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diff --git a/kernel/Documentation/input/input.txt b/kernel/Documentation/input/input.txt new file mode 100644 index 000000000..0acfddbe2 --- /dev/null +++ b/kernel/Documentation/input/input.txt @@ -0,0 +1,290 @@ + Linux Input drivers v1.0 + (c) 1999-2001 Vojtech Pavlik <vojtech@ucw.cz> + Sponsored by SuSE +---------------------------------------------------------------------------- + +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 +kernel): + + 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. + The commands to 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/hid/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 +instead. + +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 distribute 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 +it. + + 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 +on: + + 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 usable now. It's described in +section 5. + + This should be the way for GPM and X to get keyboard and 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 +driver. + + 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 moment, EV_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. + |