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+ Linux Input drivers v1.0
+ (c) 1999-2001 Vojtech Pavlik <vojtech@ucw.cz>
+ Sponsored by SuSE
+ $Id: input.txt,v 1.8 2002/05/29 03:15:01 bradleym Exp $
+0. Disclaimer
+ This program is free software; you can redistribute it and/or modify it
+under the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 2 of the License, or (at your option)
+any later version.
+ This program is distributed in the hope that it will be useful, but
+WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+more details.
+ You should have received a copy of the GNU General Public License along
+with this program; if not, write to the Free Software Foundation, Inc., 59
+Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ Should you need to contact me, the author, you can do so either by e-mail
+- mail your message to <vojtech@ucw.cz>, or by paper mail: Vojtech Pavlik,
+Simunkova 1594, Prague 8, 182 00 Czech Republic
+ For your convenience, the GNU General Public License version 2 is included
+in the package: See the file COPYING.
+1. Introduction
+ This is a collection of drivers that is designed to support all input
+devices under Linux. While it is currently used only on for USB input
+devices, future use (say 2.5/2.6) is expected to expand to replace
+most of the existing input system, which is why it lives in
+drivers/input/ instead of drivers/usb/.
+ The centre of the input drivers is the input module, which must be
+loaded before any other of the input modules - it serves as a way of
+communication between two groups of modules:
+1.1 Device drivers
+ These modules talk to the hardware (for example via USB), and provide
+events (keystrokes, mouse movements) to the input module.
+1.2 Event handlers
+ These modules get events from input and pass them where needed via
+various interfaces - keystrokes to the kernel, mouse movements via a
+simulated PS/2 interface to GPM and X and so on.
+2. Simple Usage
+ For the most usual configuration, with one USB mouse and one USB keyboard,
+you'll have to load the following modules (or have them built in to the
+ input
+ mousedev
+ keybdev
+ usbcore
+ uhci_hcd or ohci_hcd or ehci_hcd
+ usbhid
+ After this, the USB keyboard will work straight away, and the USB mouse
+will be available as a character device on major 13, minor 63:
+ crw-r--r-- 1 root root 13, 63 Mar 28 22:45 mice
+ This device has to be created, unless you use devfs, in which case it's
+created automatically. The commands to do create it by hand are:
+ cd /dev
+ mkdir input
+ mknod input/mice c 13 63
+ After that you have to point GPM (the textmode mouse cut&paste tool) and
+XFree to this device to use it - GPM should be called like:
+ gpm -t ps2 -m /dev/input/mice
+ And in X:
+ Section "Pointer"
+ Protocol "ImPS/2"
+ Device "/dev/input/mice"
+ ZAxisMapping 4 5
+ EndSection
+ When you do all of the above, you can use your USB mouse and keyboard.
+3. Detailed Description
+3.1 Device drivers
+ Device drivers are the modules that generate events. The events are
+however not useful without being handled, so you also will need to use some
+of the modules from section 3.2.
+3.1.1 usbhid
+ usbhid is the largest and most complex driver of the whole suite. It
+handles all HID devices, and because there is a very wide variety of them,
+and because the USB HID specification isn't simple, it needs to be this big.
+ Currently, it handles USB mice, joysticks, gamepads, steering wheels
+keyboards, trackballs and digitizers.
+ However, USB uses HID also for monitor controls, speaker controls, UPSs,
+LCDs and many other purposes.
+ The monitor and speaker controls should be easy to add to the hid/input
+interface, but for the UPSs and LCDs it doesn't make much sense. For this,
+the hiddev interface was designed. See Documentation/usb/hiddev.txt
+for more information about it.
+ The usage of the usbhid module is very simple, it takes no parameters,
+detects everything automatically and when a HID device is inserted, it
+detects it appropriately.
+ However, because the devices vary wildly, you might happen to have a
+device that doesn't work well. In that case #define DEBUG at the beginning
+of hid-core.c and send me the syslog traces.
+3.1.2 usbmouse
+ For embedded systems, for mice with broken HID descriptors and just any
+other use when the big usbhid wouldn't be a good choice, there is the
+usbmouse driver. It handles USB mice only. It uses a simpler HIDBP
+protocol. This also means the mice must support this simpler protocol. Not
+all do. If you don't have any strong reason to use this module, use usbhid
+3.1.3 usbkbd
+ Much like usbmouse, this module talks to keyboards with a simplified
+HIDBP protocol. It's smaller, but doesn't support any extra special keys.
+Use usbhid instead if there isn't any special reason to use this.
+3.1.4 wacom
+ This is a driver for Wacom Graphire and Intuos tablets. Not for Wacom
+PenPartner, that one is handled by the HID driver. Although the Intuos and
+Graphire tablets claim that they are HID tablets as well, they are not and
+thus need this specific driver.
+3.1.5 iforce
+ A driver for I-Force joysticks and wheels, both over USB and RS232.
+It includes ForceFeedback support now, even though Immersion
+Corp. considers the protocol a trade secret and won't disclose a word
+about it.
+3.2 Event handlers
+ Event handlers distrubite the events from the devices to userland and
+kernel, as needed.
+3.2.1 keybdev
+ keybdev is currently a rather ugly hack that translates the input
+events into architecture-specific keyboard raw mode (Xlated AT Set2 on
+x86), and passes them into the handle_scancode function of the
+keyboard.c module. This works well enough on all architectures that
+keybdev can generate rawmode on, other architectures can be added to
+ The right way would be to pass the events to keyboard.c directly,
+best if keyboard.c would itself be an event handler. This is done in
+the input patch, available on the webpage mentioned below.
+3.2.2 mousedev
+ mousedev is also a hack to make programs that use mouse input
+work. It takes events from either mice or digitizers/tablets and makes
+a PS/2-style (a la /dev/psaux) mouse device available to the
+userland. Ideally, the programs could use a more reasonable interface,
+for example evdev
+ Mousedev devices in /dev/input (as shown above) are:
+ crw-r--r-- 1 root root 13, 32 Mar 28 22:45 mouse0
+ crw-r--r-- 1 root root 13, 33 Mar 29 00:41 mouse1
+ crw-r--r-- 1 root root 13, 34 Mar 29 00:41 mouse2
+ crw-r--r-- 1 root root 13, 35 Apr 1 10:50 mouse3
+ ...
+ ...
+ crw-r--r-- 1 root root 13, 62 Apr 1 10:50 mouse30
+ crw-r--r-- 1 root root 13, 63 Apr 1 10:50 mice
+Each 'mouse' device is assigned to a single mouse or digitizer, except
+the last one - 'mice'. This single character device is shared by all
+mice and digitizers, and even if none are connected, the device is
+present. This is useful for hotplugging USB mice, so that programs
+can open the device even when no mice are present.
+ CONFIG_INPUT_MOUSEDEV_SCREEN_[XY] in the kernel configuration are
+the size of your screen (in pixels) in XFree86. This is needed if you
+want to use your digitizer in X, because its movement is sent to X
+via a virtual PS/2 mouse and thus needs to be scaled
+accordingly. These values won't be used if you use a mouse only.
+ Mousedev will generate either PS/2, ImPS/2 (Microsoft IntelliMouse) or
+ExplorerPS/2 (IntelliMouse Explorer) protocols, depending on what the
+program reading the data wishes. You can set GPM and X to any of
+these. You'll need ImPS/2 if you want to make use of a wheel on a USB
+mouse and ExplorerPS/2 if you want to use extra (up to 5) buttons.
+3.2.3 joydev
+ Joydev implements v0.x and v1.x Linux joystick api, much like
+drivers/char/joystick/joystick.c used to in earlier versions. See
+joystick-api.txt in the Documentation subdirectory for details. As
+soon as any joystick is connected, it can be accessed in /dev/input
+ crw-r--r-- 1 root root 13, 0 Apr 1 10:50 js0
+ crw-r--r-- 1 root root 13, 1 Apr 1 10:50 js1
+ crw-r--r-- 1 root root 13, 2 Apr 1 10:50 js2
+ crw-r--r-- 1 root root 13, 3 Apr 1 10:50 js3
+ ...
+And so on up to js31.
+3.2.4 evdev
+ evdev is the generic input event interface. It passes the events
+generated in the kernel straight to the program, with timestamps. The
+API is still evolving, but should be useable now. It's described in
+section 5.
+ This should be the way for GPM and X to get keyboard and mouse mouse
+events. It allows for multihead in X without any specific multihead
+kernel support. The event codes are the same on all architectures and
+are hardware independent.
+ The devices are in /dev/input:
+ crw-r--r-- 1 root root 13, 64 Apr 1 10:49 event0
+ crw-r--r-- 1 root root 13, 65 Apr 1 10:50 event1
+ crw-r--r-- 1 root root 13, 66 Apr 1 10:50 event2
+ crw-r--r-- 1 root root 13, 67 Apr 1 10:50 event3
+ ...
+And so on up to event31.
+4. Verifying if it works
+ Typing a couple keys on the keyboard should be enough to check that
+a USB keyboard works and is correctly connected to the kernel keyboard
+ Doing a cat /dev/input/mouse0 (c, 13, 32) will verify that a mouse
+is also emulated, characters should appear if you move it.
+ You can test the joystick emulation with the 'jstest' utility,
+available in the joystick package (see Documentation/input/joystick.txt).
+ You can test the event devices with the 'evtest' utility available
+in the LinuxConsole project CVS archive (see the URL below).
+5. Event interface
+ Should you want to add event device support into any application (X, gpm,
+svgalib ...) I <vojtech@ucw.cz> will be happy to provide you any help I
+can. Here goes a description of the current state of things, which is going
+to be extended, but not changed incompatibly as time goes:
+ You can use blocking and nonblocking reads, also select() on the
+/dev/input/eventX devices, and you'll always get a whole number of input
+events on a read. Their layout is:
+struct input_event {
+ struct timeval time;
+ unsigned short type;
+ unsigned short code;
+ unsigned int value;
+ 'time' is the timestamp, it returns the time at which the event happened.
+Type is for example EV_REL for relative momement, REL_KEY for a keypress or
+release. More types are defined in include/linux/input.h.
+ 'code' is event code, for example REL_X or KEY_BACKSPACE, again a complete
+list is in include/linux/input.h.
+ 'value' is the value the event carries. Either a relative change for
+EV_REL, absolute new value for EV_ABS (joysticks ...), or 0 for EV_KEY for
+release, 1 for keypress and 2 for autorepeat.
+6. Contacts
+ This effort has its home page at:
+ http://www.suse.cz/development/input/
+You'll find both the latest HID driver and the complete Input driver
+there as well as information how to access the CVS repository for
+latest revisions of the drivers.
+ There is also a mailing list for this:
+ majordomo@atrey.karlin.mff.cuni.cz
+Send "subscribe linux-input" to subscribe to it.
+The input changes are also being worked on as part of the LinuxConsole
+project, see:
+ http://sourceforge.net/projects/linuxconsole/