mts-io: clean up accessory card support

	use custom kernel config option MTS_NUM_ACCESSORY_PORTS to find out how many slots exist
	(mostly) dynamically handle any number of accessory cards
	streamline code to make it easier to add accessory cards in the future

8 files changed, 532 insertions, 847 deletions

diff --git a/io-module/Makefile b/io-module/Makefile
index f95a55e..5d036f4 100644
--- a/io-module/Makefile
+++ b/io-module/Makefile
@@ -1,5 +1,4 @@
 obj-m := mts_io.o
-CFLAGS_mts_io.o := ${DAUGHTER_CARD}
 
 clean:
 	rm -f *.ko *.o
diff --git a/io-module/mtac.c b/io-module/mtac.c
new file mode 100644
index 0000000..b9a2520
--- /dev/null
+++ b/io-module/mtac.c
@@ -0,0 +1,22 @@
+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;
+}
diff --git a/io-module/mtac_gpiob.c b/io-module/mtac_gpiob.c
index 5a592b7..728634d 100644
--- a/io-module/mtac_gpiob.c
+++ b/io-module/mtac_gpiob.c
@@ -1,22 +1,130 @@
+struct spi_device *gpiob_spi[NUM_AP][3];
+struct spi_driver gpiob_spi_drivers[NUM_AP][3];
+
+static u8 spi_ap_dout_value;
+static DEFINE_MUTEX(spi_ap_dout_mutex);
+static unsigned int ap_dout_max_speed_hz = 1 * 1000 * 1000;
+module_param(ap_dout_max_speed_hz, uint, S_IRUGO);
+MODULE_PARM_DESC(
+	ap_dout_max_speed_hz,
+	"Maximum clock rate to be used with this device (default: 1 MHz)"
+);
+
+static unsigned int ap_din_max_speed_hz = 1 * 1000 * 1000;
+module_param(ap_din_max_speed_hz, uint, S_IRUGO);
+MODULE_PARM_DESC(
+	ap_din_max_speed_hz,
+	"Maximum clock rate to be used with this device (default: 1 MHz)"
+);
+
+static unsigned int ap_adc_max_speed_hz = 20 * 1000 * 1000;
+module_param(ap_adc_max_speed_hz, uint, S_IRUGO);
+MODULE_PARM_DESC(
+	ap_adc_max_speed_hz,
+	"Maximum clock rate to be used with this device (default: 20 MHz)"
+);
+
+static bool gpiob_get_dev_info_from_modalias(const char* modalias, int* port, char* buf) {
+	sscanf(modalias, "mts-io-ap%d-%s", port, buf);
+
+	return true;
+}
+
+static int mts_spi_ap_probe(struct spi_device *spi)
+{
+	int tmp;
+	int port;
+	int port_index;
+	char buf[16];
+	enum spi_devices dev;
+
+	gpiob_get_dev_info_from_modalias(spi->modalias, &port, buf);
+	port_index = port - 1;
+	if (port < 1 || port > NUM_AP) {
+		log_error("port [%d] is invalid", port);
+		return -ENODEV;
+	}
+
+	if (strstr(buf, "dout")) {
+		dev = dout;
+		spi->max_speed_hz = ap_dout_max_speed_hz;
+		spi->mode = 0;
+	} else if (strstr(buf, "din")) {
+		dev = din;
+		spi->max_speed_hz = ap_din_max_speed_hz;
+		spi->mode = SPI_CPOL;
+	} else if (strstr(buf, "adc")) {
+		dev = adc;
+		spi->max_speed_hz = ap_adc_max_speed_hz;
+		spi->mode = 0;
+	} else {
+		log_error("unknown gpiob spi device type [%s]", buf);
+		return -ENODEV;
+	}
+
+	gpiob_spi[port_index][dev] = spi;
+
+	tmp = spi_setup(gpiob_spi[port_index][dev]);
+	if (tmp < 0) {
+		log_error("spi_setup ap %d %s failed", port, buf);
+		return tmp;
+	}
+
+	if (dev == dout) {
+		spi_ap_dout_value = 0x00;
+		spi_writen(gpiob_spi[port_index][dev], &spi_ap_dout_value, 1);
+	}
+
+	return 0;
+}
+
+static int mts_spi_ap_remove(struct spi_device *spi)
+{
+	int port;
+	int port_index;
+	char buf[16];
+
+	gpiob_get_dev_info_from_modalias(spi->modalias, &port, buf);
+	port_index = port - 1;
+	if (port < 1 || port > NUM_AP) {
+		log_error("port [%d] is invalid", port);
+		return -ENODEV;
+	}
+
+	if (strstr(buf, "dout")) {
+		gpiob_spi[port_index][dout] = NULL;
+	} else if (strstr(buf, "din")) {
+		gpiob_spi[port_index][din] = NULL;
+	} else if (strstr(buf, "adc")) {
+		gpiob_spi[port_index][adc] = NULL;
+	} else {
+		log_error("unknown gpiob spi device type [%s]", buf);
+		return -ENODEV;
+	}
+
+	return 0;
+}
+
+// Is there a way to make this dynamic as well?
 struct gpio_pin *ap_gpio_pin_by_attr_name(const char *name) {
 	struct gpio_pin *pin;
 	char *pin_attr_name;
 
-	if (!strcmp(name, "ap1-led1")) {
+	if (!strcmp(name, "ap-led1:1")) {
 		pin_attr_name = "ap1-gpio3";
-	} else if (!strcmp(name, "ap1-led2")) {
+	} else if (!strcmp(name, "ap-led2:1")) {
 		pin_attr_name = "ap1-gpio4";
-	} else if (!strcmp(name, "ap1-dout-enable")) {
+	} else if (!strcmp(name, "ap-dout-enable:1")) {
 		pin_attr_name = "ap1-gpio1";
-	} else if (!strcmp(name, "ap1-reset")) {
+	} else if (!strcmp(name, "ap-reset:1")) {
 		pin_attr_name = "ap1-reset";
-	} else if (!strcmp(name, "ap2-led1")) {
+	} else if (!strcmp(name, "ap-led1:2")) {
 		pin_attr_name = "ap2-gpio3";
-	} else if (!strcmp(name, "ap2-led2")) {
+	} else if (!strcmp(name, "ap-led2:2")) {
 		pin_attr_name = "ap2-gpio4";
-	} else if (!strcmp(name, "ap2-dout-enable")) {
+	} else if (!strcmp(name, "ap-dout-enable:2")) {
 		pin_attr_name = "ap2-gpio1";
-	} else if (!strcmp(name, "ap2-reset")) {
+	} else if (!strcmp(name, "ap-reset:2")) {
 		pin_attr_name = "ap2-reset";
 	} else {
 		log_error("accessory card attribute %s not available", name);
@@ -35,8 +143,8 @@ struct gpio_pin *ap_gpio_pin_by_attr_name(const char *name) {
 }
 
 
-static ssize_t mts_attr_show_ap_gpio_pin(struct device *dev,
-			struct device_attribute *attr,
+static ssize_t mts_attr_show_ap_gpio_pin(struct kobject *kobj,
+			struct kobj_attribute *attr,
 			char *buf)
 {
 	int value;
@@ -63,8 +171,8 @@ static ssize_t mts_attr_show_ap_gpio_pin(struct device *dev,
 	return sprintf(buf, "%d\n", value);
 }
 
-static ssize_t mts_attr_store_ap_gpio_pin(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t count)
+static ssize_t mts_attr_store_ap_gpio_pin(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
 {
 	int value;
 	struct gpio_pin *pin = ap_gpio_pin_by_attr_name(attr->attr.name);
@@ -90,46 +198,29 @@ static ssize_t mts_attr_store_ap_gpio_pin(struct device *dev,
 	return count;
 }
 
-static ssize_t mts_attr_show_ap_din(struct device *dev, struct device_attribute *attr, char *buf)
+static ssize_t mts_attr_show_ap_din(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
 	int tmp;
+	int channel;
+	int port;
+	int port_index;
 	u8 bit;
 	u8 byte;
-	struct spi_device* spi_dev;
 
-	if (strstr(attr->attr.name, ":0")) {
-		if (!spi_ap1_din_dev) {
-			log_error("accessory card 1 din device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap1_din_dev;
-	} else if (strstr(attr->attr.name, ":1")) {
-		if (!spi_ap2_din_dev) {
-			log_error("accessory card 2 din device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap2_din_dev;
-	} else {
-		log_error("unknown din device %s", attr->attr.name);
-		return -ENODEV;
+	sscanf(attr->attr.name, "din%d:%d", &channel, &port);
+	port_index = port - 1;
+	if (channel < 0 || channel > 3) {
+		log_error("channel [%d] is invalid", channel);
+		return -ENOENT;
 	}
-
-	if (strstr(attr->attr.name, "din0")) {
-		bit = BIT(0);
-	} else if (strstr(attr->attr.name, "din1")) {
-		bit = BIT(1);
-	} else if (strstr(attr->attr.name, "din2")) {
-		bit = BIT(2);
-	} else if (strstr(attr->attr.name, "din3")) {
-		bit = BIT(3);
-	} else {
-		log_error("accessory card din attr does not exist");
+	if (port < 1 || port > NUM_AP) {
+		log_error("port [%d] is invalid", port);
 		return -ENOENT;
 	}
 
-	tmp = spi_readn(spi_dev, &byte, 1);
+	bit = BIT(channel);
+
+	tmp = spi_readn(gpiob_spi[port_index][din], &byte, 1);
 	if (tmp) {
 		log_error("spi_read failed %d", tmp);
 		return tmp;
@@ -140,46 +231,29 @@ static ssize_t mts_attr_show_ap_din(struct device *dev, struct device_attribute
 	return sprintf(buf, "%d\n", tmp);
 }
 
-static ssize_t mts_attr_store_ap_dout(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+static ssize_t mts_attr_store_ap_dout(struct kobject *kobj, struct kobj_attribute *attr, const char *buf, size_t count)
 {
 	int value;
+	int channel;
+	int port;
+	int port_index;
 	u8 bit;
-	struct spi_device* spi_dev;
-
-	if (strstr(attr->attr.name, ":0")) {
-		if (!spi_ap1_dout_dev) {
-			log_error("accessory card 1 dout device not present");
-			return -ENODEV;
-		}
 
-		spi_dev = spi_ap1_dout_dev;
-	} else if (strstr(attr->attr.name, ":1")) {
-		if (!spi_ap2_dout_dev) {
-			log_error("accessory card 2 dout device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap2_dout_dev;
-	} else {
-		log_error("unknown dout device %s", attr->attr.name);
-		return -ENODEV;
+	sscanf(attr->attr.name, "dout%d:%d", &channel, &port);
+	port_index = port - 1;
+	if (channel < 0 || channel > 3) {
+		log_error("channel [%d] is invalid", channel);
+		return -ENOENT;
 	}
-
-	if (strstr(attr->attr.name, "dout0")) {
-		bit = BIT(0);
-	} else if (strstr(attr->attr.name, "dout1")) {
-		bit = BIT(1);
-	} else if (strstr(attr->attr.name, "dout2")) {
-		bit = BIT(2);
-	} else if (strstr(attr->attr.name, "dout3")) {
-		bit = BIT(3);
-	} else {
-		log_error("accessory card dout attr does not exist");
+	if (port < 1 || port > NUM_AP) {
+		log_error("port [%d] is invalid", port);
 		return -ENOENT;
 	}
 
+	bit = BIT(channel);
+
 	if (sscanf(buf, "%i", &value) != 1) {
-		log_error("accessory card dout attr invalid argument");
+		log_error("accessory card dout attr invalid argument [%d]", value);
 		return -EINVAL;
 	}
 
@@ -191,51 +265,32 @@ static ssize_t mts_attr_store_ap_dout(struct device *dev, struct device_attribut
 		spi_ap_dout_value |= bit;
 	}
 
-	spi_writen(spi_dev, &spi_ap_dout_value, 1);
+	spi_writen(gpiob_spi[port_index][dout], &spi_ap_dout_value, 1);
 
 	mutex_unlock(&spi_ap_dout_mutex);
 
 	return count;
 }
 
-static ssize_t mts_attr_show_ap_dout(struct device *dev, struct device_attribute *attr, char *buf)
+static ssize_t mts_attr_show_ap_dout(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
 	int value;
+	int channel;
+	int port;
 	u8 bit;
-	struct spi_device* spi_dev;
 
-	if (strstr(attr->attr.name, ":0")) {
-		if (!spi_ap1_dout_dev) {
-			log_error("accessory card 1 dout device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap1_dout_dev;
-	} else if (strstr(attr->attr.name, ":1")) {
-		if (!spi_ap2_dout_dev) {
-			log_error("accessory card 2 dout device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap2_dout_dev;
-	} else {
-		log_error("unknown dout device %s", attr->attr.name);
-		return -ENODEV;
+	sscanf(attr->attr.name, "dout%d:%d", &channel, &port);
+	if (channel < 0 || channel > 3) {
+		log_error("channel [%d] is invalid", channel);
+		return -ENOENT;
 	}
-
-	if (strstr(attr->attr.name, "dout0")) {
-		bit = BIT(0);
-	} else if (strstr(attr->attr.name, "dout1")) {
-		bit = BIT(1);
-	} else if (strstr(attr->attr.name, "dout2")) {
-		bit = BIT(2);
-	} else if (strstr(attr->attr.name, "dout3")) {
-		bit = BIT(3);
-	} else {
-		log_error("accessory card dout attr does not exist");
+	if (port < 1 || port > NUM_AP) {
+		log_error("port [%d] is invalid", port);
 		return -ENOENT;
 	}
 
+	bit = BIT(channel);
+
 	mutex_lock(&spi_ap_dout_mutex);
 
 	value = spi_ap_dout_value & bit ? 0 : 1;
@@ -245,48 +300,30 @@ static ssize_t mts_attr_show_ap_dout(struct device *dev, struct device_attribute
 	return sprintf(buf, "%d\n", value);
 }
 
-static ssize_t mts_attr_show_ap_adc(struct device *dev, struct device_attribute *attr, char *buf)
+static ssize_t mts_attr_show_ap_adc(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
 	int tmp;
 	int tx_data;
 	int rx_data;
 	int channel;
+	int port;
+	int port_index;
 	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];
-	struct spi_device* spi_dev;
 
 	memset(tx, 0, sizeof(tx));
 	memset(rx, 0, sizeof(rx));
 
-	if (strstr(attr->attr.name, ":0")) {
-		if (!spi_ap1_adc_dev) {
-			log_error("accessory card 1 adc device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap1_adc_dev;
-	} else if (strstr(attr->attr.name, ":1")) {
-		if (!spi_ap2_adc_dev) {
-			log_error("accessory card 2 adc device not present");
-			return -ENODEV;
-		}
-
-		spi_dev = spi_ap2_adc_dev;
-	} else {
-		log_error("unknown adc device %s", attr->attr.name);
-		return -ENODEV;
+	sscanf(attr->attr.name, "adc%d:%d", &channel, &port);
+	port_index = port - 1;
+	if (channel < 0 || channel > 2) {
+		log_error("channel [%d] is invalid", channel);
+		return -ENOENT;
 	}
-
-	if (strstr(attr->attr.name, "adc0")) {
-		channel = 0;
-	} else if (strstr(attr->attr.name, "adc1")) {
-		channel = 1;
-	} else if (strstr(attr->attr.name, "adc2")) {
-		channel = 2;
-	} else {
-		log_error("accessory card adc attr does not exist");
+	if (port < 1 || port > NUM_AP) {
+		log_error("port [%d] is invalid", port);
 		return -ENOENT;
 	}
 
@@ -294,7 +331,7 @@ static ssize_t mts_attr_show_ap_adc(struct device *dev, struct device_attribute
 	tx_data = manual_mode | ((channel << 7) & channel_mask);
 	tx[0] = tx_data >> 8;
 	tx[1] = tx_data & 0xFF;
-	tmp = spi_writen(spi_dev, tx, 2);
+	tmp = spi_writen(gpiob_spi[port_index][adc], tx, 2);
 	if (tmp) {
 		log_error("spi_write failed %d", tmp);
 		return tmp;
@@ -305,14 +342,14 @@ static ssize_t mts_attr_show_ap_adc(struct device *dev, struct device_attribute
 	 * the ADC just needs the clock running so it can convert */
 	tx[0] = 0;
 	tx[1] = 0;
-	tmp = spi_writen(spi_dev, tx, 2);
+	tmp = spi_writen(gpiob_spi[port_index][adc], tx, 2);
 	if (tmp) {
 		log_error("2nd spi_write failed %d", tmp);
 		return tmp;
 	}
 
 	/* 3rd transfer to read data */
-	tmp = spi_readn(spi_dev, rx, 2);
+	tmp = spi_readn(gpiob_spi[port_index][adc], rx, 2);
 	if (tmp) {
 		log_error("spi_read failed %d", tmp);
 		return tmp;
@@ -322,88 +359,165 @@ static ssize_t mts_attr_show_ap_adc(struct device *dev, struct device_attribute
 	return sprintf(buf, "%lu\n", (unsigned long) rx_data);
 }
 
-/* accessory port 1 gpiob attributes */
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_din0, "din0:0", mts_attr_show_ap_din);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_din1, "din1:0", mts_attr_show_ap_din);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_din2, "din2:0", mts_attr_show_ap_din);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_din3, "din3:0", mts_attr_show_ap_din);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_dout0, "dout0:0", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_dout1, "dout1:0", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_dout2, "dout2:0", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_dout3, "dout3:0", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_adc0, "adc0:0", mts_attr_show_ap_adc);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_adc1, "adc1:0", mts_attr_show_ap_adc);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap1_gpio_adc2, "adc2:0", mts_attr_show_ap_adc);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_led1, "ap1-led1", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_led2, "ap1-led2", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap1_gpio_oe, "ap1-dout-enable", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap1_reset, "ap1-reset", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-
-static int ap1_gpio_attributes_size = 15;		// not including NULL at end
-
-static struct attribute *ap1_gpio_attributes[] = {
-	&dev_attr_ap1_reset.attr,
-
-	&dev_attr_ap1_gpio_oe.attr,			// gpio1
-	&dev_attr_ap1_gpio_led1.attr,		// gpio3
-	&dev_attr_ap1_gpio_led2.attr,		// gpio4
-
-	&dev_attr_ap1_gpio_din0.attr,
-	&dev_attr_ap1_gpio_din1.attr,
-	&dev_attr_ap1_gpio_din2.attr,
-	&dev_attr_ap1_gpio_din3.attr,
-
-	&dev_attr_ap1_gpio_dout0.attr,
-	&dev_attr_ap1_gpio_dout1.attr,
-	&dev_attr_ap1_gpio_dout2.attr,
-	&dev_attr_ap1_gpio_dout3.attr,
-
-	&dev_attr_ap1_gpio_adc0.attr,
-	&dev_attr_ap1_gpio_adc1.attr,
-	&dev_attr_ap1_gpio_adc2.attr,
-
-	NULL,
-};
+static bool gpiob_spi_driver_setup(struct spi_driver *driver, const char *driver_name) {
+	char* name = kstrdup(driver_name, GFP_KERNEL);
+	if (! name) {
+		log_error("GFP_KERNEL dup failed for driver [%s]", driver_name);
+		return false;
+	}
+	driver->driver.name = name;
+	driver->driver.bus = &spi_bus_type;
+	driver->driver.owner = THIS_MODULE;
+	driver->probe = mts_spi_ap_probe;
+	driver->remove = mts_spi_ap_remove;
+
+	return true;
+}
+
+// 4 digital inputs
+// 4 digital outputs
+// 3 analog to digital
+// 2 LEDs
+// 1 digital out enable
+// 1 reset
+static int ap_gpiob_attrs_size = 15;
+
+static bool gpiob_setup(enum ap port) {
+	int i;
+	int port_index = port - 1;
+	struct kobj_attribute *attr;
+	char buf[32];
+
+	log_info("loading GPIOB accessory card in port %d", port);
+
+	if (device_attrs_size + ap_gpiob_attrs_size >= device_attrs_max_size) {
+		log_error("can't load GPIOB accessory card in port %d - not enough room for attributes", port);
+		return false;
+	}
+
+	// add digital inputs
+	for (i = 0; i < 4; i++) {
+		sprintf(buf, "din%d:%d", i, port);
+		attr = create_attribute(buf, MTS_ATTR_MODE_RO);
+		if (! attr) {
+			log_error("failed to create attribute[%s]", buf);
+			return false;
+		}
+		attr->show = mts_attr_show_ap_din;
+		device_attrs[device_attrs_size++] = &attr->attr;
+	}
+
+	// add digital outputs
+	for (i = 0; i < 4; i++) {
+		sprintf(buf, "dout%d:%d", i, port);
+		attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+		if (! attr) {
+			log_error("failed to create attribute[%s]", buf);
+			return false;
+		}
+		attr->show = mts_attr_show_ap_dout;
+		attr->store = mts_attr_store_ap_dout;
+		device_attrs[device_attrs_size++] = &attr->attr;
+	}
+
+	// add analog to digital
+	for (i = 0; i < 3; i++) {
+		sprintf(buf, "adc%d:%d", i, port);
+		attr = create_attribute(buf, MTS_ATTR_MODE_RO);
+		if (! attr) {
+			log_error("failed to create attribute[%s]", buf);
+			return false;
+		}
+		attr->show = mts_attr_show_ap_adc;
+		device_attrs[device_attrs_size++] = &attr->attr;
+	}
+
+	// add LEDs
+	for (i = 1; i <= 2; i++) {
+		sprintf(buf, "ap-led%d:%d", i, port);
+		attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+		if (! attr) {
+			log_error("failed to create attribute[%s]", buf);
+			return false;
+		}
+		attr->show = mts_attr_show_ap_gpio_pin;
+		attr->store = mts_attr_store_ap_gpio_pin;
+		device_attrs[device_attrs_size++] = &attr->attr;
+	}
+
+	// misc attributes
+	sprintf(buf, "ap-dout-enable:%d", port);
+	attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+	if (! attr) {
+		log_error("failed to create attribute[%s]", buf);
+		return false;
+	}
+	attr->show = mts_attr_show_ap_gpio_pin;
+	attr->store = mts_attr_store_ap_gpio_pin;
+	device_attrs[device_attrs_size++] = &attr->attr;
+
+	sprintf(buf, "ap-reset:%d", port);
+	attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+	if (! attr) {
+		log_error("failed to create attribute[%s]", buf);
+		return false;
+	}
+	attr->show = mts_attr_show_ap_gpio_pin;
+	attr->store = mts_attr_store_ap_gpio_pin;
+	device_attrs[device_attrs_size++] = &attr->attr;
+
+	// setup and register drivers
+	log_debug("registering accessory card %d dout driver", port);
+	sprintf(buf, "mts-io-ap%d-dout", port);
+	if (! gpiob_spi_driver_setup(&gpiob_spi_drivers[port_index][dout], buf)) {
+		log_error("failed to set up spi driver [%s]", buf);
+		return false;
+	}
+	if (spi_register_driver(&gpiob_spi_drivers[port_index][dout])) {
+		log_error("failed to register accessory card %d dout driver", port);
+		spi_unregister_driver(&gpiob_spi_drivers[port_index][dout]);
+		return false;
+	}
+
+	log_debug("registering accessory card %d din driver", port);
+	sprintf(buf, "mts-io-ap%d-din", port);
+	if (! gpiob_spi_driver_setup(&gpiob_spi_drivers[port_index][din], buf)) {
+		log_error("failed to set up spi driver [%s]", buf);
+		return false;
+	}
+	if (spi_register_driver(&gpiob_spi_drivers[port_index][din])) {
+		log_error("failed to register accessory card %d din driver", port);
+		spi_unregister_driver(&gpiob_spi_drivers[port_index][din]);
+		return false;
+	}
+
+	log_debug("registering accessory card %d adc driver", port);
+	sprintf(buf, "mts-io-ap%d-adc", port);
+	if (! gpiob_spi_driver_setup(&gpiob_spi_drivers[port_index][adc], buf)) {
+		log_error("failed to set up spi driver [%s]", buf);
+		return false;
+	}
+	if (spi_register_driver(&gpiob_spi_drivers[port_index][adc])) {
+		log_error("failed to register accessory card %d adc driver", port);
+		spi_unregister_driver(&gpiob_spi_drivers[port_index][adc]);
+		return false;
+	}
+	return true;
+}
+
+static bool gpiob_teardown(enum ap port) {
+	int port_index = port - 1;
+
+	// do we need to clean up allocated memory here as well?
+	log_info("unloading GPIOB accessory card in port %d", port);
+	spi_unregister_driver(&gpiob_spi_drivers[port_index][dout]);
+	spi_unregister_driver(&gpiob_spi_drivers[port_index][din]);
+	spi_unregister_driver(&gpiob_spi_drivers[port_index][adc]);
+	return true;
+}
 
-/* accessory port 2 gpiob attributes */
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_din0, "din0:1", mts_attr_show_ap_din);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_din1, "din1:1", mts_attr_show_ap_din);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_din2, "din2:1", mts_attr_show_ap_din);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_din3, "din3:1", mts_attr_show_ap_din);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_dout0, "dout0:1", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_dout1, "dout1:1", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_dout2, "dout2:1", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_dout3, "dout3:1", mts_attr_show_ap_dout, mts_attr_store_ap_dout);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_adc0, "adc0:1", mts_attr_show_ap_adc);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_adc1, "adc1:1", mts_attr_show_ap_adc);
-static DEVICE_ATTR_RO_MTS(dev_attr_ap2_gpio_adc2, "adc2:1", mts_attr_show_ap_adc);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_led1, "ap2-led1", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_led2, "ap2-led2", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap2_gpio_oe, "ap2-dout-enable", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap2_reset, "ap2-reset", mts_attr_show_ap_gpio_pin, mts_attr_store_ap_gpio_pin);
-
-static int ap2_gpio_attributes_size = 15;		// not including NULL at end
-
-static struct attribute *ap2_gpio_attributes[] = {
-	&dev_attr_ap2_reset.attr,
-
-	&dev_attr_ap2_gpio_oe.attr,			// gpio1
-	&dev_attr_ap2_gpio_led1.attr,		// gpio3
-	&dev_attr_ap2_gpio_led2.attr,		// gpio4
-
-	&dev_attr_ap2_gpio_din0.attr,
-	&dev_attr_ap2_gpio_din1.attr,
-	&dev_attr_ap2_gpio_din2.attr,
-	&dev_attr_ap2_gpio_din3.attr,
-
-	&dev_attr_ap2_gpio_dout0.attr,
-	&dev_attr_ap2_gpio_dout1.attr,
-	&dev_attr_ap2_gpio_dout2.attr,
-	&dev_attr_ap2_gpio_dout3.attr,
-
-	&dev_attr_ap2_gpio_adc0.attr,
-	&dev_attr_ap2_gpio_adc1.attr,
-	&dev_attr_ap2_gpio_adc2.attr,
-
-	NULL,
+static struct ap_info gpiob_info = {
+	.product_id = MTAC_GPIOB_0_0,
+	.setup = &gpiob_setup,
+	.teardown = &gpiob_teardown
 };
diff --git a/io-module/mtac_mfser.c b/io-module/mtac_mfser.c
index 14eddd1..5871bfe 100644
--- a/io-module/mtac_mfser.c
+++ b/io-module/mtac_mfser.c
@@ -2,13 +2,13 @@ struct gpio_pin *ap_mfser_pin_by_attr_name(const char *name) {
 	struct gpio_pin *pin;
 	char *pin_attr_name;
 
-	if (!strcmp(name, "rs4xx-term-res:0")) {
+	if (!strcmp(name, "rs4xx-term-res:1")) {
 		pin_attr_name = "ap1-gpio3";
-	} else if (!strcmp(name, "rts-override:0")) {
+	} else if (!strcmp(name, "rts-override:1")) {
 		pin_attr_name = "ap1-gpio4";
-	} else if (!strcmp(name, "rs4xx-term-res:1")) {
+	} else if (!strcmp(name, "rs4xx-term-res:2")) {
 		pin_attr_name = "ap2-gpio3";
-	} else if (!strcmp(name, "rts-override:1")) {
+	} else if (!strcmp(name, "rts-override:2")) {
 		pin_attr_name = "ap2-gpio4";
 	} else {
 		log_error("accessory card attribute %s not available", name);
@@ -27,8 +27,8 @@ struct gpio_pin *ap_mfser_pin_by_attr_name(const char *name) {
 }
 
 
-static ssize_t mts_attr_show_ap_mfser_pin(struct device *dev,
-			struct device_attribute *attr,
+static ssize_t mts_attr_show_ap_mfser_pin(struct kobject *kobj,
+			struct kobj_attribute *attr,
 			char *buf)
 {
 	int value;
@@ -55,8 +55,8 @@ static ssize_t mts_attr_show_ap_mfser_pin(struct device *dev,
 	return sprintf(buf, "%d\n", value);
 }
 
-static ssize_t mts_attr_store_ap_mfser_pin(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t count)
+static ssize_t mts_attr_store_ap_mfser_pin(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
 {
 	int value;
 	struct gpio_pin *pin = ap_mfser_pin_by_attr_name(attr->attr.name);
@@ -82,8 +82,8 @@ static ssize_t mts_attr_store_ap_mfser_pin(struct device *dev,
 	return count;
 }
 
-static ssize_t mts_attr_show_mfser_mode(struct device *dev,
-			struct device_attribute *attr,
+static ssize_t mts_attr_show_mfser_mode(struct kobject *kobj,
+			struct kobj_attribute *attr,
 			char *buf)
 {
 	int ret;
@@ -93,11 +93,11 @@ static ssize_t mts_attr_show_mfser_mode(struct device *dev,
 	struct gpio_pin *pin_modesel0;
 	struct gpio_pin *pin_modesel1;
 
-	if (strstr(attr->attr.name, ":0")) {
+	if (strstr(attr->attr.name, ":1")) {
 		pin_modesel0 = gpio_pin_by_name("AP1_GPIO1");
 		pin_modesel1 = gpio_pin_by_name("AP1_GPIO2");
 	}
-	else if (strstr(attr->attr.name, ":1")) {
+	else if (strstr(attr->attr.name, ":2")) {
 		pin_modesel0 = gpio_pin_by_name("AP2_GPIO1");
 		pin_modesel1 = gpio_pin_by_name("AP2_GPIO2");
 	}
@@ -130,19 +130,19 @@ static ssize_t mts_attr_show_mfser_mode(struct device *dev,
 	return ret;
 }
 
-static ssize_t mts_attr_store_mfser_mode(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t count)
+static ssize_t mts_attr_store_mfser_mode(struct kobject *kobj,
+		struct kobj_attribute *attr, const char *buf, size_t count)
 {
 	int modesel0;
 	int modesel1;
 	struct gpio_pin *pin_modesel0;
 	struct gpio_pin *pin_modesel1;
 
-	if (strstr(attr->attr.name, ":0")) {
+	if (strstr(attr->attr.name, ":1")) {
 		pin_modesel0 = gpio_pin_by_name("AP1_GPIO1");
 		pin_modesel1 = gpio_pin_by_name("AP1_GPIO2");
 	}
-	else if (strstr(attr->attr.name, ":1")) {
+	else if (strstr(attr->attr.name, ":2")) {
 		pin_modesel0 = gpio_pin_by_name("AP2_GPIO1");
 		pin_modesel1 = gpio_pin_by_name("AP2_GPIO2");
 	}
@@ -184,32 +184,62 @@ static ssize_t mts_attr_store_mfser_mode(struct device *dev,
 	return count;
 }
 
-/* accessory port 1 serial attributes */
-static DEVICE_ATTR_MTS(dev_attr_ap1_serial_mode, "serial-mode:0", mts_attr_show_mfser_mode, mts_attr_store_mfser_mode);
-static DEVICE_ATTR_MTS(dev_attr_ap1_rs4xx_term_res, "rs4xx-term-res:0", mts_attr_show_ap_mfser_pin, mts_attr_store_ap_mfser_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap1_rts_override, "rts-override:0", mts_attr_show_ap_mfser_pin, mts_attr_store_ap_mfser_pin);
+// 1 serial mode
+// 1 rs4xx term resistor
+// 1 rts override
+static int ap_mfser_attrs_size = 3;
 
-static int ap1_mfser_attributes_size = 3;		// not including NULL at end
+static bool mfser_setup(enum ap port) {
+	struct kobj_attribute *attr;
+	char buf[32];
 
-static struct attribute *ap1_mfser_attributes[] = {
-	&dev_attr_ap1_serial_mode.attr,
-	&dev_attr_ap1_rs4xx_term_res.attr,		// gpio3
-	&dev_attr_ap1_rts_override.attr,		// gpio4
-	NULL,
-};
+	log_info("loading MFSER accessory card in port %d", port);
 
-/* accessory port 2 serial attributes */
-static DEVICE_ATTR_MTS(dev_attr_ap2_serial_mode, "serial-mode:1", mts_attr_show_mfser_mode, mts_attr_store_mfser_mode);
-static DEVICE_ATTR_MTS(dev_attr_ap2_rs4xx_term_res, "rs4xx-term-res:1", mts_attr_show_ap_mfser_pin, mts_attr_store_ap_mfser_pin);
-static DEVICE_ATTR_MTS(dev_attr_ap2_rts_override, "rts-override:1", mts_attr_show_ap_mfser_pin, mts_attr_store_ap_mfser_pin);
+	if (device_attrs_size + ap_mfser_attrs_size >= device_attrs_max_size) {
+		log_error("can't load MFSER accessory card in port %d - not enough room for attributes", port);
+		return false;
+	}
 
-static int ap2_mfser_attributes_size = 3;		// not including NULL at end
+	sprintf(buf, "serial-mode:%d", port);
+	attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+	if (! attr) {
+		log_error("failed to create attribute[%s]", buf);
+		return false;
+	}
+	attr->show = mts_attr_show_mfser_mode;
+	attr->store = mts_attr_store_mfser_mode;
+	device_attrs[device_attrs_size++] = &attr->attr;
 
-static struct attribute *ap2_mfser_attributes[] = {
-	&dev_attr_ap2_serial_mode.attr,
-	&dev_attr_ap2_rs4xx_term_res.attr,		// gpio3
-	&dev_attr_ap2_rts_override.attr,		// gpio4
-	NULL,
-};
+	sprintf(buf, "rs4xx-term-res:%d", port);
+	attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+	if (! attr) {
+		log_error("failed to create attribute[%s]", buf);
+		return false;
+	}
+	attr->show = mts_attr_show_ap_mfser_pin;
+	attr->store = mts_attr_store_ap_mfser_pin;
+	device_attrs[device_attrs_size++] = &attr->attr;
 
+	sprintf(buf, "rts-override:%d", port);
+	attr = create_attribute(buf, MTS_ATTR_MODE_RW);
+	if (! attr) {
+		log_error("failed to create attribute[%s]", buf);
+		return false;
+	}
+	attr->show = mts_attr_show_ap_mfser_pin;
+	attr->store = mts_attr_store_ap_mfser_pin;
+	device_attrs[device_attrs_size++] = &attr->attr;
+
+	return true;
+}
 
+static bool mfser_teardown(enum ap port) {
+	log_info("unloading MFSER accessory card in port %d", port);
+	return true;
+}
+
+static struct ap_info mfser_info = {
+	.product_id = MTAC_MFSER_0_0,
+	.setup = &mfser_setup,
+	.teardown = &mfser_teardown
+};
diff --git a/io-module/mtr2d2.c b/io-module/mtr2d2.c
index 0926952..24a99f3 100644
--- a/io-module/mtr2d2.c
+++ b/io-module/mtr2d2.c
@@ -1,4 +1,3 @@
-
 static struct gpio_pin gpio_pins_mtr2d2_0_0[] = {
 	{
 		.name = "RADIO_RESET",
@@ -266,7 +265,8 @@ static struct gpio_pin gpio_pins_mtr2d2_0_0[] = {
 	{ },
 };
 
-static int mtr2d2_platform_attributes_size = 64;		// not including NULL at end
+static int mtr2d2_platform_attributes_max_size = 64;		// including NULL at end
+static int mtr2d2_platform_attributes_size = 21;
 
 static struct attribute *mtr2d2_platform_attributes[] = {
 	&dev_attr_vendor_id.attr,
@@ -295,6 +295,8 @@ static struct attribute *mtr2d2_platform_attributes[] = {
 	&dev_attr_board_temperature.attr,
 
 	/* extra space for the accessory card attributes */
+	NULL,	    // index 21
+	NULL,	    // index 22
 	NULL,	    // index 23
 	NULL,	    // index 24
 	NULL,	    // index 25
@@ -336,7 +338,6 @@ static struct attribute *mtr2d2_platform_attributes[] = {
 	NULL,	    // index 61
 	NULL,	    // index 62
 	NULL,	    // index 63
-	NULL,	    // index 64
 	NULL,
 };
 
diff --git a/io-module/mts_io.c b/io-module/mts_io.c
index 9adfd12..936d0d2 100644
--- a/io-module/mts_io.c
+++ b/io-module/mts_io.c
@@ -59,24 +59,33 @@
 extern uint8_t mts_id_eeprom[512];
 static struct mts_id_eeprom_layout id_eeprom;
 
-/* accessory card EEPROMs */
-#ifdef MTOCGD2
-extern uint8_t mts_ap1_eeprom[512];
-extern uint8_t mts_ap2_eeprom[512];
+// NUM_AP should be defined from the board code
+// it should be set to the value of CONFIG_MTS_NUM_ACCESSORY_PORTS
+// arch/arm/mach-at91/board-dt-sam9.c
+// if it is 0 or undefined, there is no accessory card support on this HW
+#ifdef CONFIG_MTS_NUM_ACCESSORY_PORTS
+
+#ifndef NUM_AP
+#define NUM_AP CONFIG_MTS_NUM_ACCESSORY_PORTS
+#endif
+
 #else
-uint8_t mts_ap1_eeprom[512] = {};
-uint8_t mts_ap2_eeprom[512] = {};
+#define NUM_AP 0
 #endif
-static struct mts_ap_eeprom_layout ap1_eeprom;
-static struct mts_ap_eeprom_layout ap2_eeprom;
 
-bool accessory_card_capable = false;
-bool have_accessory_card_slot_1 = false;
-bool have_accessory_card_slot_2 = false;
+#if NUM_AP > 0
+/* accessory card EEPROMs */
+extern uint8_t mts_ap_eeprom[NUM_AP][512];
+static struct mts_ap_eeprom_layout ap_eeprom[NUM_AP];
+#endif
+
+static struct ap_info* port_info[NUM_AP];
+
+static struct attribute **device_attrs;
+static size_t device_attrs_size;
+static size_t device_attrs_max_size;
 
 static uint8_t mts_product_id;
-static uint8_t mts_ap1_product_id;
-static uint8_t mts_ap2_product_id;
 static uint8_t has_spi_sout;
 static uint8_t has_spi_din;
 static uint8_t has_spi_dout;
@@ -98,6 +107,7 @@ static DEFINE_MUTEX(mts_io_mutex);
 #include "spi.c"
 
 /* accessory card support */
+#include "mtac.c"
 #include "mtac_gpiob.c"
 #include "mtac_mfser.c"
 
@@ -415,131 +425,57 @@ static DEVICE_ATTR_RO_MTS(dev_attr_eth_mac, "mac-eth",
 #include "mt100eocg.c"
 */
 
-static bool add_accessory_card_attributes(int slot)
-{
-	size_t device_attrs_size;
-	size_t card_attrs_size;
-	size_t attrs_index;
-	size_t i;
-
-	struct attribute **device_attrs;
-	struct attribute **card_attrs;
-
-	switch (mts_product_id) {
-		case MTR2D2_0_0:
-			device_attrs_size = mtr2d2_platform_attributes_size;
-			device_attrs = mtr2d2_platform_attributes;
-			break;
-		default:
-			log_error("accessory cards aren't supported for platform %s", id_eeprom.hw_version);
-			return false;
-	}
+static bool load_port(int port) {
+	int port_index = port - 1;
+	memcpy(&ap_eeprom[port_index], mts_ap_eeprom[port_index], sizeof(mts_ap_eeprom[port_index]));
 
-	if (slot == 1) {
-		switch (mts_ap1_product_id) {
-			case MTAC_GPIOB_0_0:
-				card_attrs_size = ap1_gpio_attributes_size;
-				card_attrs = ap1_gpio_attributes;
-				break;
-			case MTAC_MFSER_0_0:
-				card_attrs_size = ap1_mfser_attributes_size;
-				card_attrs = ap1_mfser_attributes;
-				break;
-			default:
-				log_error("accessory card %s isn't supported", ap1_eeprom.hw_version);
-				return false;
-		}
-	} else if (slot == 2) {
-		switch (mts_ap2_product_id) {
-			case MTAC_GPIOB_0_0:
-				card_attrs_size = ap2_gpio_attributes_size;
-				card_attrs = ap2_gpio_attributes;
-				break;
-			case MTAC_MFSER_0_0:
-				card_attrs_size = ap2_mfser_attributes_size;
-				card_attrs = ap2_mfser_attributes;
-				break;
-			default:
-				log_error("accessory card %s isn't supported", ap2_eeprom.hw_version);
-				return false;
-		}
+	if (mts_ap_eeprom[port_index][0] == 0xFF) {
+		log_error("uninitialized eeprom on accessory card %d", port);
+	} else if (mts_ap_eeprom[port_index][0] == 0x00) {
+		log_info("no accessory card inserted in port %d", port);
 	} else {
-		log_error("%d is an invalid slot value", slot);
-		return false;
-	}
-
-	for (attrs_index = 0; attrs_index < device_attrs_size; attrs_index++) {
-		if (! device_attrs[attrs_index]) {
-			break;
+		if (strstr(ap_eeprom[port_index].product_id, PRODUCT_ID_MTAC_GPIOB)) {
+			port_info[port_index] = &gpiob_info;
+		} else if (strstr(ap_eeprom[port_index].product_id, PRODUCT_ID_MTAC_MFSER)) {
+			port_info[port_index] = &mfser_info;
+		} else {
+			log_error("unknown accessory card [%s] in port %d", ap_eeprom[port_index].product_id, port);
+			return false;
 		}
-	}
 
-	if (device_attrs_size < attrs_index + card_attrs_size) {
-		log_error("not enough room for accessory card attributes!");
-		return false;
-	}
+		log_info("accessory card %d vendor-id: %.32s", port, ap_eeprom[port_index].vendor_id);
+		log_info("accessory card %d product-id: %.32s", port,  ap_eeprom[port_index].product_id);
+		log_info("accessory card %d device-id: %.32s", port,  ap_eeprom[port_index].device_id);
+		log_info("accessory card %d hw-version: %.32s", port,  ap_eeprom[port_index].hw_version);
+		if (strncmp(ap_eeprom[port_index].product_id, PRODUCT_ID_MTAC_ETH, strlen(PRODUCT_ID_MTAC_ETH)) == 0) {
+			log_info("accessory card %d mac-addr: %02X:%02X:%02X:%02X:%02X:%02X",
+			    port,
+			    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]);
+		}
 
-	for (i = 0; i < card_attrs_size; i++) {
-		device_attrs[attrs_index + i] = card_attrs[i];
+		if (! port_info[port_index]->setup(port)) {
+			log_error("accessory port %d setup failed", port);
+			port_info[port_index]->teardown(port);
+			return false;
+		}
 	}
 
 	return true;
 }
 
-static bool mts_ap_eeprom_load(void)
+static void init_accessory_ports(void)
 {
-	// Accessory Card Slot 1
-	memcpy(&ap1_eeprom, mts_ap1_eeprom, sizeof(mts_ap1_eeprom));
-
-	if (mts_ap1_eeprom[0] == 0xFF) {
-		log_error("uninitialized eeprom on accessory card 1");
-	} else if (mts_ap1_eeprom[0] == 0x00) {
-		log_info("no accessory card inserted in slot 1");
-	} else {
-		have_accessory_card_slot_1 = true;
-
-		log_info("accessory card 1 vendor-id: %.32s", ap1_eeprom.vendor_id);
-		log_info("accessory card 1 product-id: %.32s",  ap1_eeprom.product_id);
-		log_info("accessory card 1 device-id: %.32s",  ap1_eeprom.device_id);
-		log_info("accessory card 1 hw-version: %.32s",  ap1_eeprom.hw_version);
-		if (strncmp(ap1_eeprom.product_id, PRODUCT_ID_MTAC_ETH, strlen(PRODUCT_ID_MTAC_ETH)) == 0) {
-			log_info("accessory card 1 mac-addr: %02X:%02X:%02X:%02X:%02X:%02X",
-			    ap1_eeprom.mac_addr[0],
-			    ap1_eeprom.mac_addr[1],
-			    ap1_eeprom.mac_addr[2],
-			    ap1_eeprom.mac_addr[3],
-			    ap1_eeprom.mac_addr[4],
-			    ap1_eeprom.mac_addr[5]);
-		}
-	}
-
-	// Accessory Card Slot 2
-	memcpy(&ap2_eeprom, mts_ap2_eeprom, sizeof(mts_ap2_eeprom));
-
-	if (mts_ap2_eeprom[0] == 0xFF) {
-		log_error("uninitialized eeprom on accessory card 2");
-	} else if (mts_ap2_eeprom[0] == 0x00) {
-		log_info("no accessory card inserted in slot 2");
-	} else {
-		have_accessory_card_slot_2 = true;
-
-		log_info("accessory card 2 vendor-id: %.32s", ap2_eeprom.vendor_id);
-		log_info("accessory card 2 product-id: %.32s",  ap2_eeprom.product_id);
-		log_info("accessory card 2 device-id: %.32s",  ap2_eeprom.device_id);
-		log_info("accessory card 2 hw-version: %.32s",  ap2_eeprom.hw_version);
-		if (strncmp(ap2_eeprom.product_id, PRODUCT_ID_MTAC_ETH, strlen(PRODUCT_ID_MTAC_ETH)) == 0) {
-			log_info("accessory card 2 mac-addr: %02X:%02X:%02X:%02X:%02X:%02X",
-			    ap2_eeprom.mac_addr[0],
-			    ap2_eeprom.mac_addr[1],
-			    ap2_eeprom.mac_addr[2],
-			    ap2_eeprom.mac_addr[3],
-			    ap2_eeprom.mac_addr[4],
-			    ap2_eeprom.mac_addr[5]);
+	int i;
+	for (i = 1; i <= NUM_AP; i++) {
+		if (! load_port(i)) {
+			log_error("failed to load accessory card in port %d", i);
 		}
 	}
-
-	// if either slot has a valid card, return true
-	return (have_accessory_card_slot_1 || have_accessory_card_slot_2);
 }
 
 static int mts_id_eeprom_load(void)
@@ -581,7 +517,6 @@ static int mts_id_eeprom_load(void)
 		attr_group = &mtr2_platform_attribute_group;
 		gpio_pins = gpio_pins_mtr2_0_0;
 		mts_product_id = MTR2_0_0;
-		accessory_card_capable = true;
 		has_spi_sout = 0;
 		has_spi_din = 0;
 		has_spi_dout = 0;
@@ -611,7 +546,6 @@ static int mts_id_eeprom_load(void)
 		attr_group = &mtr2_platform_attribute_group;
 		gpio_pins = gpio_pins_mtr2_0_0;
 		mts_product_id = MTOCGD2_0_0;
-		accessory_card_capable = true;
 		has_spi_sout = 0;
 		has_spi_din = 0;
 		has_spi_dout = 0;
@@ -637,10 +571,15 @@ static int mts_id_eeprom_load(void)
 		has_spi_temp = 0;
 		log_info("detected board %s", HW_VERSION_MTOCGD_0_1);
 	} else if (strncmp(id_eeprom.hw_version, HW_VERSION_MTR2D2_0_0, strlen(HW_VERSION_MTR2D2_0_0)) == 0) {
+		// need to put any accessory card attributes into this list so they show up in sysfs
+		// the port_info->setup callback does this
+		device_attrs = mtr2d2_platform_attributes;
+		device_attrs_size = mtr2d2_platform_attributes_size;
+		device_attrs_max_size = mtr2d2_platform_attributes_max_size;
+
 		attr_group = &mtr2d2_platform_attribute_group;
 		gpio_pins = gpio_pins_mtr2d2_0_0;
 		mts_product_id = MTR2D2_0_0;
-		accessory_card_capable = true;
 		has_spi_sout = 0;
 		has_spi_din = 0;
 		has_spi_dout = 0;
@@ -706,6 +645,7 @@ static int __init mts_io_init(void)
 	int ret;
 	size_t device_attributes_size;
 	size_t card_attributes_size;
+	int i;
 
 	log_info("init: " DRIVER_VERSION);
 	
@@ -714,118 +654,11 @@ static int __init mts_io_init(void)
 		goto error1;
 	}
 
-	if (accessory_card_capable) {
-		mts_ap1_product_id = MTAC_NONE;
-		mts_ap2_product_id = MTAC_NONE;
-		if (mts_ap_eeprom_load()) {
-			// handle both slots, but do slot 1 first
-			// probably need special handling if both cards are the same type
-			if (have_accessory_card_slot_1) {
-				// more elegant way to handle this?
-				if (strstr(ap1_eeprom.product_id, PRODUCT_ID_MTAC_GPIOB)) {
-					mts_ap1_product_id = MTAC_GPIOB_0_0;
-				}
-				else if (strstr(ap1_eeprom.product_id, PRODUCT_ID_MTAC_MFSER)) {
-					mts_ap1_product_id = MTAC_MFSER_0_0;
-				}
-
-				switch(mts_ap1_product_id) {
-					case MTAC_GPIOB_0_0:
-						log_info("loading GPIO accessory card in slot 1");
-						if (! add_accessory_card_attributes(1)) {
-							log_error("failed to load GPIO accessory card in slot 1");
-						} else {
-							log_info("successfully loaded GPIO accessory card in slot 1");
-						}
-						log_debug("registering accessory card 1 dout driver");
-						ret = spi_register_driver(&mts_spi_ap1_dout_driver);
-						if (ret) {
-							log_error("failed to register accessory card 1 dout driver");
-							spi_unregister_driver(&mts_spi_ap1_dout_driver);
-							goto error1;
-						}
-						log_debug("registering accessory card 1 din driver");
-						ret = spi_register_driver(&mts_spi_ap1_din_driver);
-						if (ret) {
-							log_error("failed to register accessory card 1 din driver");
-							spi_unregister_driver(&mts_spi_ap1_din_driver);
-							goto error1;
-						}
-						log_debug("registering accessory card 1 adc driver");
-						ret = spi_register_driver(&mts_spi_ap1_adc_driver);
-						if (ret) {
-							log_error("failed to register accessory card 1 adc driver");
-							spi_unregister_driver(&mts_spi_ap1_adc_driver);
-							goto error1;
-						}
-						break;
-					case MTAC_MFSER_0_0:
-						log_info("loading MFSER accessory card in slot 1");
-						if (! add_accessory_card_attributes(1)) {
-							log_error("failed to load MFSER accessory card in slot 1");
-						} else {
-							log_info("successfully loaded MFSER accessory card in slot 1");
-						}
-						break;
-
-					default:
-						log_error("accessory card %s unsupported", ap1_eeprom.product_id);
-				}
-			}
-
-			if (have_accessory_card_slot_2) {
-				// more elegant way to handle this?
-				if (strstr(ap2_eeprom.product_id, PRODUCT_ID_MTAC_GPIOB)) {
-					mts_ap2_product_id = MTAC_GPIOB_0_0;
-				}
-				else if (strstr(ap2_eeprom.product_id, PRODUCT_ID_MTAC_MFSER)) {
-					mts_ap2_product_id = MTAC_MFSER_0_0;
-				}
-
-				switch(mts_ap2_product_id) {
-					case MTAC_GPIOB_0_0:
-						log_info("loading GPIO accessory card in slot 2");
-						if (! add_accessory_card_attributes(2)) {
-							log_error("failed to load GPIO accessory card in slot 2");
-						} else {
-							log_info("successfully loaded GPIO accessory card in slot 2");
-						}
-						log_debug("registering accessory card 2 dout driver");
-						ret = spi_register_driver(&mts_spi_ap2_dout_driver);
-						if (ret) {
-							log_error("failed to register accessory card 2 dout driver");
-							spi_unregister_driver(&mts_spi_ap2_dout_driver);
-							goto error1;
-						}
-						log_debug("registering accessory card 2 din driver");
-						ret = spi_register_driver(&mts_spi_ap2_din_driver);
-						if (ret) {
-							log_error("failed to register accessory card 2 din driver");
-							spi_unregister_driver(&mts_spi_ap2_din_driver);
-							goto error1;
-						}
-						log_debug("registering accessory card 2 adc driver");
-						ret = spi_register_driver(&mts_spi_ap2_adc_driver);
-						if (ret) {
-							log_error("failed to register accessory card 2 adc driver");
-							spi_unregister_driver(&mts_spi_ap2_adc_driver);
-							goto error1;
-						}
-						break;
-					case MTAC_MFSER_0_0:
-						log_info("loading MFSER accessory card in slot 2");
-						if (! add_accessory_card_attributes(2)) {
-							log_error("failed to load MFSER accessory card in slot 2");
-						} else {
-							log_info("successfully loaded MFSER accessory card in slot 2");
-						}
-						break;
-
-					default:
-						log_error("accessory card %s unsupported", ap1_eeprom.product_id);
-				}
-			}
+	if (NUM_AP) {
+		for (i = 0; i < NUM_AP; i++) {
+			port_info[i] = NULL;
 		}
+		init_accessory_ports();
 	}
 
 	mts_io_platform_device = platform_device_alloc(PLATFORM_NAME, -1);
@@ -950,40 +783,21 @@ error3:
 	platform_device_del(mts_io_platform_device);
 error2:
 	platform_device_put(mts_io_platform_device);
-
-	if (have_accessory_card_slot_1) {
-		switch (mts_ap1_product_id) {
-			case MTAC_GPIOB_0_0:
-				spi_unregister_driver(&mts_spi_ap1_dout_driver);
-				spi_unregister_driver(&mts_spi_ap1_din_driver);
-				spi_unregister_driver(&mts_spi_ap1_adc_driver);
-				break;
-
-			default:
-				break;
-		}
-	}
-
-	if (have_accessory_card_slot_2) {
-		switch (mts_ap2_product_id) {
-			case MTAC_GPIOB_0_0:
-				spi_unregister_driver(&mts_spi_ap2_dout_driver);
-				spi_unregister_driver(&mts_spi_ap2_din_driver);
-				spi_unregister_driver(&mts_spi_ap2_adc_driver);
-				break;
-
-			default:
-				break;
-		}
-	}
 error1:
 	log_error("init failed: %d", ret);
+	for (i = 0; i < NUM_AP; i++) {
+		if (port_info[i]) {
+			port_info[i]->teardown(i);
+		}
+	}
 
 	return ret;
 }
 
 static void __exit mts_io_exit(void)
 {
+	int i;
+
 	if ( mts_product_id != MT100EOCG_0_0 ) {
 		cancel_delayed_work_sync(&reset_work);
 	}
@@ -1004,38 +818,18 @@ static void __exit mts_io_exit(void)
 	if (has_spi_sout)
 		spi_unregister_driver(&mts_spi_sout_driver);
 
-	if (have_accessory_card_slot_1) {
-		switch (mts_ap1_product_id) {
-			case MTAC_GPIOB_0_0:
-				spi_unregister_driver(&mts_spi_ap1_dout_driver);
-				spi_unregister_driver(&mts_spi_ap1_din_driver);
-				spi_unregister_driver(&mts_spi_ap1_adc_driver);
-				break;
-
-			default:
-				break;
-		}
-	}
-
-	if (have_accessory_card_slot_2) {
-		switch (mts_ap2_product_id) {
-			case MTAC_GPIOB_0_0:
-				spi_unregister_driver(&mts_spi_ap2_dout_driver);
-				spi_unregister_driver(&mts_spi_ap2_din_driver);
-				spi_unregister_driver(&mts_spi_ap2_adc_driver);
-				break;
-
-			default:
-				break;
-		}
-	}
-
 	sysfs_remove_group(&mts_io_platform_device->dev.kobj, attr_group);
 
 	sysfs_remove_link(&mts_io_platform_device->dev.parent->kobj, "mtcdp");
 
 	platform_device_unregister(mts_io_platform_device);
 
+	for (i = 0; i < NUM_AP; i++) {
+		if (port_info[i]) {
+			port_info[i]->teardown(i);
+		}
+	}
+
 	log_info("exiting");
 }
 
diff --git a/io-module/mts_io.h b/io-module/mts_io.h
index b91423e..ac39463 100644
--- a/io-module/mts_io.h
+++ b/io-module/mts_io.h
@@ -102,5 +102,25 @@ enum {
 	LED_FLASHING,
 };
 
+enum ap {
+	port_1 = 1,
+	port_2,
+};
+
+enum spi_devices {
+	din = 0,
+	dout = 1,
+	adc = 2,
+};
+
+// info for accessory port
+// contains function pointers for setup and teardown and useful info
+// each type of accessory card should have one of these
+struct ap_info {
+	uint8_t product_id;
+	bool (*setup)(enum ap port);
+	bool (*teardown)(enum ap port);
+};
+
 #endif /* ~__MTS_IO_H */
 
diff --git a/io-module/spi.c b/io-module/spi.c
index e652b90..210371c 100644
--- a/io-module/spi.c
+++ b/io-module/spi.c
@@ -40,35 +40,6 @@ MODULE_PARM_DESC(
 	"Maximum clock rate to be used with this device (default: 1 MHz)"
 );
 
-static struct spi_device *spi_ap1_dout_dev;
-static struct spi_device *spi_ap2_dout_dev;
-static u8 spi_ap_dout_value;
-static DEFINE_MUTEX(spi_ap_dout_mutex);
-static unsigned int ap_dout_max_speed_hz = 1 * 1000 * 1000;
-module_param(ap_dout_max_speed_hz, uint, S_IRUGO);
-MODULE_PARM_DESC(
-	ap_dout_max_speed_hz,
-	"Maximum clock rate to be used with this device (default: 1 MHz)"
-);
-
-static struct spi_device *spi_ap1_din_dev;
-static struct spi_device *spi_ap2_din_dev;
-static unsigned int ap_din_max_speed_hz = 1 * 1000 * 1000;
-module_param(ap_din_max_speed_hz, uint, S_IRUGO);
-MODULE_PARM_DESC(
-	ap_din_max_speed_hz,
-	"Maximum clock rate to be used with this device (default: 1 MHz)"
-);
-
-static struct spi_device *spi_ap1_adc_dev;
-static struct spi_device *spi_ap2_adc_dev;
-static unsigned int ap_adc_max_speed_hz = 20 * 1000 * 1000;
-module_param(ap_adc_max_speed_hz, uint, S_IRUGO);
-MODULE_PARM_DESC(
-	ap_adc_max_speed_hz,
-	"Maximum clock rate to be used with this device (default: 20 MHz)"
-);
-
 static struct spi_device *spi_board_temp_dev;
 static unsigned int board_temp_max_speed_hz = 1 * 1000 * 1000;
 module_param(board_temp_max_speed_hz, uint, S_IRUGO);
@@ -598,272 +569,6 @@ static struct spi_driver mts_spi_din_driver = {
 	.remove = mts_spi_din_remove,
 };
 
-static int mts_spi_ap1_dout_probe(struct spi_device *spi)
-{
-	int tmp;
-
-	if (! have_accessory_card_slot_1 || mts_ap1_product_id != MTAC_GPIOB_0_0) {
-		log_error("accessory card 1 digital outputs not available");
-		return -ENODEV;
-	}
-
-	spi->max_speed_hz = ap_dout_max_speed_hz;
-	spi->mode = 0;
-
-	log_debug("ap1_dout_max_speed_hz: %d", ap_dout_max_speed_hz);
-
-	tmp = spi_setup(spi);
-	if (tmp < 0) {
-		log_error("spi_setup accessory card 1 dout failed");
-		return tmp;
-	}
-
-	spi_ap_dout_value = 0x00;
-	spi_writen(spi, &spi_ap_dout_value, 1);
-
-	spi_ap1_dout_dev = spi;
-
-	return 0;
-}
-
-static int mts_spi_ap1_dout_remove(struct spi_device *spi)
-{
-	spi_ap1_dout_dev = NULL;
-
-	return 0;
-}
-
-static struct spi_driver mts_spi_ap1_dout_driver = {
-	.driver = {
-		.name = "mts-io-ap1-dout",
-		.bus = &spi_bus_type,
-		.owner = THIS_MODULE,
-	},
-
-	.probe = mts_spi_ap1_dout_probe,
-	.remove = mts_spi_ap1_dout_remove,
-};
-
-static int mts_spi_ap1_din_probe(struct spi_device *spi)
-{
-	int tmp;
-
-	if (! have_accessory_card_slot_1 || mts_ap1_product_id != MTAC_GPIOB_0_0) {
-		log_error("accessory card 1 digital inputs not available");
-		return -ENODEV;
-	}
-
-	spi->max_speed_hz = ap_din_max_speed_hz;
-	spi->mode = SPI_CPOL;
-
-	log_debug("ap1_din_max_speed_hz: %d", ap_din_max_speed_hz);
-
-	tmp = spi_setup(spi);
-	if (tmp < 0) {
-		log_error("spi_setup accessory card 1 din failed");
-		return tmp;
-	}
-
-	spi_ap1_din_dev = spi;
-
-	return 0;
-}
-
-static int mts_spi_ap1_din_remove(struct spi_device *spi)
-{
-	spi_ap1_din_dev = NULL;
-
-	return 0;
-}
-
-static struct spi_driver mts_spi_ap1_din_driver = {
-	.driver = {
-		.name = "mts-io-ap1-din",
-		.bus = &spi_bus_type,
-		.owner = THIS_MODULE,
-	},
-
-	.probe = mts_spi_ap1_din_probe,
-	.remove = mts_spi_ap1_din_remove,
-};
-
-static int mts_spi_ap1_adc_probe(struct spi_device *spi)
-{
-	int tmp;
-
-	if (! have_accessory_card_slot_1 || mts_ap1_product_id != MTAC_GPIOB_0_0) {
-		log_error("accessory card 1 analog to digital not available");
-		return -ENODEV;
-	}
-
-	spi->max_speed_hz = ap_adc_max_speed_hz;
-	spi->mode = 0;
-
-	log_debug("ap1_adc_max_speed_hz: %d", ap_adc_max_speed_hz);
-	log_debug("ap1_adc_mode: %d", spi->mode);
-
-	tmp = spi_setup(spi);
-	if (tmp < 0) {
-		log_error("spi_setup accessory card 1 adc failed");
-		return tmp;
-	}
-
-	spi_ap1_adc_dev = spi;
-
-	return 0;
-}
-
-static int mts_spi_ap1_adc_remove(struct spi_device *spi)
-{
-	spi_ap1_adc_dev = NULL;
-
-	return 0;
-}
-
-static struct spi_driver mts_spi_ap1_adc_driver = {
-	.driver = {
-		.name = "mts-io-ap1-adc",
-		.bus = &spi_bus_type,
-		.owner = THIS_MODULE,
-	},
-
-	.probe = mts_spi_ap1_adc_probe,
-	.remove = mts_spi_ap1_adc_remove,
-};
-
-static int mts_spi_ap2_dout_probe(struct spi_device *spi)
-{
-	int tmp;
-
-	if (! have_accessory_card_slot_2 || mts_ap2_product_id != MTAC_GPIOB_0_0) {
-		log_error("accessory card 2 digital outputs not available");
-		return -ENODEV;
-	}
-
-	spi->max_speed_hz = ap_dout_max_speed_hz;
-	spi->mode = 0;
-
-	log_debug("ap2_dout_max_speed_hz: %d", ap_dout_max_speed_hz);
-
-	tmp = spi_setup(spi);
-	if (tmp < 0) {
-		log_error("spi_setup accessory card 2 dout failed");
-		return tmp;
-	}
-
-	spi_ap_dout_value = 0x00;
-	spi_writen(spi, &spi_ap_dout_value, 2);
-
-	spi_ap2_dout_dev = spi;
-
-	return 0;
-}
-
-static int mts_spi_ap2_dout_remove(struct spi_device *spi)
-{
-	spi_ap2_dout_dev = NULL;
-
-	return 0;
-}
-
-static struct spi_driver mts_spi_ap2_dout_driver = {
-	.driver = {
-		.name = "mts-io-ap2-dout",
-		.bus = &spi_bus_type,
-		.owner = THIS_MODULE,
-	},
-
-	.probe = mts_spi_ap2_dout_probe,
-	.remove = mts_spi_ap2_dout_remove,
-};
-
-static int mts_spi_ap2_din_probe(struct spi_device *spi)
-{
-	int tmp;
-
-	if (! have_accessory_card_slot_2 || mts_ap2_product_id != MTAC_GPIOB_0_0) {
-		log_error("accessory card 2 digital inputs not available");
-		return -ENODEV;
-	}
-
-	spi->max_speed_hz = ap_din_max_speed_hz;
-	spi->mode = SPI_CPOL;
-
-	log_debug("ap2_din_max_speed_hz: %d", ap_din_max_speed_hz);
-
-	tmp = spi_setup(spi);
-	if (tmp < 0) {
-		log_error("spi_setup accessory card 2 din failed");
-		return tmp;
-	}
-
-	spi_ap2_din_dev = spi;
-
-	return 0;
-}
-
-static int mts_spi_ap2_din_remove(struct spi_device *spi)
-{
-	spi_ap2_din_dev = NULL;
-
-	return 0;
-}
-
-static struct spi_driver mts_spi_ap2_din_driver = {
-	.driver = {
-		.name = "mts-io-ap2-din",
-		.bus = &spi_bus_type,
-		.owner = THIS_MODULE,
-	},
-
-	.probe = mts_spi_ap2_din_probe,
-	.remove = mts_spi_ap2_din_remove,
-};
-
-static int mts_spi_ap2_adc_probe(struct spi_device *spi)
-{
-	int tmp;
-
-	if (! have_accessory_card_slot_2 || mts_ap2_product_id != MTAC_GPIOB_0_0) {
-		log_error("accessory card 2 analog to digital not available");
-		return -ENODEV;
-	}
-
-	spi->max_speed_hz = ap_adc_max_speed_hz;
-	spi->mode = 0;
-
-	log_debug("ap2_adc_max_speed_hz: %d", ap_adc_max_speed_hz);
-	log_debug("ap2_adc_mode: %d", spi->mode);
-
-	tmp = spi_setup(spi);
-	if (tmp < 0) {
-		log_error("spi_setup accessory card 2 adc failed");
-		return tmp;
-	}
-
-	spi_ap2_adc_dev = spi;
-
-	return 0;
-}
-
-static int mts_spi_ap2_adc_remove(struct spi_device *spi)
-{
-	spi_ap2_adc_dev = NULL;
-
-	return 0;
-}
-
-static struct spi_driver mts_spi_ap2_adc_driver = {
-	.driver = {
-		.name = "mts-io-ap2-adc",
-		.bus = &spi_bus_type,
-		.owner = THIS_MODULE,
-	},
-
-	.probe = mts_spi_ap2_adc_probe,
-	.remove = mts_spi_ap2_adc_remove,
-};
-
 static int mts_spi_board_temp_probe(struct spi_device *spi)
 {
 	int tmp;