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