diff --git a/README.md b/README.md
index 6142aad..47b87b7 100644
--- a/README.md
+++ b/README.md
@@ -230,6 +230,7 @@ libco is licensed under the [ISC license](https://opensource.org/licenses/ISC)
 ## TODO
 
 - [ ] A name
+- [ ] A (VID and) PID, and maybe better subclass & protocol IDs for the vnd cfg itf
 - [x] CMSIS-DAP JTAG implementation
 - [x] Flashrom/SPI support using Serprog
   - Parallel ROM flashing support, too, by having the device switch into a
@@ -254,7 +255,7 @@ libco is licensed under the [ISC license](https://opensource.org/licenses/ISC)
       it'll be used for other stuff anyway, etc.). Means a custom Linux driver but
       oh well, I2C-Tiny-USB needs patching either way.
 - [ ] 1-wire using ↑
-- [ ] A proper interface for sending commands etc. instead of shoehorning it
+- [x] A proper interface for sending commands etc. instead of shoehorning it
       into Serprog.
   - Can probably be included in the "Better USB interface stuff".
 - [ ] JTAG pinout detector
diff --git a/host/modules/dmj.c b/host/modules/dmj.c
index 4e144ca..c20f01c 100644
--- a/host/modules/dmj.c
+++ b/host/modules/dmj.c
@@ -287,10 +287,14 @@ static int dmj_check_hw(struct dmj_dev *dmj)
 	ret = dmj_xfer_internal(dmj, DMJ_CMD_CFG_GET_VERSION,
 			DMJ_XFER_FLAGS_PARSE_RESP, NULL, 0, &protover, &len);
 
-	if (ret < 0) { /* TODO: positive error codes from respstat */
+	if (ret < 0) {
 		dev_err(dev, "USB fail: %d\n", ret);
 		return ret;
 	}
+	if (ret) {
+		dev_err(dev, "USB protocol fail: %s (%d)\n", dmj_get_protoerr(ret), ret);
+		return -EIO;
+	}
 	if (len < sizeof(protover)) {
 		dev_err(dev, "USB fail remoteio: %d\n", len);
 		return -EREMOTEIO;
@@ -321,7 +325,11 @@ static int dmj_print_info(struct dmj_dev *dmj)
 	len = sizeof(strinfo)-1;
 	ret = dmj_xfer_internal(dmj, DMJ_CMD_CFG_GET_INFOSTR,
 			DMJ_XFER_FLAGS_PARSE_RESP, NULL, 0, strinfo, &len);
-	if (ret < 0) return ret; /* TODO: positive error codes from respstat */
+	if (ret < 0) return ret;
+	if (ret) {
+		dev_err(dev, "USB protocol fail: %s (%d)\n", dmj_get_protoerr(ret), ret);
+		return -EIO;
+	}
 	if (len >= sizeof(strinfo)) return -EMSGSIZE;
 	strinfo[len] = 0; /*strinfo[64] = 0;*/
 	dev_info(dev, HARDWARE_NAME " '%s'\n", strinfo);
@@ -418,32 +426,35 @@ static const struct mfd_cell dmj_mfd_i2c[] = {
 static int dmj_probe(struct usb_interface *itf, const struct usb_device_id *usb_id)
 {
 	struct usb_host_interface *hostitf = itf->cur_altsetting;
-	struct usb_endpoint_descriptor *epin, *epout;
+	struct usb_endpoint_descriptor *epin = NULL, *epout = NULL, *curep;
 	struct device *dev = &itf->dev;
 	struct dmj_dev *dmj;
-	int ret;
+	int ret, i;
 
-	/*dev_dbg(dev, "dmj probe itfn=%d nendp=%d\n",
-		hostitf->desc.bInterfaceNumber, hostitf->desc.bNumEndpoints);*/
-
-	if (hostitf->desc.bInterfaceNumber != 0 || hostitf->desc.bNumEndpoints < 2)
+	if (hostitf->desc.bNumEndpoints < 2)
 		return -ENODEV;
 
-	/* TODO: query endpoints in a better way */
-	epout = &hostitf->endpoint[DMJ_VND_CFG_EP_OUT].desc;
-	epin = &hostitf->endpoint[DMJ_VND_CFG_EP_IN].desc;
+	for (i = 0; i < hostitf->desc.bNumEndpoints; ++i) {
+		curep = &hostitf->endpoint[i].desc;
 
-	/*dev_dbg(dev, "epout addr=0x%02x, epin addr=0x%02x\n",
-			epout->bEndpointAddress, epin->bEndpointAddress);*/
+		if (!epin  && usb_endpoint_is_bulk_in (curep)) epin  = curep;
+		if (!epout && usb_endpoint_is_bulk_out(curep)) epout = curep;
 
-	if (!usb_endpoint_is_bulk_out(epout)) { dev_warn(dev, "aaa1\n"); return -ENODEV; }
-	if (!usb_endpoint_is_bulk_in(epin)) { dev_warn(dev, "aaa1\n"); return -ENODEV; }
+		if (epin && epout) break;
+	}
+
+	if (!epin) {
+		dev_warn(dev, "found suitable device but no ep in\n");
+		return -ENODEV;
+	}
+	if (!epout) {
+		dev_warn(dev, "found suitable device but no ep out\n");
+		return -ENODEV;
+	}
 
 	dmj = kzalloc(sizeof(*dmj), GFP_KERNEL);
 	if (!dmj) return -ENOMEM;
 
-	/*dev_dbg(dev, "hi there!\n");*/
-
 	dmj->ep_out = epout->bEndpointAddress;
 	dmj->ep_in = epin->bEndpointAddress;
 	dmj->usb_dev = usb_get_dev(interface_to_usbdev(itf));
@@ -525,7 +536,7 @@ static int dmj_resume(struct usb_interface *itf)
 }
 
 static const struct usb_device_id dmj_table[] = {
-	{ USB_DEVICE(0xcafe, 0x1312) },
+	{ USB_DEVICE_AND_INTERFACE_INFO(0xcafe, 0x1312, USB_CLASS_VENDOR_SPEC, 42, 69) },
 	{ }
 };
 MODULE_DEVICE_TABLE(usb, dmj_table);
diff --git a/src/m_default/_default.c b/src/m_default/_default.c
index f29ea2d..166ab84 100644
--- a/src/m_default/_default.c
+++ b/src/m_default/_default.c
@@ -164,7 +164,6 @@ static void handle_cmd_cb(uint8_t cmd) {
 #define TUD_I2CTINYUSB_DESCRIPTOR(_itfnum, _stridx) \
     9, TUSB_DESC_INTERFACE, _itfnum, 0, 0, 0, 0, 0, _stridx \
 
-
 enum {
     STRID_LANGID = 0,
     STRID_MANUFACTURER,
@@ -264,8 +263,8 @@ static const uint8_t desc_configuration[] = {
         TUSB_DESC_CONFIG_ATT_REMOTE_WAKEUP, 100),
 
 #if CFG_TUD_VENDOR > 0
-    TUD_VENDOR_DESCRIPTOR(ITF_NUM_VND_CFG, STRID_IF_VND_CFG, EPNUM_VND_CFG_OUT,
-        EPNUM_VND_CFG_IN, CFG_TUD_VENDOR_RX_BUFSIZE),
+    TUD_VENDOR_DESCRIPTOR_EX(ITF_NUM_VND_CFG, STRID_IF_VND_CFG, EPNUM_VND_CFG_OUT,
+        EPNUM_VND_CFG_IN, CFG_TUD_VENDOR_RX_BUFSIZE, VND_CFG_SUBCLASS, VND_CFG_PROTOCOL),
 #endif
 
 #if defined(DBOARD_HAS_I2C) && defined(MODE_ENABLE_I2CTINYUSB)
diff --git a/src/vnd_cfg.h b/src/vnd_cfg.h
index f139ab9..57fa591 100644
--- a/src/vnd_cfg.h
+++ b/src/vnd_cfg.h
@@ -5,8 +5,18 @@
 
 #include <stdint.h>
 
-/* the configuration vendor interface must always be the first vendor itf, and
- * have endpoint number 1. */
+/* the configuration vendor interface has a specific subclass and protocol
+ * number that can be useful for identification */
+#define VND_CFG_SUBCLASS 42
+#define VND_CFG_PROTOCOL 69
+#define TUD_VENDOR_DESCRIPTOR_EX(_itfnum, _stridx, _epout, _epin, _epsize, _subclass, _protocol) \
+  /* Interface */\
+  9, TUSB_DESC_INTERFACE, _itfnum, 0, 2, TUSB_CLASS_VENDOR_SPECIFIC, _subclass, _protocol, _stridx,\
+  /* Endpoint Out */\
+  7, TUSB_DESC_ENDPOINT, _epout, TUSB_XFER_BULK, U16_TO_U8S_LE(_epsize), 0,\
+  /* Endpoint In */\
+  7, TUSB_DESC_ENDPOINT, _epin, TUSB_XFER_BULK, U16_TO_U8S_LE(_epsize), 0
+
 
 #define VND_CFG_PROTO_VER 0x0010