Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

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+.. include:: <isonum.txt>
+
+============
+Introduction
+============
+
+:Copyright: |copy| 1999-2001 Vojtech Pavlik <vojtech@ucw.cz> - Sponsored by SuSE
+
+Architecture
+============
+
+Input subsystem  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 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 moment, 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.