282 lines
8.9 KiB
ReStructuredText
282 lines
8.9 KiB
ReStructuredText
|
.. include:: <isonum.txt>
|
||
|
|
|
||
|
|
============
|
||
|
|
Introduction
|
||
|
|
============
|
||
|
|
|
||
|
|
:Copyright: |copy| 1999-2001 Vojtech Pavlik <vojtech@ucw.cz> - Sponsored by SuSE
|
||
|
|
|
||
|
|
Architecture
|
||
|
|
============
|
||
|
|
|
||
|
|
Input subsystem is a collection of drivers that is designed to support
|
||
|
|
all input devices under Linux. Most of the drivers reside in
|
||
|
|
drivers/input, although quite a few live in drivers/hid and
|
||
|
|
drivers/platform.
|
||
|
|
|
||
|
|
The core of the input subsystem 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:
|
||
|
|
|
||
|
|
Device drivers
|
||
|
|
--------------
|
||
|
|
|
||
|
|
These modules talk to the hardware (for example via USB), and provide
|
||
|
|
events (keystrokes, mouse movements) to the input module.
|
||
|
|
|
||
|
|
Event handlers
|
||
|
|
--------------
|
||
|
|
|
||
|
|
These modules get events from input core 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.
|
||
|
|
|
||
|
|
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
|
||
|
|
usbcore
|
||
|
|
uhci_hcd or ohci_hcd or ehci_hcd
|
||
|
|
usbhid
|
||
|
|
hid_generic
|
||
|
|
|
||
|
|
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 is usually created automatically by the system. 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.
|
||
|
|
|
||
|
|
Detailed Description
|
||
|
|
====================
|
||
|
|
|
||
|
|
Event handlers
|
||
|
|
--------------
|
||
|
|
|
||
|
|
Event handlers distribute the events from the devices to userspace and
|
||
|
|
in-kernel consumers, as needed.
|
||
|
|
|
||
|
|
evdev
|
||
|
|
~~~~~
|
||
|
|
|
||
|
|
``evdev`` is the generic input event interface. It passes the events
|
||
|
|
generated in the kernel straight to the program, with timestamps. The
|
||
|
|
event codes are the same on all architectures and are hardware
|
||
|
|
independent.
|
||
|
|
|
||
|
|
This is the preferred interface for userspace to consume user
|
||
|
|
input, and all clients are encouraged to use it.
|
||
|
|
|
||
|
|
See :ref:`event-interface` for notes on API.
|
||
|
|
|
||
|
|
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
|
||
|
|
...
|
||
|
|
|
||
|
|
There are two ranges of minors: 64 through 95 is the static legacy
|
||
|
|
range. If there are more than 32 input devices in a system, additional
|
||
|
|
evdev nodes are created with minors starting with 256.
|
||
|
|
|
||
|
|
keyboard
|
||
|
|
~~~~~~~~
|
||
|
|
|
||
|
|
``keyboard`` is in-kernel input handler and is a part of VT code. It
|
||
|
|
consumes keyboard keystrokes and handles user input for VT consoles.
|
||
|
|
|
||
|
|
mousedev
|
||
|
|
~~~~~~~~
|
||
|
|
|
||
|
|
``mousedev`` is a hack to make legacy 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.
|
||
|
|
|
||
|
|
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 older programs
|
||
|
|
that do not handle hotplug 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.
|
||
|
|
|
||
|
|
joydev
|
||
|
|
~~~~~~
|
||
|
|
|
||
|
|
``joydev`` implements v0.x and v1.x Linux joystick API. See
|
||
|
|
:ref:`joystick-api` 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 in legacy range, and additional nodes with minors
|
||
|
|
above 256 if there are more joystick devices.
|
||
|
|
|
||
|
|
Device drivers
|
||
|
|
--------------
|
||
|
|
|
||
|
|
Device drivers are the modules that generate events.
|
||
|
|
|
||
|
|
hid-generic
|
||
|
|
~~~~~~~~~~~
|
||
|
|
|
||
|
|
``hid-generic`` is one of 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.rst
|
||
|
|
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.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
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.
|
||
|
|
|
||
|
|
psmouse
|
||
|
|
~~~~~~~
|
||
|
|
|
||
|
|
This is driver for all flavors of pointing devices using PS/2
|
||
|
|
protocol, including Synaptics and ALPS touchpads, Intellimouse
|
||
|
|
Explorer devices, Logitech PS/2 mice and so on.
|
||
|
|
|
||
|
|
atkbd
|
||
|
|
~~~~~
|
||
|
|
|
||
|
|
This is driver for PS/2 (AT) keyboards.
|
||
|
|
|
||
|
|
iforce
|
||
|
|
~~~~~~
|
||
|
|
|
||
|
|
A driver for I-Force joysticks and wheels, both over USB and RS232.
|
||
|
|
It includes Force Feedback support now, even though Immersion
|
||
|
|
Corp. considers the protocol a trade secret and won't disclose a word
|
||
|
|
about it.
|
||
|
|
|
||
|
|
Verifying if it works
|
||
|
|
=====================
|
||
|
|
|
||
|
|
Typing a couple keys on the keyboard should be enough to check that
|
||
|
|
a 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 :ref:`joystick-doc`).
|
||
|
|
|
||
|
|
You can test the event devices with the ``evtest`` utility.
|
||
|
|
|
||
|
|
.. _event-interface:
|
||
|
|
|
||
|
|
Event interface
|
||
|
|
===============
|
||
|
|
|
||
|
|
You can use blocking and nonblocking reads, and 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 movement, EV_KEY for a keypress or
|
||
|
|
release. More types are defined in include/uapi/linux/input-event-codes.h.
|
||
|
|
|
||
|
|
``code`` is event code, for example REL_X or KEY_BACKSPACE, again a complete
|
||
|
|
list is in include/uapi/linux/input-event-codes.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.
|
||
|
|
|
||
|
|
See :ref:`input-event-codes` for more information about various even codes.
|