patch-2.3.99-pre4 linux/Documentation/usb/input.txt

• Lines: 295
• Date: Wed Apr 5 16:58:38 2000
• Orig file: v2.3.99-pre3/linux/Documentation/usb/input.txt
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.99-pre3/linux/Documentation/usb/input.txt linux/Documentation/usb/input.txt
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+			  Linux Input drivers v0.9
+		 (c) 1999 Vojtech Pavlik <vojtech@suse.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@suse.cz>, or by paper mail: Vojtech Pavlik,
+Ucitelska 1576, 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. However, in the current kernels, although it's
+possibilities are much bigger, it's limited to USB devices only. This is
+also why it resides in the drivers/usb subdirectory.
+
+  The center of the input drivers is the input.o 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.o module.
+
+1.2 Event handlers
+~~~~~~~~~~~~~~~~~~
+  These modules get events from input.o 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.o
+	mousedev.o
+	keybdev.o
+	usbcore.o
+	usb-[uo]hci.o
+	hid.o
+
+  After this, the USB keyboard will work straight away, and the USB mouse
+will be available as a character device on major 13, minor 32:
+
+	crw-r--r--   1 root     root      13,  32 Mar 28 22:45 mouse0
+
+  This device, has to be created, unless you use devfs, in which case it's
+created automatically. The commands to do that are:
+
+	cd /dev
+	mkdir input
+	mknod input/mouse0 c 13 32
+
+  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/mouse0
+
+  And in X:
+
+	Section "Pointer"
+	    Protocol    "ImPS/2"
+	    Device      "/dev/input/mouse0"
+	    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 hid.c
+~~~~~~~~~~~
+  Hid.c 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. The driver
+doesn't support these yet, and a new, non-event interface should be designed
+for them. If you have any of these devices (I don't), feel free to design
+something and if it's good, it'll get into the driver.
+
+  The usage of the hid.o 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.c and send me the syslog traces.
+
+3.1.2 usbmouse.c
+~~~~~~~~~~~~~~~~
+  For embedded systems, for mice with broken HID descriptors and just any
+other use when the big hid.c wouldn't be a good choice, there is the
+usbmouse.c 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 hid.c
+instead.
+
+3.1.3 usbkbd.c
+~~~~~~~~~~~~~~
+  Much like usbmouse.c, this module talks to keyboards with a simpplified
+HIDBP protocol. It's smaller, but doesn't support any extra special keys.
+Use hid.c instead if there isn't any special reason to use this.
+
+3.1.4 wacom.c
+~~~~~~~~~~~~~
+  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 wmforce.c
+~~~~~~~~~~~~~~~
+  A driver for the Logitech WingMan Force joysticks, when connected via the
+USB port. It works quite well, but there is no force feedback support yet,
+because the interface to do that is a trade secret of Immersion Corp, and
+even Logitech can't disclose it.
+
+  Support for Logitech WingMan Force Wheel isn't present in this driver, but
+if someone has the device, and is willing to cooperate, it should be a
+matter of a couple days to add it.
+
+3.2 Event handlers
+~~~~~~~~~~~~~~~~~~
+  Event handlers distrubite the events from the devices to userland and
+kernel, as needed.
+
+3.2.1 keybdev.c
+~~~~~~~~~~~~~~~
+  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.c
+~~~~~~~~~~~~~~~~
+  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.c
+
+  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
+
+and so on, up to mouse31. Each is assigned to a single mouse or digitizer,
+unless CONFIG_INPUT_MOUSEDEV_MIX is set. In that case all mice and
+digitizers share a single character device, mouse0, and even when none are
+connected, mouse0 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 it's movement is sent to X via a virtual PS/2
+mouse.
+
+  Mousedev.c will generate either PS/2, ImPS/2 (microsoft intellimouse) or
+GenPS/2 (genius netmouse/netscroll) protocols, depending on what the program
+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 GenPS/2 if you want to use
+extra (up to 5) buttons. I'm not sure how much is GenPS/2 supported in X,
+though.
+
+3.2.3 joydev.c
+~~~~~~~~~~~~~~
+  Joydev implements v0.x and v1.x Linux joystick api, much like
+drivers/char/joystick/joystick.c. See joystick-api.txt in the Documentation
+subdirectory for details. Joydev does it on top of the input subsystem,
+though. As soon as any USB 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.c
+~~~~~~~~~~~~~
+  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
+
+3. Contacts
+~~~~~~~~~~~
+  This effort has it's home page at:
+
+	http://www.suse.cz/development/input/
+
+You'll find both the latest HID driver and the complete Input driver there.
+There is also a mailing list for this:
+
+	majordomo@atrey.karlin.mff.cuni.cz
+
+Send "subscribe linux-input" to subscribe to it.
+
+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/joystick.txt).
+
+  You can test the event devics with the 'evtest' utitily available on the
+input driver homepage (see the URL above).
+
+5. Event interface
+~~~~~~~~~~~~~~~~~~
+  Should you want to add event device support into any application (X, gpm,
+svgalib ...) I <vojtech@suse.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/inputX 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.