/dev/button:

read interface for button events:

1st byte: button:		2nd byte: 0x00 release / 0x80 pushed

0x80	flip
0x81	answer button on headset
0x82	headset plug
0x83	charger_500mA ?
0x84	usb plug event
0x85	charger_0 ?

The device is poll() able

The flip seems to be directly connected to a GPIO pin (GPIO_FLIP_PIN) that
generates interrupts

There are dedicated ioctl's for getting headset and flip status(!)