USB: serial: pl2303: tighten type HXN (G) detection

Tighten the detection of the new HXN (G) type instead of assuming that
every device which doesn't support the old read request is an HXN.
Signed-off-by: Johan Hovold <johan@kernel.org>

drivers/usb/serial/pl2303.c

@@ -374,12 +374,22 @@ static int pl2303_calc_num_ports(struct usb_serial *serial,
 	return 1;
 }
 
+static bool pl2303_supports_hx_status(struct usb_serial *serial)
+{
+	int ret;
+	u8 buf;
+
+	ret = usb_control_msg_recv(serial->dev, 0, VENDOR_READ_REQUEST,
+			VENDOR_READ_REQUEST_TYPE, PL2303_READ_TYPE_HX_STATUS,
+			0, &buf, 1, 100, GFP_KERNEL);
+
+	return ret == 0;
+}
+
 static int pl2303_detect_type(struct usb_serial *serial)
 {
 	struct usb_device_descriptor *desc = &serial->dev->descriptor;
 	u16 bcdDevice, bcdUSB;
-	int ret;
-	u8 buf;
 
 	/*
 	 * Legacy PL2303H, variants 0 and 1 (difference unknown).
@@ -394,20 +404,18 @@ static int pl2303_detect_type(struct usb_serial *serial)
 		return TYPE_H;		/* variant 0 */
 	}
 
-	/*
-	 * Assume it's an HXN-type if the device doesn't support the old read
-	 * request value.
-	 */
-	ret = usb_control_msg_recv(serial->dev, 0, VENDOR_READ_REQUEST,
-			VENDOR_READ_REQUEST_TYPE, PL2303_READ_TYPE_HX_STATUS,
-			0, &buf, 1, 100, GFP_KERNEL);
-	if (ret)
-		return TYPE_HXN;
-
 	bcdDevice = le16_to_cpu(desc->bcdDevice);
 	bcdUSB = le16_to_cpu(desc->bcdUSB);
 
 	switch (bcdDevice) {
+	case 0x100:
+		/*
+		 * Assume it's an HXN-type if the device doesn't support the old read
+		 * request value.
+		 */
+		if (bcdUSB == 0x200 && !pl2303_supports_hx_status(serial))
+			return TYPE_HXN;
+		break;
 	case 0x300:
 		if (bcdUSB == 0x200)
 			return TYPE_TA;