page.title=Keymaps and Keyboard Input
pdk.version=1.0
doc.type=guide
@jd:body
<div id="qv-wrapper">
<div id="qv">
<h2>In this document</h2>
<a name="toc"/>
<ul>
<li><a href="#androidKeymapFunctionality">Functionality</a></li>
<li><a href="#androidKeymapKeyLayoutMapTitle">Key Layout Map</a></li>
<li><a href="#androidKeymapKeyCharMap">Key Character Map</a></li>
<li><a href="#androidKeymapDriverTemplate">Implementing Your Own Driver (Driver Template)</a></li>
<li><a href="#androidKeymapKeyCharMapSampleImplementation">Sample Implementation</a></li>
</ul>
</div>
</div>
<p>This document describes how keyboard input gets translated into Android actions and how you can customize key layout and key character maps to match the needs of your own device. </p>
<p>Android uses the standard Linux input event device (<code>/dev/event0</code>) and driver as described in the <code>linux/input.h</code> kernel header file. For more information regarding standard Linux input drivers, please see <a href="http://git.kernel.org/?p=linux/kernel/git/stable/linux-2.6.24.y.git;a=blob;f=Documentation/input/input.txt">Linux Input drivers</a> at <a href="http://kernel.org">http://kernel.org</a>.</p>
<a name="androidKeymapFunctionality"></a><h3>Functionality</h3>
<p>Android's input event device is structured around an interrupt or polling routine that captures the device-specific scancode and converts it to a standard form acceptable to Linux (as defined in <code>input.h</code>) before passing it to the kernel with <code>input_event()</code>.</p>
<p>The keymap driver's other primary function is to establish a probe function that sets up the interrupt or polling function, handles hardware initialization, and attaches the driver to the input subsystem with <code>input_register_device()</code>.</p>
<p>The table below describes the steps required to translate from keyboard input to application action: </p>
<table border=1>
<tbody><tr>
<th scope="col">Step</th>
<th scope="col">Action</th>
<th scope="col">Explanation</th>
</tr>
<tr>
<td>1.</td>
<td>Window manager reads key event from Linux keyboard driver. </td>
<td>Events are typically positional. For example, the top-left position on a keypad returns 16 regardless of whether that key is printed with a Q (as on a QWERTY keypad) or an A (as on an AZERTY keypads). This first conversion by the Linux Keyboard Driver yields a scancode (for example, 16).</td>
</tr>
<tr>
<td>2. </td>
<td>Window manager maps scancode to keycode.</td>
<td>When the window manager reads a key event out of the driver, it maps the scancode to a keycode using a key layout map file. Typically, the keycode is the primary symbol screen-printed on a key. For example, <code>KEYCODE_DPAD_CENTER</code> is the center button on the five-way navigation control. Even though ALT + G generates a "?" character, <code>KEYCODE_G</code> is the keycode.</td>
</tr>
<tr>
<td>3. </td>
<td>Window manager sends both the scancode and the keycode to the application.</td>
<td>Both the scancode and keycode are handled by the view with focus.
How the application interprets both depend on the application.</td>
</tr>
</tbody>
</table>
<a name="androidKeymapKeyLayoutMapTitle"></a><h3>Key Layout Map</h3>
<a name="androidKeymapKeyLayoutMapSelection"></a><h4>Selection of a Key Layout Map</h4>
<p>Key layout maps are installed in <code>/system/usr/keylayout</code> and <code>/data/usr/keylayout</code>.</p>
<p>For each keyboard device xxx, set the <code>android.keylayout.xxx</code> system property (see <a href="build_new_device.html">Building New Device</a> for help setting system properties). If you don't specify a keylayout file, Android will default to <code>/system/usr/keylayout/qwerty.kl</code>.</p>
<a name="androidKeymapKeyLayoutMapFileFormat"></a><h4>File Format</h4>
<p>Key layout maps are stored on the device as UTF-8 text files and have the following characteristics:</p>
<p><ul>
<li>Comments: The pound symbol (#) denotes a comment and everything after the pound symbol on a line is ignored.</li>
<li>Whitespace: All empty lines are ignored.</li>
<li>Key definitions: Key definitions follow the syntax <code>key SCANCODE KEYCODE [FLAGS...]</code>, where <code>SCANCODE</code> is a number, <code>KEYCODE</code> is defined in your specific keylayout file (<code>android.keylayout.xxx</code>), and potential <code>FLAGS</code> are defined as follows:
<ul><li>SHIFT: While pressed, the shift key modifier is set</li>
<li>ALT: While pressed, the alt key modifier is set</li>
<li>CAPS: While pressed, the caps lock key modifier is set</li>
<li>WAKE: When this key is pressed while the device is asleep, the device will wake up and the key event gets sent to the app.</li>
<li>WAKE_DROPPED: When this key is pressed while the device is asleep, the device will wake up and the key event does not get sent to the app.</li>
</ul>
</li>
</ul>
</p>
<a name="androidKeymapKeyLayoutMapExample"></a><h4>Example of a Key Layout Map File</h4>
<p>The following code comes from <code>android/src/device/product/generic/tuttle2.kl</code> and is an example of a complete key layout file:</p>
<pre class="prettify">
# Copyright 2007 Google Inc.
key 2 1
key 3 2
key 4 3
key 5 4
key 6 5
key 7 6
key 8 7
key 9 8
key 10 9
key 11 0
key 158 BACK WAKE_DROPPED
key 230 SOFT_RIGHT WAKE
key 60 SOFT_RIGHT WAKE
key 107 ENDCALL WAKE_DROPPED
key 62 ENDCALL WAKE_DROPPED
key 229 MENU WAKE_DROPPED
key 59 MENU WAKE_DROPPED
key 228 POUND
key 227 STAR
key 231 CALL WAKE_DROPPED
key 61 CALL WAKE_DROPPED
key 232 DPAD_CENTER WAKE_DROPPED
key 108 DPAD_DOWN WAKE_DROPPED
key 103 DPAD_UP WAKE_DROPPED
key 102 HOME WAKE
key 105 DPAD_LEFT WAKE_DROPPED
key 106 DPAD_RIGHT WAKE_DROPPED
key 115 VOLUME_UP
key 114 VOLUME_DOWN
key 116 POWER WAKE
key 212 SLASH
key 16 Q
key 17 W
key 18 E
key 19 R
key 20 T
key 21 Y
key 22 U
key 23 I
key 24 O
key 25 P
key 30 A
key 31 S
key 32 D
key 33 F
key 34 G
key 35 H
key 36 J
key 37 K
key 38 L
key 14 DEL
key 44 Z
key 45 X
key 46 C
key 47 V
key 48 B
key 49 N
key 50 M
key 51 COMMA
key 52 PERIOD
key 28 NEWLINE
key 56 ALT_LEFT
key 42 SHIFT_LEFT
key 215 AT
key 57 SPACE
key 53 SLASH
key 127 SYM
key 100 ALT_LEFT
key 399 GRAVE
</pre>
<a name="androidKeymapKeyCharMap"></a><h3>Key Character Map</h3>
<a name="androidKeymapKeyCharMapSelection"></a><h4>Selection of a Key Character Map</h4>
<p>Key character maps are installed in <code>/system/usr/keychars</code> and <code>/data/usr/keychars</code>.</p>
<p>For each keyboard device xxx, set the <code>android.keychar.xxx</code> system property to the full path of the desired keychar file. If you don't specify a keychar file, Android will default to <code>/system/usr/keychar/qwerty.kl</code>.
<a name="androidKeymapKeyCharMapFileFormat"></a><h4>File Format</h4>
<p>Key character maps are stored on the device as binary resources in order to reduce loading time. Key character maps have the following characteristics:</p>
<p><ul>
<li>Comments: The pound symbol (#) denotes a comment and everything after the pound symbol on a line is ignored.</li>
<li>Whitespace: All empty lines are ignored.</li>
<li>Column definitions: Column definitions follow the syntax <code>columns MODIFIERS [...]</code>, where <code>MODIFIERS</code> are defined as follows:
<table border=1 cellpadding=2 cellspacing=0>
<tbody><tr>
<th scope="col">Character in MODIFIERS</th>
<th scope="col">Corresponding bit in the modifiers</th>
</tr>
<tr>
<td>O</td>
<td>no modifiers</td>
</tr>
<tr>
<td>S</td>
<td>MODIFIER_SHIFT</td>
</tr>
<tr>
<td>C</td>
<td>MODIFIER_CONTROL</td>
</tr>
<tr>
<td>L</td>
<td>MODIFIER_CAPS_LOCK</td>
</tr>
<tr>
<td>A</td>
<td>MODIFIER_ALT</td>
</tr>
</table>
</li>
<li>Key definitions: Key definitions have the syntax <code>key SCANCODE CHARACTER [...]</code> where <code>SCANCODE</code> is a number and <code>CHARACTER</code> values are either UTF-8 characters in quotation marks (for example, "a") or a numeric value that <code>strtol</code> can parse.</li>
</ul></p>
<a name="androidKeymapKeyCharMapExample"></a><h4>Example of a Key Character Map File</h4>
<p>The following code comes from <code>android/src/device/product/generic/tuttle2.kcm</code> and represents a complete key character file:</p>
<p>The type line indicates what kind of keyboard your device implements. Possible types include:</p>
<p><ul>
<li><b>NUMERIC</b>: A numeric (12-key) keyboard.</li>
<li><b>Q14</b>: A keyboard that includes all letters but multiple letters per key.</li>
<li><b>QWERTY</b>: A keyboard with all letters and possibly numbers. This option applies to all full keyboard configurations, such as AZERTY.</li>
</ul>
</p>
<pre class="prettify">
# Copyright 2007 Google Inc.
[type=QWERTY]
# keycode base caps fn caps_fn number display_label
A 'a' 'A' '%' 0x00 '%' 'A'
B 'b' 'B' '=' 0x00 '=' 'B'
C 'c' 'C' '8' 0x00E7 '8' 'C'
D 'd' 'D' '5' 0x00 '5' 'D'
E 'e' 'E' '2' 0x0301 '2' 'E'
F 'f' 'F' '6' 0x00A5 '6' 'F'
G 'g' 'G' '-' '_' '-' 'G'
H 'h' 'H' '[' '{' '[' 'H'
I 'i' 'I' '$' 0x0302 '$' 'I'
J 'j' 'J' ']' '}' ']' 'J'
K 'k' 'K' '"' '~' '"' 'K'
L 'l' 'L' ''' '`' ''' 'L'
M 'm' 'M' '>' 0x00 '>' 'M'
N 'n' 'N' '<' 0x0303 '<' 'N'
O 'o' 'O' '(' 0x00 '(' 'O'
P 'p' 'P' ')' 0x00 ')' 'P'
Q 'q' 'Q' '*' 0x0300 '*' 'Q'
R 'r' 'R' '3' 0x20AC '3' 'R'
S 's' 'S' '4' 0x00DF '4' 'S'
T 't' 'T' '+' 0x00A3 '+' 'T'
U 'u' 'U' '&' 0x0308 '&' 'U'
V 'v' 'V' '9' '^' '9' 'V'
W 'w' 'W' '1' 0x00 '1' 'W'
X 'x' 'X' '7' 0xEF00 '7' 'X'
Y 'y' 'Y' '!' 0x00A1 '!' 'Y'
Z 'z' 'Z' '#' 0x00 '#' 'Z'
COMMA ',' ';' ';' '|' ',' ','
PERIOD '.' ':' ':' 0x2026 '.' '.'
AT '@' '0' '0' 0x2022 '0' '@'
SLASH '/' '?' '?' '\' '/' '/'
SPACE 0x20 0x20 0x9 0x9 0x20 0x20
NEWLINE 0xa 0xa 0xa 0xa 0xa 0xa
# on pc keyboards
TAB 0x9 0x9 0x9 0x9 0x9 0x9
0 '0' ')' ')' ')' '0' '0'
1 '1' '!' '!' '!' '1' '1'
2 '2' '@' '@' '@' '2' '2'
3 '3' '#' '#' '#' '3' '3'
4 '4' '$' '$' '$' '4' '4'
5 '5' '%' '%' '%' '5' '5'
6 '6' '^' '^' '^' '6' '6'
7 '7' '&' '&' '&' '7' '7'
8 '8' '*' '*' '*' '8' '8'
9 '9' '(' '(' '(' '9' '9'
GRAVE '`' '~' '`' '~' '`' '`'
MINUS '-' '_' '-' '_' '-' '-'
EQUALS '=' '+' '=' '+' '=' '='
LEFT_BRACKET '[' '{' '[' '{' '[' '['
RIGHT_BRACKET ']' '}' ']' '}' ']' ']'
BACKSLASH '\' '|' '\' '|' '\' '\'
SEMICOLON ';' ':' ';' ':' ';' ';'
APOSTROPHE ''' '"' ''' '"' ''' '''
STAR '*' '*' '*' '*' '*' '*'
POUND '#' '#' '#' '#' '#' '#'
PLUS '+' '+' '+' '+' '+' '+'
</pre>
<a name="androidKeymapKeyCharMapResourceBinaryFileFormat"></a><h4>Resource Binary File Format</h4>
<p>The file snippet above gets converted to the following by the <code>makekcharmap</code> tool as part of the build process. You can <code>mmap</code> this file in and share the approximately 4k of memory that it uses between processes to minimize load time.</p>
<table>
<tbody><tr>
<th scope="col">Offset</th>
<th scope="col">Size (bytes)</th>
<th scope="col">Description</th>
</tr>
<tr>
<td>0x00-0x0b</td>
<td></td>
<td>The ascii value "keycharmap1" including the null character</td>
</tr>
<tr>
<td>0x0c-0x0f</td>
<td></td>
<td>padding</td>
</tr>
<tr>
<td>0x10-0x13</td>
<td></td>
<td>The number of entries in the modifiers table (COLS)</td>
</tr>
<tr>
<td>0x14-0x17</td>
<td></td>
<td>The number of entries in the characters table (ROWS)</td>
</tr>
<tr>
<td>0x18-0x1f</td>
<td></td>
<td>padding</td>
</tr>
<tr>
<td></td>
<td>4*COLS</td>
<td>Modifiers table. The modifier mask values that each of the
columns in the characters table correspond to.</td>
</tr>
<tr>
<td></td>
<td></td>
<td>padding to the next 16 byte boundary</td>
</tr>
<tr>
<td></td>
<td>4*COLS*ROWS</td>
<td>Characters table. The modifier mask values that each of the
columns correspond to.</td>
</tr>
</tbody></table>
<a name="androidKeymapDriverTemplate"></a><h3>Implementing Your Own Driver (Driver Template)</h3>
<p>The following file, <code>pguide_events.c</code>, illustrates how to implement an Android keymap driver.</p>
<pre class="prettyprint">
/*
* pguide_events.c
*
* ANDROID PORTING GUIDE: INPUT EVENTS DRIVER TEMPLATE
*
* This template is designed to an example of the functionality
* necessary for Android to recieve input events. The PGUIDE_EVENT
* macros are meant as pointers indicating where to implement the
* hardware specific code necessary for the new device. The existence
* of the macros is not meant to trivialize the work required, just as
* an indication of where the work needs to be done.
*
* Copyright 2007, Google Inc.
* Based on goldfish-events.c
*
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/interrupt.h>
#include <linux/types.h>
#include <linux/input.h>
#include <linux/kernel.h>
#include <linux/platform_device.h>
#include <asm/irq.h>
#include <asm/io.h>
#define PGUIDE_EVENTS_INTERRUPT do{} while(0)
#define PGUIDE_EVENTS_PROBE do{} while(0)
struct event_dev {
struct input_dev *input;
int irq;
};
static irqreturn_t pguide_events_interrupt(int irq, void *dev_id)
{
struct event_dev *edev = dev_id;
unsigned type=0, code=0, value=0;
/* Set up type, code, and value per input.h
*/
PGUIDE_EVENTS_INTERRUPT;
input_event(edev->input, type, code, value);
return IRQ_HANDLED;
}
static int pguide_events_probe(struct platform_device *pdev)
{
struct input_dev *input_dev;
struct event_dev *edev;
printk("*** pguide events probe ***\n");
edev = kzalloc(sizeof(struct event_dev), GFP_KERNEL);
input_dev = input_allocate_device();
/* Setup edev->irq and do any hardware init */
PGUIDE_EVENTS_PROBE;
if(request_irq(edev->irq, pguide_events_interrupt, 0,
"pguide_events", edev) < 0) {
goto fail;
}
/* indicate that we generate key events */
set_bit(EV_KEY, input_dev->evbit);
set_bit(EV_REL, input_dev->evbit);
set_bit(EV_ABS, input_dev->evbit);
/* indicate that we generate *any* key event */
bitmap_fill(input_dev->keybit, KEY_MAX);
bitmap_fill(input_dev->relbit, REL_MAX);
bitmap_fill(input_dev->absbit, ABS_MAX);
platform_set_drvdata(pdev, edev);
input_dev->name = "pguide_events";
input_dev->private = edev;
input_dev->cdev.dev = &pdev->dev;
input_register_device(input_dev);
return 0;
fail:
kfree(edev);
input_free_device(input_dev);
return -EINVAL;
}
static struct platform_driver pguide_events_driver = {
.probe = pguide_events_probe,
.driver = {
.name = "pguide_events",
},
};
static int __devinit pguide_events_init(void)
{
return platform_driver_register(&pguide_events_driver);
}
static void __exit pguide_events_exit(void)
{
}
module_init(pguide_events_init);
module_exit(pguide_events_exit);
MODULE_DESCRIPTION("Pguide Event Device");
MODULE_LICENSE("GPL");
</pre>
<a name="androidKeymapKeyCharMapSampleImplementation"></a><h3>Sample Implementation</h3>
<p>Assume the following for the setup of a new keypad device:</p>
<pre class="prettify">
android.keylayout.partnerxx_keypad = /system/usr/keylayout/partnerxx_keypad.kl
android.keychar.partnerxx_keypad = /system/usr/keychars/partnerxx.kcm
</pre>
<p>The following example log file indicates that you have correctly registered the new keypad:</p>
<pre class="prettify">
I/EventHub( 1548): New device: path=/dev/input/event0 name=partnerxx_keypad id=0x10000 (of 0x1) index=1 fd=30
I/EventHub( 1548): new keyboard input device added, name = partnerxx_keypad
D/WindowManager( 1548): Starting input thread.
D/WindowManager( 1548): Startup complete!
I/EventHub( 1548): New keyboard: name=partnerxx_keypad
keymap=partnerxx_keypad.kl
keymapPath=/system/usr/keychars/partnerxx_keypad.kcm.bin
I/ServiceManager( 1535): ServiceManager: addService(window, 0x13610)
I/EventHub( 1548): Reporting device opened: id=0x10000, name=/dev/input/event0
I/KeyInputQueue( 1548): Device added: id=0x10000, name=partnerxx_keypad, classes=1
I/KeyInputQueue( 1548): Keymap: partnerxx_keypad.kl
</pre>
<p>The snippet above contains artificial line breaks to maintain a print-friendly document.</p>