buzzer_attr.c

static ssize_t attr_store(struct device *dev,
		struct device_attribute *attr,
		const char *buf, size_t count)
{

	printk("[%s][%d]\n", __func__, __LINE__);
	buzzer_trigger = simple_strtoul(buf, NULL, 10);
	gpio_set_value(BUZZER, buzzer_trigger);
	return count;
}

static ssize_t attr_show(struct device *dev,
		struct device_attribute *attr,
		char *buf)
{
    int val = 0;
    printk("[%s][%d]\n", __func__, __LINE__);
    val = sprintf(buf, "%d\n", buzzer_trigger);
    return val;
}