[Linux device driver] Keypad interrupt latency 문제 해결 방법

static irqreturn_t unitron_interrupt(int irq, void *dev_id)
{
	struct unitron_data *data = dev_id;
	struct i2c_client *client = data->client;
	struct input_dev *input = data->input;
	int i;
	u8 key_low, key_high;
	u16 rawkey, keyval, mask = 0x01;
	u32 led		=	KEYPAD_LED;
 
	/* Read which key changed */
	rawkey = unitron_read(client, TC_MON_HIGH_REG);
	key_low = (rawkey>>8)&0xff;
	key_high = (rawkey)&0xff;
	rawkey = (key_high<<8)|(key_low);
 
	if(rawkey == 0x00){
		rawkey = data->last_keys;
		for (i = 0; i < ARRAY_SIZE(unitron_key2code); i++) {
			keyval = rawkey & mask;
			keyval >>= i;
			if (keyval){
				input_report_key(input, data->keycodes[i], 0);
			}
			mask <<= 1;
		}
	}
	else {
		for (i = 0; i < ARRAY_SIZE(unitron_key2code); i++) {
			keyval = rawkey & mask;
			keyval >>= i;
			if (keyval){
				input_report_key(input, data->keycodes[i], 1);
			}
			mask <<= 1;
		}
	}
	input_sync(input);
 
	data->last_keys = rawkey;
	return IRQ_HANDLED;
}