UM0851 datasheet(182/245 Pages) STMICROELECTRONICS

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Human interface device (HID) drivers

UM0851

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Doc ID 16604 Rev 2

static struct spear_kp_platform_data spear_kbd_data = {

.keymap

= spear_keymap,

.keymapsize

= ARRAY_SIZE(spear_keymap),

.rep

= 1,

};

●

.keymap :Pointer to the Keymap table

●

.keymapsize :Array size of the Keymap table (usually # = rows x cols)

●

.rep :Repeat key support ('1' if supported)

Below is the example for the Keymap table

static int spear_keymap[] = {

KEY(0, 0, KEY_ESC),

KEY(0, 1, KEY_1),

KEY(1, 3, KEY_3),

KEY(1, 4, KEY_4),

KEY(8, 8, KEY_EQUAL),

}

The keymap table is fully customizable and can support a keypad with a generic NxM matrix

(9x9 is the maximum matrix size). The format is like KEY(row , col, val).

7.2.4

Keypad usage

The keypad driver provides an event interface to the input layer. Evdev is the generic input

event interface. It passes the events generated in the kernel straight to the program, with

timestamps.

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

The device nodes are created in /dev/input directory with the major number 13 and minor

number 64. The device can be opened using the open() system call in both blocking and

non-blocking modes, and read using the select() system call on the /dev/input/eventX

devices, which will 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, REL_KEY for a key press or key 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.

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