2 files changed, 14 insertions, 2 deletions

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)