Advantech RSB-4210 Evaluation Kit Manual de usuario descargar pdf (Pagina 102)

RSB-4210 User Manual 94

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.

This should be the way for GPM and X to get keyboard and 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

...

And so on up to event31.

3. Verifying if it works

Typing a couple keys on the keyboard should be enough to check that a USB key-

board 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/input/joystick.txt).

You can test the event devices with the 'evtest' utility available in the LinuxConsole

project CVS archive (see the URL below).

4. Event interface

Should you want to add event device support into any application (X, gpm, svgalib ...)

I <vojtech@ucw.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/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/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.

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