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Linus Torvalds1da177e2005-04-16 15:20:36 -07001 Linux Input drivers v1.0
2 (c) 1999-2001 Vojtech Pavlik <vojtech@ucw.cz>
3 Sponsored by SuSE
Linus Torvalds1da177e2005-04-16 15:20:36 -07004----------------------------------------------------------------------------
5
60. Disclaimer
7~~~~~~~~~~~~~
8 This program is free software; you can redistribute it and/or modify it
9under the terms of the GNU General Public License as published by the Free
10Software Foundation; either version 2 of the License, or (at your option)
11any later version.
12
13 This program is distributed in the hope that it will be useful, but
14WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
16more details.
17
18 You should have received a copy of the GNU General Public License along
19with this program; if not, write to the Free Software Foundation, Inc., 59
20Temple Place, Suite 330, Boston, MA 02111-1307 USA
21
22 Should you need to contact me, the author, you can do so either by e-mail
23- mail your message to <vojtech@ucw.cz>, or by paper mail: Vojtech Pavlik,
24Simunkova 1594, Prague 8, 182 00 Czech Republic
25
26 For your convenience, the GNU General Public License version 2 is included
27in the package: See the file COPYING.
28
291. Introduction
30~~~~~~~~~~~~~~~
31 This is a collection of drivers that is designed to support all input
32devices under Linux. While it is currently used only on for USB input
33devices, future use (say 2.5/2.6) is expected to expand to replace
34most of the existing input system, which is why it lives in
35drivers/input/ instead of drivers/usb/.
36
37 The centre of the input drivers is the input module, which must be
38loaded before any other of the input modules - it serves as a way of
39communication between two groups of modules:
40
411.1 Device drivers
42~~~~~~~~~~~~~~~~~~
43 These modules talk to the hardware (for example via USB), and provide
44events (keystrokes, mouse movements) to the input module.
45
461.2 Event handlers
47~~~~~~~~~~~~~~~~~~
48 These modules get events from input and pass them where needed via
49various interfaces - keystrokes to the kernel, mouse movements via a
50simulated PS/2 interface to GPM and X and so on.
51
522. Simple Usage
53~~~~~~~~~~~~~~~
54 For the most usual configuration, with one USB mouse and one USB keyboard,
55you'll have to load the following modules (or have them built in to the
56kernel):
57
58 input
59 mousedev
60 keybdev
61 usbcore
62 uhci_hcd or ohci_hcd or ehci_hcd
63 usbhid
64
65 After this, the USB keyboard will work straight away, and the USB mouse
66will be available as a character device on major 13, minor 63:
67
68 crw-r--r-- 1 root root 13, 63 Mar 28 22:45 mice
69
Adrian Bunkbf6ee0a2006-10-03 22:17:48 +020070 This device has to be created.
71 The commands to create it by hand are:
Linus Torvalds1da177e2005-04-16 15:20:36 -070072
73 cd /dev
74 mkdir input
75 mknod input/mice c 13 63
76
77 After that you have to point GPM (the textmode mouse cut&paste tool) and
78XFree to this device to use it - GPM should be called like:
79
80 gpm -t ps2 -m /dev/input/mice
81
82 And in X:
83
84 Section "Pointer"
85 Protocol "ImPS/2"
86 Device "/dev/input/mice"
87 ZAxisMapping 4 5
88 EndSection
89
90 When you do all of the above, you can use your USB mouse and keyboard.
91
923. Detailed Description
93~~~~~~~~~~~~~~~~~~~~~~~
943.1 Device drivers
95~~~~~~~~~~~~~~~~~~
96 Device drivers are the modules that generate events. The events are
97however not useful without being handled, so you also will need to use some
98of the modules from section 3.2.
99
1003.1.1 usbhid
101~~~~~~~~~~~~
102 usbhid is the largest and most complex driver of the whole suite. It
103handles all HID devices, and because there is a very wide variety of them,
104and because the USB HID specification isn't simple, it needs to be this big.
105
106 Currently, it handles USB mice, joysticks, gamepads, steering wheels
107keyboards, trackballs and digitizers.
108
109 However, USB uses HID also for monitor controls, speaker controls, UPSs,
110LCDs and many other purposes.
111
112 The monitor and speaker controls should be easy to add to the hid/input
113interface, but for the UPSs and LCDs it doesn't make much sense. For this,
114the hiddev interface was designed. See Documentation/usb/hiddev.txt
115for more information about it.
116
117 The usage of the usbhid module is very simple, it takes no parameters,
118detects everything automatically and when a HID device is inserted, it
119detects it appropriately.
120
121 However, because the devices vary wildly, you might happen to have a
122device that doesn't work well. In that case #define DEBUG at the beginning
123of hid-core.c and send me the syslog traces.
124
1253.1.2 usbmouse
126~~~~~~~~~~~~~~
127 For embedded systems, for mice with broken HID descriptors and just any
128other use when the big usbhid wouldn't be a good choice, there is the
129usbmouse driver. It handles USB mice only. It uses a simpler HIDBP
130protocol. This also means the mice must support this simpler protocol. Not
131all do. If you don't have any strong reason to use this module, use usbhid
132instead.
133
1343.1.3 usbkbd
135~~~~~~~~~~~~
136 Much like usbmouse, this module talks to keyboards with a simplified
137HIDBP protocol. It's smaller, but doesn't support any extra special keys.
138Use usbhid instead if there isn't any special reason to use this.
139
1403.1.4 wacom
141~~~~~~~~~~~
142 This is a driver for Wacom Graphire and Intuos tablets. Not for Wacom
143PenPartner, that one is handled by the HID driver. Although the Intuos and
144Graphire tablets claim that they are HID tablets as well, they are not and
145thus need this specific driver.
146
1473.1.5 iforce
148~~~~~~~~~~~~
149 A driver for I-Force joysticks and wheels, both over USB and RS232.
150It includes ForceFeedback support now, even though Immersion
151Corp. considers the protocol a trade secret and won't disclose a word
152about it.
153
1543.2 Event handlers
155~~~~~~~~~~~~~~~~~~
Matt LaPlantefff92892006-10-03 22:47:42 +0200156 Event handlers distribute the events from the devices to userland and
Linus Torvalds1da177e2005-04-16 15:20:36 -0700157kernel, as needed.
158
1593.2.1 keybdev
160~~~~~~~~~~~~~
161 keybdev is currently a rather ugly hack that translates the input
162events into architecture-specific keyboard raw mode (Xlated AT Set2 on
163x86), and passes them into the handle_scancode function of the
164keyboard.c module. This works well enough on all architectures that
165keybdev can generate rawmode on, other architectures can be added to
166it.
167
168 The right way would be to pass the events to keyboard.c directly,
169best if keyboard.c would itself be an event handler. This is done in
170the input patch, available on the webpage mentioned below.
171
1723.2.2 mousedev
173~~~~~~~~~~~~~~
174 mousedev is also a hack to make programs that use mouse input
175work. It takes events from either mice or digitizers/tablets and makes
176a PS/2-style (a la /dev/psaux) mouse device available to the
177userland. Ideally, the programs could use a more reasonable interface,
178for example evdev
179
180 Mousedev devices in /dev/input (as shown above) are:
181
182 crw-r--r-- 1 root root 13, 32 Mar 28 22:45 mouse0
183 crw-r--r-- 1 root root 13, 33 Mar 29 00:41 mouse1
184 crw-r--r-- 1 root root 13, 34 Mar 29 00:41 mouse2
185 crw-r--r-- 1 root root 13, 35 Apr 1 10:50 mouse3
186 ...
187 ...
188 crw-r--r-- 1 root root 13, 62 Apr 1 10:50 mouse30
189 crw-r--r-- 1 root root 13, 63 Apr 1 10:50 mice
190
191Each 'mouse' device is assigned to a single mouse or digitizer, except
192the last one - 'mice'. This single character device is shared by all
193mice and digitizers, and even if none are connected, the device is
194present. This is useful for hotplugging USB mice, so that programs
195can open the device even when no mice are present.
196
197 CONFIG_INPUT_MOUSEDEV_SCREEN_[XY] in the kernel configuration are
198the size of your screen (in pixels) in XFree86. This is needed if you
199want to use your digitizer in X, because its movement is sent to X
200via a virtual PS/2 mouse and thus needs to be scaled
201accordingly. These values won't be used if you use a mouse only.
202
203 Mousedev will generate either PS/2, ImPS/2 (Microsoft IntelliMouse) or
204ExplorerPS/2 (IntelliMouse Explorer) protocols, depending on what the
205program reading the data wishes. You can set GPM and X to any of
206these. You'll need ImPS/2 if you want to make use of a wheel on a USB
207mouse and ExplorerPS/2 if you want to use extra (up to 5) buttons.
208
2093.2.3 joydev
210~~~~~~~~~~~~
211 Joydev implements v0.x and v1.x Linux joystick api, much like
212drivers/char/joystick/joystick.c used to in earlier versions. See
213joystick-api.txt in the Documentation subdirectory for details. As
214soon as any joystick is connected, it can be accessed in /dev/input
215on:
216
217 crw-r--r-- 1 root root 13, 0 Apr 1 10:50 js0
218 crw-r--r-- 1 root root 13, 1 Apr 1 10:50 js1
219 crw-r--r-- 1 root root 13, 2 Apr 1 10:50 js2
220 crw-r--r-- 1 root root 13, 3 Apr 1 10:50 js3
221 ...
222
223And so on up to js31.
224
2253.2.4 evdev
226~~~~~~~~~~~
227 evdev is the generic input event interface. It passes the events
228generated in the kernel straight to the program, with timestamps. The
229API is still evolving, but should be useable now. It's described in
230section 5.
231
Paolo Ornati670e9f32006-10-03 22:57:56 +0200232 This should be the way for GPM and X to get keyboard and mouse
Linus Torvalds1da177e2005-04-16 15:20:36 -0700233events. It allows for multihead in X without any specific multihead
234kernel support. The event codes are the same on all architectures and
235are hardware independent.
236
237 The devices are in /dev/input:
238
239 crw-r--r-- 1 root root 13, 64 Apr 1 10:49 event0
240 crw-r--r-- 1 root root 13, 65 Apr 1 10:50 event1
241 crw-r--r-- 1 root root 13, 66 Apr 1 10:50 event2
242 crw-r--r-- 1 root root 13, 67 Apr 1 10:50 event3
243 ...
244
245And so on up to event31.
246
2474. Verifying if it works
248~~~~~~~~~~~~~~~~~~~~~~~~
249 Typing a couple keys on the keyboard should be enough to check that
250a USB keyboard works and is correctly connected to the kernel keyboard
251driver.
252
253 Doing a cat /dev/input/mouse0 (c, 13, 32) will verify that a mouse
254is also emulated, characters should appear if you move it.
255
256 You can test the joystick emulation with the 'jstest' utility,
257available in the joystick package (see Documentation/input/joystick.txt).
258
259 You can test the event devices with the 'evtest' utility available
260in the LinuxConsole project CVS archive (see the URL below).
261
2625. Event interface
263~~~~~~~~~~~~~~~~~~
264 Should you want to add event device support into any application (X, gpm,
265svgalib ...) I <vojtech@ucw.cz> will be happy to provide you any help I
266can. Here goes a description of the current state of things, which is going
267to be extended, but not changed incompatibly as time goes:
268
269 You can use blocking and nonblocking reads, also select() on the
270/dev/input/eventX devices, and you'll always get a whole number of input
271events on a read. Their layout is:
272
273struct input_event {
274 struct timeval time;
275 unsigned short type;
276 unsigned short code;
277 unsigned int value;
278};
279
280 'time' is the timestamp, it returns the time at which the event happened.
Matt LaPlante2fe0ae72006-10-03 22:50:39 +0200281Type is for example EV_REL for relative moment, REL_KEY for a keypress or
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282release. More types are defined in include/linux/input.h.
283
284 'code' is event code, for example REL_X or KEY_BACKSPACE, again a complete
285list is in include/linux/input.h.
286
287 'value' is the value the event carries. Either a relative change for
288EV_REL, absolute new value for EV_ABS (joysticks ...), or 0 for EV_KEY for
289release, 1 for keypress and 2 for autorepeat.
290