only one of these BTN_TOOL_<name> | |
172 | codes should have a value of 1 during any synchronization frame. | |
173 | ||
174 | Note: Historically some drivers emitted multiple of the finger count codes with | |
175 | a value of 1 in the same synchronization frame. This usage is deprecated. | |
176 | ||
177 | Note: In multitouch drivers, the input_mt_report_finger_count() function should | |
178 | be used to emit these codes. Please see multi-touch-protocol.txt for details. | |
179 | ||
acbdca8b MCC |
180 | EV_REL |
181 | ------ | |
182 | ||
b1e064b8 CD |
183 | EV_REL events describe relative changes in a property. For example, a mouse may |
184 | move to the left by a certain number of units, but its absolute position in | |
185 | space is unknown. If the absolute position is known, EV_ABS codes should be used | |
186 | instead of EV_REL codes. | |
187 | ||
188 | A few EV_REL codes have special meanings: | |
189 | ||
190 | * REL_WHEEL, REL_HWHEEL: | |
acbdca8b | 191 | |
b1e064b8 | 192 | - These codes are used for vertical and horizontal scroll wheels, |
ffe0e7cf | 193 | respectively. |
b1e064b8 | 194 | |
acbdca8b MCC |
195 | EV_ABS |
196 | ------ | |
197 | ||
b1e064b8 CD |
198 | EV_ABS events describe absolute changes in a property. For example, a touchpad |
199 | may emit coordinates for a touch location. | |
200 | ||
201 | A few EV_ABS codes have special meanings: | |
202 | ||
203 | * ABS_DISTANCE: | |
acbdca8b | 204 | |
b1e064b8 CD |
205 | - Used to describe the distance of a tool from an interaction surface. This |
206 | event should only be emitted while the tool is hovering, meaning in close | |
207 | proximity of the device and while the value of the BTN_TOUCH code is 0. If | |
208 | the input device may be used freely in three dimensions, consider ABS_Z | |
209 | instead. | |
7eb5ca09 PH |
210 | - BTN_TOOL_<name> should be set to 1 when the tool comes into detectable |
211 | proximity and set to 0 when the tool leaves detectable proximity. | |
212 | BTN_TOOL_<name> signals the type of tool that is currently detected by the | |
213 | hardware and is otherwise independent of ABS_DISTANCE and/or BTN_TOUCH. | |
b1e064b8 CD |
214 | |
215 | * ABS_MT_<name>: | |
acbdca8b | 216 | |
b1e064b8 CD |
217 | - Used to describe multitouch input events. Please see |
218 | multi-touch-protocol.txt for details. | |
219 | ||
acbdca8b MCC |
220 | EV_SW |
221 | ----- | |
222 | ||
b1e064b8 CD |
223 | EV_SW events describe stateful binary switches. For example, the SW_LID code is |
224 | used to denote when a laptop lid is closed. | |
225 | ||
226 | Upon binding to a device or resuming from suspend, a driver must report | |
227 | the current switch state. This ensures that the device, kernel, and userspace | |
228 | state is in sync. | |
229 | ||
230 | Upon resume, if the switch state is the same as before suspend, then the input | |
231 | subsystem will filter out the duplicate switch state reports. The driver does | |
232 | not need to keep the state of the switch at any time. | |
233 | ||
acbdca8b MCC |
234 | EV_MSC |
235 | ------ | |
236 | ||
b1e064b8 CD |
237 | EV_MSC events are used for input and output events that do not fall under other |
238 | categories. | |
239 | ||
af8036dd BT |
240 | A few EV_MSC codes have special meaning: |
241 | ||
242 | * MSC_TIMESTAMP: | |
acbdca8b | 243 | |
af8036dd BT |
244 | - Used to report the number of microseconds since the last reset. This event |
245 | should be coded as an uint32 value, which is allowed to wrap around with | |
246 | no special consequence. It is assumed that the time difference between two | |
247 | consecutive events is reliable on a reasonable time scale (hours). | |
248 | A reset to zero can happen, in which case the time since the last event is | |
249 | unknown. If the device does not provide this information, the driver must | |
250 | not provide it to user space. | |
251 | ||
acbdca8b MCC |
252 | EV_LED |
253 | ------ | |
254 | ||
b1e064b8 CD |
255 | EV_LED events are used for input and output to set and query the state of |
256 | various LEDs on devices. | |
257 | ||
acbdca8b MCC |
258 | EV_REP |
259 | ------ | |
260 | ||
b1e064b8 CD |
261 | EV_REP events are used for specifying autorepeating events. |
262 | ||
acbdca8b MCC |
263 | EV_SND |
264 | ------ | |
265 | ||
b1e064b8 CD |
266 | EV_SND events are used for sending sound commands to simple sound output |
267 | devices. | |
268 | ||
acbdca8b MCC |
269 | EV_FF |
270 | ----- | |
271 | ||
b1e064b8 CD |
272 | EV_FF events are used to initialize a force feedback capable device and to cause |
273 | such device to feedback. | |
274 | ||
acbdca8b MCC |
275 | EV_PWR |
276 | ------ | |
277 | ||
b1e064b8 | 278 | EV_PWR events are a special type of event used specifically for power |
ad4a6ebe | 279 | management. Its usage is not well defined. To be addressed later. |
b1e064b8 | 280 | |
acbdca8b | 281 | Device properties |
d04df023 | 282 | ================= |
acbdca8b | 283 | |
d04df023 HR |
284 | Normally, userspace sets up an input device based on the data it emits, |
285 | i.e., the event types. In the case of two devices emitting the same event | |
286 | types, additional information can be provided in the form of device | |
287 | properties. | |
288 | ||
acbdca8b | 289 | INPUT_PROP_DIRECT + INPUT_PROP_POINTER |
d04df023 | 290 | -------------------------------------- |
acbdca8b | 291 | |
d04df023 HR |
292 | The INPUT_PROP_DIRECT property indicates that device coordinates should be |
293 | directly mapped to screen coordinates (not taking into account trivial | |
294 | transformations, such as scaling, flipping and rotating). Non-direct input | |
295 | devices require non-trivial transformation, such as absolute to relative | |
296 | transformation for touchpads. Typical direct input devices: touchscreens, | |
297 | drawing tablets; non-direct devices: touchpads, mice. | |
298 | ||
299 | The INPUT_PROP_POINTER property indicates that the device is not transposed | |
300 | on the screen and thus requires use of an on-screen pointer to trace user's | |
301 | movements. Typical pointer devices: touchpads, tablets, mice; non-pointer | |
302 | device: touchscreen. | |
303 | ||
304 | If neither INPUT_PROP_DIRECT or INPUT_PROP_POINTER are set, the property is | |
305 | considered undefined and the device type should be deduced in the | |
306 | traditional way, using emitted event types. | |
307 | ||
acbdca8b | 308 | INPUT_PROP_BUTTONPAD |
d04df023 | 309 | -------------------- |
acbdca8b | 310 | |
d04df023 HR |
311 | For touchpads where the button is placed beneath the surface, such that |
312 | pressing down on the pad causes a button click, this property should be | |
313 | set. Common in clickpad notebooks and macbooks from 2009 and onwards. | |
314 | ||
315 | Originally, the buttonpad property was coded into the bcm5974 driver | |
316 | version field under the name integrated button. For backwards | |
317 | compatibility, both methods need to be checked in userspace. | |
318 | ||
acbdca8b | 319 | INPUT_PROP_SEMI_MT |
d04df023 | 320 | ------------------ |
acbdca8b | 321 | |
d04df023 HR |
322 | Some touchpads, most common between 2008 and 2011, can detect the presence |
323 | of multiple contacts without resolving the individual positions; only the | |
324 | number of contacts and a rectangular shape is known. For such | |
325 | touchpads, the semi-mt property should be set. | |
326 | ||
327 | Depending on the device, the rectangle may enclose all touches, like a | |
328 | bounding box, or just some of them, for instance the two most recent | |
329 | touches. The diversity makes the rectangle of limited use, but some | |
330 | gestures can normally be extracted from it. | |
331 | ||
332 | If INPUT_PROP_SEMI_MT is not set, the device is assumed to be a true MT | |
333 | device. | |
334 | ||
acbdca8b | 335 | INPUT_PROP_TOPBUTTONPAD |
f62d14a8 | 336 | ----------------------- |
acbdca8b MCC |
337 | |
338 | Some laptops, most notably the Lenovo 40 series provide a trackstick | |
f62d14a8 PH |
339 | device but do not have physical buttons associated with the trackstick |
340 | device. Instead, the top area of the touchpad is marked to show | |
341 | visual/haptic areas for left, middle, right buttons intended to be used | |
342 | with the trackstick. | |
343 | ||
344 | If INPUT_PROP_TOPBUTTONPAD is set, userspace should emulate buttons | |
345 | accordingly. This property does not affect kernel behavior. | |
346 | The kernel does not provide button emulation for such devices but treats | |
347 | them as any other INPUT_PROP_BUTTONPAD device. | |
348 | ||
33096777 | 349 | INPUT_PROP_ACCELEROMETER |
acbdca8b MCC |
350 | ------------------------ |
351 | ||
33096777 | 352 | Directional axes on this device (absolute and/or relative x, y, z) represent |
227c011b RC |
353 | accelerometer data. Some devices also report gyroscope data, which devices |
354 | can report through the rotational axes (absolute and/or relative rx, ry, rz). | |
355 | ||
356 | All other axes retain their meaning. A device must not mix | |
33096777 PH |
357 | regular directional axes and accelerometer axes on the same event node. |
358 | ||
acbdca8b | 359 | Guidelines |
b1e064b8 | 360 | ========== |
acbdca8b | 361 | |
b1e064b8 CD |
362 | The guidelines below ensure proper single-touch and multi-finger functionality. |
363 | For multi-touch functionality, see the multi-touch-protocol.txt document for | |
364 | more information. | |
365 | ||
acbdca8b MCC |
366 | Mice |
367 | ---- | |
368 | ||
b1e064b8 CD |
369 | REL_{X,Y} must be reported when the mouse moves. BTN_LEFT must be used to report |
370 | the primary button press. BTN_{MIDDLE,RIGHT,4,5,etc.} should be used to report | |
371 | further buttons of the device. REL_WHEEL and REL_HWHEEL should be used to report | |
372 | scroll wheel events where available. | |
373 | ||
acbdca8b MCC |
374 | Touchscreens |
375 | ------------ | |
376 | ||
b1e064b8 CD |
377 | ABS_{X,Y} must be reported with the location of the touch. BTN_TOUCH must be |
378 | used to report when a touch is active on the screen. | |
379 | BTN_{MOUSE,LEFT,MIDDLE,RIGHT} must not be reported as the result of touch | |
380 | contact. BTN_TOOL_<name> events should be reported where possible. | |
381 | ||
d04df023 HR |
382 | For new hardware, INPUT_PROP_DIRECT should be set. |
383 | ||
acbdca8b MCC |
384 | Trackpads |
385 | --------- | |
386 | ||
b1e064b8 CD |
387 | Legacy trackpads that only provide relative position information must report |
388 | events like mice described above. | |
389 | ||
390 | Trackpads that provide absolute touch position must report ABS_{X,Y} for the | |
391 | location of the touch. BTN_TOUCH should be used to report when a touch is active | |
392 | on the trackpad. Where multi-finger support is available, BTN_TOOL_<name> should | |
393 | be used to report the number of touches active on the trackpad. | |
394 | ||
d04df023 HR |
395 | For new hardware, INPUT_PROP_POINTER should be set. |
396 | ||
acbdca8b MCC |
397 | Tablets |
398 | ------- | |
399 | ||
b1e064b8 CD |
400 | BTN_TOOL_<name> events must be reported when a stylus or other tool is active on |
401 | the tablet. ABS_{X,Y} must be reported with the location of the tool. BTN_TOUCH | |
402 | should be used to report when the tool is in contact with the tablet. | |
403 | BTN_{STYLUS,STYLUS2} should be used to report buttons on the tool itself. Any | |
404 | button may be used for buttons on the tablet except BTN_{MOUSE,LEFT}. | |
405 | BTN_{0,1,2,etc} are good generic codes for unlabeled buttons. Do not use | |
406 | meaningful buttons, like BTN_FORWARD, unless the button is labeled for that | |
407 | purpose on the device. | |
d04df023 HR |
408 | |
409 | For new hardware, both INPUT_PROP_DIRECT and INPUT_PROP_POINTER should be set. |