static struct kobj_attribute* create_attribute(const char* _name, umode_t _mode) {
	char* attr_name;
	struct kobj_attribute* _attr;
	
	_attr = kzalloc(sizeof(struct kobj_attribute), GFP_KERNEL);
	if (! _attr) {
		log_error("kzalloc of attribute [%s] failed", _name);
		return NULL;
	}

	sysfs_attr_init(_attr);
	attr_name = kstrdup(_name, GFP_KERNEL);
	if (! attr_name) {
		log_error("GFP_KERNEL dup failed for attribute [%s]", _name);
		return NULL;
	}

	_attr->attr.name = attr_name;
	_attr->attr.mode = _mode;

	return _attr;
}

static int port_from_kobject(struct kobject *kobj) {
	int port;
	const char *name;

	name = kobj->name;
	if (! name) {
		log_error("kobject->name is NULL");
		return -1;
	}

	if (sscanf(name, "ap%d", &port) < 1) {
		log_error("failed to scan port from kobject->name [%s]", name);
		return -1;
	}

	if (port < 1 || port > NUM_AP) {
		log_error("port number %d is invalid", port);
		return -1;
	}

	return port;
}

static ssize_t ap_show_product_info(struct kobject *kobj, struct kobj_attribute *attr, char *buf) {
	ssize_t value;
	int port;
	int port_index;

	port = port_from_kobject(kobj);
	if (port < 1) {
		log_error("port_from_kobject returned %d", port);
		return -1;
	}
	port_index = port - 1;

	if (! strcmp(attr->attr.name, "vendor-id")) {
		value = snprintf(buf, 32, "%s\n", ap_eeprom[port_index].vendor_id);
	} else if (! strcmp(attr->attr.name, "product-id")) {
		value = snprintf(buf, 32, "%s\n", ap_eeprom[port_index].product_id);
	} else if (! strcmp(attr->attr.name, "device-id")) {
		value = snprintf(buf, 32, "%s\n", ap_eeprom[port_index].device_id);
	} else if (! strcmp(attr->attr.name, "hw-version")) {
		value = snprintf(buf, 32, "%s\n", ap_eeprom[port_index].hw_version);
	} else if (! strcmp(attr->attr.name, "mac-addr")) {
		value = sprintf(buf, "%02X:%02X:%02X:%02X:%02X:%02X\n",
			ap_eeprom[port_index].mac_addr[0],
			ap_eeprom[port_index].mac_addr[1],
			ap_eeprom[port_index].mac_addr[2],
			ap_eeprom[port_index].mac_addr[3],
			ap_eeprom[port_index].mac_addr[4],
			ap_eeprom[port_index].mac_addr[5]);
	} else if (! strcmp(attr->attr.name, "eui")) {
		value = sprintf(buf, "%02X:%02X:%02X:%02X:%02X:%02X:%02X:%02X\n",
			ap_eeprom[port_index].eui[0],
			ap_eeprom[port_index].eui[1],
			ap_eeprom[port_index].eui[2],
			ap_eeprom[port_index].eui[3],
			ap_eeprom[port_index].eui[4],
			ap_eeprom[port_index].eui[5],
			ap_eeprom[port_index].eui[6],
			ap_eeprom[port_index].eui[7]);
	} else {
		log_error("attribute [%s] not found", attr->attr.name);
		value = -1;
	}

	return value;
}

static bool ap_add_product_info_attributes(int port, int type, struct attribute** attrs, int* index) {
	char buf[32];
	struct kobj_attribute* kobj_attr;

	switch (type) {
		case MTAC_ETH_0_0:
			sprintf(buf, "mac-addr");
			kobj_attr = create_attribute(buf, MTS_ATTR_MODE_RO);
			if (! kobj_attr) {
				log_error("failed to create attribute [%s] in port %d", buf, port);
				return false;
			}
			kobj_attr->show = ap_show_product_info;
			attrs[(*index)++] = &kobj_attr->attr;
			break;

		case MTAC_GPIOB_0_0:
		case MTAC_MFSER_0_0:
			break;

		case MTAC_LORA_0_0:
		case MTAC_LORA_1_0:
		case MTAC_LORA_1_5:
			sprintf(buf, "eui");
			kobj_attr = create_attribute(buf, MTS_ATTR_MODE_RO);
			if (! kobj_attr) {
				log_error("failed to create attribute [%s] in port %d", buf, port);
				return false;
			}
			kobj_attr->show = ap_show_product_info;
			attrs[(*index)++] = &kobj_attr->attr;
			break;

		default:
			log_error("invalid accessory card type");
			return false;
	}

	sprintf(buf, "vendor-id");
	kobj_attr = create_attribute(buf, MTS_ATTR_MODE_RO);
	if (! kobj_attr) {
		log_error("failed to create attribute [%s] in port %d", buf, port);
		return false;
	}
	kobj_attr->show = ap_show_product_info;
	attrs[(*index)++] = &kobj_attr->attr;

	sprintf(buf, "product-id");
	kobj_attr = create_attribute(buf, MTS_ATTR_MODE_RO);
	if (! kobj_attr) {
		log_error("failed to create attribute [%s] in port %d", buf, port);
		return false;
	}
	kobj_attr->show = ap_show_product_info;
	attrs[(*index)++] = &kobj_attr->attr;

	sprintf(buf, "device-id");
	kobj_attr = create_attribute(buf, MTS_ATTR_MODE_RO);
	if (! kobj_attr) {
		log_error("failed to create attribute [%s] in port %d", buf, port);
		return false;
	}
	kobj_attr->show = ap_show_product_info;
	attrs[(*index)++] = &kobj_attr->attr;

	sprintf(buf, "hw-version");
	kobj_attr = create_attribute(buf, MTS_ATTR_MODE_RO);
	if (! kobj_attr) {
		log_error("failed to create attribute [%s] in port %d", buf, port);
		return false;
	}
	kobj_attr->show = ap_show_product_info;
	attrs[(*index)++] = &kobj_attr->attr;

	return true;
}

struct gpio_pin *ap_gpio_pin_by_attr_name(const char *name, int port) {
	struct gpio_pin *pin;
	char *pin_attr_name;
	int port_index = port - 1;

	pin_attr_name = port_info[port_index]->gpio_pin_name_by_attr_name(name, port);

	for (pin = gpio_pins; *pin->name; pin++) {
		if (!strcmp(pin->pin.label, pin_attr_name)) {
			return pin;
		}
	}

	log_error("pin with attr name [%s] not found", name);
	return NULL;
}

static ssize_t mts_attr_show_ap_gpio_pin(struct kobject *kobj,
			struct kobj_attribute *attr,
			char *buf)
{
	int value;
	int port;
	struct gpio_pin *pin;
	   
	port = port_from_kobject(kobj);
	if (port < 1) {
		log_error("port_from_kobject returned %d", port);
		return -EINVAL;
	}

	pin	= ap_gpio_pin_by_attr_name(attr->attr.name, port);
	if (!pin) {
		return -ENODEV;
	}

	mutex_lock(&mts_io_mutex);

	value = gpio_get_value(pin->pin.gpio);

	mutex_unlock(&mts_io_mutex);

	if (value < 0) {
		return value;
	}

	if (pin->active_low) {
		value = !value;
	}

	return sprintf(buf, "%d\n", value);
}

static ssize_t mts_attr_store_ap_gpio_pin(struct kobject *kobj,
		struct kobj_attribute *attr, const char *buf, size_t count)
{
	int value;
	int port;
	struct gpio_pin *pin;

	port = port_from_kobject(kobj);
	if (port < 1) {
		log_error("port_from_kobject returned %d", port);
		return -EINVAL;
	}
	   
	pin	= ap_gpio_pin_by_attr_name(attr->attr.name, port);
	if (!pin) {
		return -ENODEV;
	}

	if (sscanf(buf, "%i", &value) != 1) {
		return -EINVAL;
	}

	if (pin->active_low) {
		value = !value;
	}

	mutex_lock(&mts_io_mutex);

	gpio_set_value(pin->pin.gpio, value);

	mutex_unlock(&mts_io_mutex);

	return count;
}