diff --git a/drivers/usb/class/cdc-acm.c b/drivers/usb/class/cdc-acm.c
index 9d6495424b06..077d58ac3dcb 100644
--- a/drivers/usb/class/cdc-acm.c
+++ b/drivers/usb/class/cdc-acm.c
@@ -148,8 +148,15 @@ static int acm_ctrl_msg(struct acm *acm, int request, int value,
 /* devices aren't required to support these requests.
  * the cdc acm descriptor tells whether they do...
  */
-#define acm_set_control(acm, control) \
-	acm_ctrl_msg(acm, USB_CDC_REQ_SET_CONTROL_LINE_STATE, control, NULL, 0)
+static inline int acm_set_control(struct acm *acm, int control)
+{
+	if (acm->quirks & QUIRK_CONTROL_LINE_STATE)
+		return -EOPNOTSUPP;
+
+	return acm_ctrl_msg(acm, USB_CDC_REQ_SET_CONTROL_LINE_STATE,
+			control, NULL, 0);
+}
+
 #define acm_set_line(acm, line) \
 	acm_ctrl_msg(acm, USB_CDC_REQ_SET_LINE_CODING, 0, line, sizeof *(line))
 #define acm_send_break(acm, ms) \
@@ -1320,6 +1327,7 @@ made_compressed_probe:
 	tty_port_init(&acm->port);
 	acm->port.ops = &acm_port_ops;
 	init_usb_anchor(&acm->delayed);
+	acm->quirks = quirks;
 
 	buf = usb_alloc_coherent(usb_dev, ctrlsize, GFP_KERNEL, &acm->ctrl_dma);
 	if (!buf) {
@@ -1687,6 +1695,8 @@ static const struct usb_device_id acm_ids[] = {
 	{ USB_DEVICE(0x0572, 0x1328), /* Shiro / Aztech USB MODEM UM-3100 */
 	.driver_info = NO_UNION_NORMAL, /* has no union descriptor */
 	},
+	{ USB_DEVICE(0x20df, 0x0001), /* Simtec Electronics Entropy Key */
+	.driver_info = QUIRK_CONTROL_LINE_STATE, },
 	{ USB_DEVICE(0x2184, 0x001c) },	/* GW Instek AFG-2225 */
 	{ USB_DEVICE(0x22b8, 0x6425), /* Motorola MOTOMAGX phones */
 	},
diff --git a/drivers/usb/class/cdc-acm.h b/drivers/usb/class/cdc-acm.h
index fc75651afe1c..d3251ebd09e2 100644
--- a/drivers/usb/class/cdc-acm.h
+++ b/drivers/usb/class/cdc-acm.h
@@ -121,6 +121,7 @@ struct acm {
 	unsigned int throttle_req:1;			/* throttle requested */
 	u8 bInterval;
 	struct usb_anchor delayed;			/* writes queued for a device about to be woken */
+	unsigned long quirks;
 };
 
 #define CDC_DATA_INTERFACE_TYPE	0x0a
@@ -132,3 +133,4 @@ struct acm {
 #define NOT_A_MODEM			BIT(3)
 #define NO_DATA_INTERFACE		BIT(4)
 #define IGNORE_DEVICE			BIT(5)
+#define QUIRK_CONTROL_LINE_STATE	BIT(6)