USB: cdc_acm: Silence "It is not a modem." error for pbLua devices

The pbLua console port is known to not be a modem, so it is
unnecessary to be told this when it is plugged in.

Add NOT_A_MODEM quirk to tell the driver that we know this already
and hence not to warn us, and mark the pbLua console port.

Signed-off-by: Julian Calaby <julian.calaby@gmail.com>
Cc: Oliver Neukum <oliver@neukum.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/usb/class/cdc-acm.c

@@ -1010,7 +1010,7 @@ static int acm_probe(struct usb_interface *intf,
 		case USB_CDC_CALL_MANAGEMENT_TYPE:
 			call_management_function = buffer[3];
 			call_interface_num = buffer[4];
-			if ((call_management_function & 3) != 3)
+			if ( (quirks & NOT_A_MODEM) == 0 && (call_management_function & 3) != 3)
 				dev_err(&intf->dev, "This device cannot do calls on its own. It is not a modem.\n");
 			break;
 		default:
@@ -1595,7 +1595,9 @@ static struct usb_device_id acm_ids[] = {
 	/* NOTE: non-Nokia COMM/ACM/0xff is likely MSFT RNDIS... NOT a modem! */
 
 	/* Support Lego NXT using pbLua firmware */
-	{ USB_DEVICE(0x0694, 0xff00), },
+	{ USB_DEVICE(0x0694, 0xff00),
+	.driver_info = NOT_A_MODEM,
+       	},
 
 	/* control interfaces with various AT-command sets */
 	{ USB_INTERFACE_INFO(USB_CLASS_COMM, USB_CDC_SUBCLASS_ACM,

drivers/usb/class/cdc-acm.h

@@ -136,3 +136,4 @@ struct acm {
 #define NO_UNION_NORMAL			1
 #define SINGLE_RX_URB			2
 #define NO_CAP_LINE			4
+#define NOT_A_MODEM			8