Add section on input devices.
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+<!--
+ Copyright 2011 The Android Open Source Project
+
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+-->
+
+# Migration Guide #
+
+This document contains a few helpful tips when migrating to new Android releases.
+
+## Migrating to Android Gingerbread 2.3 ##
+
+In Gingerbread, we added the concept of input device configuration files
+(also referred to as input device calibration files in this release).
+
+Make sure to provide an input device configuration file for all touch screens.
+In particular, it is worth spending time providing a calibration reference for
+touch size information.
+
+## Migrating to Android Honeycomb 3.0 ##
+
+In Honeycomb, we revised the key character map file format and started making
+greater use of input device configuration files. We also added support for full
+PC-style keyboards and introduced a new "Generic" key map, which
+replaced the older emulator-specific "qwerty" key map (which was never
+intended to be used as a general-purpose key map.)
+
+Make sure to update all of your key character map files to use the new syntax.
+
+If your peripherals relied on the old "qwerty" key map, then you
+may need to provide new device-specific key maps to emulate the old behavior.
+You should create a new key map for each device identified either by
+USB product id / vendor id or by device name.
+
+It is especially important to provide key character map files for all special
+function input devices. These files should simple contain a line to set
+the keyboard type to `SPECIAL_FUNCTION`.
+
+A good way to ensure that all built-in input devices are appropriately configured
+is to run [Dumpsys](/tech/input/dumpsys.html) and look for devices that
+are inappropriately using `Generic.kcm`.
+
+## Migrating to Android Honeycomb 3.2 ##
+
+In Honeycomb 3.2, we added support for joysticks and extended the key layout file
+format to enable joystick axis mapping.
+
+## Migrating to Android Ice Cream Sandwich 4.0 ##
+
+In Ice Cream Sandwich 4.0, we changed the device driver requirements for touch screens
+to follow the standard Linux multitouch input protocol and added support for
+protocol "B". We also support digitizer tablets and stylus-based touch devices.
+
+You will probably need to update your input device driver to implement the Linux
+multitouch input protocol correctly according to the standard.
+
+You will also need to update your input device configuration files because some
+properties have been changed to be simpler and more systematic.
+
+Refer to [Touch Devices](/tech/input/touch-devices.html) for more details about
+driver requirements.