struct gpio_pin *dc_gpio_pin_by_attr_name(const char *name) {
	struct gpio_pin *pin;
	char *pin_attr_name;

	if (!strcmp(name, "led1")) {
		pin_attr_name = "dc-gpio1";
	} else if (!strcmp(name, "led2")) {
		pin_attr_name = "dc-gpio2";
	} else if (!strcmp(name, "dout-enable")) {
		pin_attr_name = "dc-gpio3";
	} else {
		log_error("accessory card attribute %s not available", name);
		return NULL;
	}

	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_dc_gpio_pin(struct device *dev,
			struct device_attribute *attr,
			char *buf)
{
	int value;
	struct gpio_pin *pin = dc_gpio_pin_by_attr_name(attr->attr.name);

	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_dc_gpio_pin(struct device *dev,
		struct device_attribute *attr, const char *buf, size_t count)
{
	int value;
	struct gpio_pin *pin = dc_gpio_pin_by_attr_name(attr->attr.name);

	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;
}

static ssize_t mts_attr_show_dc_din(struct device *dev, struct device_attribute *attr, char *buf)
{
	int tmp;
	u8 bit;
	u8 byte;

	if (!spi_dc_din_dev) {
		log_error("dc din device not present");
		return -ENODEV;
	}

	if (!strcmp(attr->attr.name, "din0")) {
		bit = BIT(0);
	} else if (!strcmp(attr->attr.name, "din1")) {
		bit = BIT(1);
	} else if (!strcmp(attr->attr.name, "din2")) {
		bit = BIT(2);
	} else if (!strcmp(attr->attr.name, "din3")) {
		bit = BIT(3);
	} else {
		log_error("dc din attr does not exist");
		return -ENOENT;
	}

	tmp = spi_readn(spi_dc_din_dev, &byte, 1);
	if (tmp) {
		log_error("spi_read failed %d", tmp);
		return tmp;
	}

	tmp = byte & bit ? 1 : 0;

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

static ssize_t mts_attr_store_dc_dout(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
{
	int value;
	u8 bit;

	if (!spi_dc_dout_dev) {
		log_error("dc dout device not present");
		return -ENODEV;
	}

	if (!strcmp(attr->attr.name, "dout0")) {
		bit = BIT(0);
	} else if (!strcmp(attr->attr.name, "dout1")) {
		bit = BIT(1);
	} else if (!strcmp(attr->attr.name, "dout2")) {
		bit = BIT(2);
	} else if (!strcmp(attr->attr.name, "dout3")) {
		bit = BIT(3);
	} else {
		log_error("dc dout attr does not exist");
		return -ENOENT;
	}

	if (sscanf(buf, "%i", &value) != 1) {
		log_error("dc dout attr invalid argument");
		return -EINVAL;
	}

	mutex_lock(&spi_dc_dout_mutex);

	if (value) {
		spi_dc_dout_value &= ~bit;
	} else {
		spi_dc_dout_value |= bit;
	}

	spi_writen(spi_dc_dout_dev, &spi_dc_dout_value, 1);

	mutex_unlock(&spi_dc_dout_mutex);

	return count;
}

static ssize_t mts_attr_show_dc_dout(struct device *dev, struct device_attribute *attr, char *buf)
{
	int value;
	u8 bit;

	if (!spi_dc_dout_dev) {
		log_error("dc dout device not present");
		return -ENODEV;
	}

	if (!strcmp(attr->attr.name, "dout0")) {
		bit = BIT(0);
	} else if (!strcmp(attr->attr.name, "dout1")) {
		bit = BIT(1);
	} else if (!strcmp(attr->attr.name, "dout2")) {
		bit = BIT(2);
	} else if (!strcmp(attr->attr.name, "dout3")) {
		bit = BIT(3);
	} else {
		log_error("dc dout attr does not exist");
		return -ENOENT;
	}

	mutex_lock(&spi_dc_dout_mutex);

	value = spi_dc_dout_value & bit ? 0 : 1;

	mutex_unlock(&spi_dc_dout_mutex);

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

static ssize_t mts_attr_show_dc_adc(struct device *dev, struct device_attribute *attr, char *buf)
{
	int tmp;
	int tx_data;
	int rx_data;
	int channel;
	int channel_mask = 0x0180;  /* 0b 0000 0001 1000 0000 */
	int manual_mode = 0x1840;   /* 0b 0001 1000 0100 0000 */
	uint8_t tx[2];
	uint8_t rx[2];

	if (!spi_dc_adc_dev) {
		log_error("dc adc device not present");
		return -ENODEV;
	}

	memset(tx, 0, sizeof(tx));
	memset(rx, 0, sizeof(rx));

	if (!strcmp(attr->attr.name, "adc0")) {
		channel = 0;
	} else if (!strcmp(attr->attr.name, "adc1")) {
		channel = 1;
	} else if (! strcmp(attr->attr.name, "adc2")) {
		channel = 2;
	} else {
		log_error("dc adc attr does not exist");
		return -ENOENT;
	}

	/* 1st transfer to set up (5V reference, channel to read from) */
	tx_data = manual_mode | ((channel << 7) & channel_mask);
	tx[0] = tx_data >> 8;
	tx[1] = tx_data & 0xFF;
	tmp = spi_writen(spi_dc_adc_dev, tx, 2);
	if (tmp) {
		log_error("spi_write failed %d", tmp);
		return tmp;
	}

	/* 2nd transfer to clock chip for ADC conversion
	 * this can be a throw-away read or an empty write,
	 * the ADC just needs the clock running so it can convert */
	tx[0] = 0;
	tx[1] = 0;
	tmp = spi_writen(spi_dc_adc_dev, tx, 2);
	if (tmp) {
		log_error("2nd spi_write failed %d", tmp);
		return tmp;
	}

	/* 3rd transfer to read data */
	tmp = spi_readn(spi_dc_adc_dev, rx, 2);
	if (tmp) {
		log_error("spi_read failed %d", tmp);
		return tmp;
	}
	rx_data = ((rx[0] & 0x0F) << 8) | (rx[1] & 0xFF);

	return sprintf(buf, "%lu\n", (unsigned long) rx_data);
}

/* MTDC-GPIOB */
static DEVICE_ATTR_RO_MTS(dev_attr_dc_din0, "din0", mts_attr_show_dc_din);
static DEVICE_ATTR_RO_MTS(dev_attr_dc_din1, "din1", mts_attr_show_dc_din);
static DEVICE_ATTR_RO_MTS(dev_attr_dc_din2, "din2", mts_attr_show_dc_din);
static DEVICE_ATTR_RO_MTS(dev_attr_dc_din3, "din3", mts_attr_show_dc_din);
static DEVICE_ATTR_MTS(dev_attr_dc_dout0, "dout0", mts_attr_show_dc_dout, mts_attr_store_dc_dout);
static DEVICE_ATTR_MTS(dev_attr_dc_dout1, "dout1", mts_attr_show_dc_dout, mts_attr_store_dc_dout);
static DEVICE_ATTR_MTS(dev_attr_dc_dout2, "dout2", mts_attr_show_dc_dout, mts_attr_store_dc_dout);
static DEVICE_ATTR_MTS(dev_attr_dc_dout3, "dout3", mts_attr_show_dc_dout, mts_attr_store_dc_dout);
static DEVICE_ATTR_RO_MTS(dev_attr_dc_adc0, "adc0", mts_attr_show_dc_adc);
static DEVICE_ATTR_RO_MTS(dev_attr_dc_adc1, "adc1", mts_attr_show_dc_adc);
static DEVICE_ATTR_RO_MTS(dev_attr_dc_adc2, "adc2", mts_attr_show_dc_adc);
static DEVICE_ATTR_MTS(dev_attr_dc_led1, "led1", mts_attr_show_dc_gpio_pin, mts_attr_store_dc_gpio_pin);
static DEVICE_ATTR_MTS(dev_attr_dc_led2, "led2", mts_attr_show_dc_gpio_pin, mts_attr_store_dc_gpio_pin);
static DEVICE_ATTR_MTS(dev_attr_dc_oe, "dout-enable", mts_attr_show_dc_gpio_pin, mts_attr_store_dc_gpio_pin);