USB: cypress_m8: Don't issue GET_CONFIG for certain devices

Earthmate LT-20 devices (both "old" and "new" versions) can't tolerate
a GET_CONFIG command.  The original Earthmate has no trouble with
this.  Presumably other non-Earthmate devices are still OK as well.
This change disables the use of GET_CONFIG for cases where it is known
not to work.

Signed-off-by: Mike Isely <isely@pobox.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 19 insertions, 2 deletions

diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index c42d3bdbe98c..f0c5d2a7ab94 100644
--- a/drivers/usb/serial/cypress_m8.c
+++ b/drivers/usb/serial/cypress_m8.c
@@ -145,6 +145,7 @@ struct cypress_private {
         __u8 current_config;               /* stores the current configuration byte */
         __u8 rx_flags;                     /* throttling - used from whiteheat/ftdi_sio */
         enum packet_format pkt_fmt;        /* format to use for packet send / receive */
+        int get_cfg_unsafe;                /* If true, the CYPRESS_GET_CONFIG is unsafe */
         int baud_rate;                     /* stores current baud rate in integer form */
         int cbr_mask;                      /* stores current baud rate in masked form */
         int isthrottled;                   /* if throttled, discard reads */
@@ -401,6 +402,12 @@ static int cypress_serial_control (struct usb_serial_port *port, unsigned baud_m
                         }
                 break;
                 case CYPRESS_GET_CONFIG:
+                        if (priv->get_cfg_unsafe) {
+                                /* Not implemented for this device,
+                                   and if we try to do it we're likely
+                                   to crash the hardware. */
+                                return -ENOTTY;
+                        }
                         dbg("%s - retreiving serial line settings", __FUNCTION__);
                         /* set initial values in feature buffer */
                         memset(feature_buffer, 0, sizeof(feature_buffer));
@@ -570,20 +577,30 @@ static int generic_startup (struct usb_serial *serial)
 static int cypress_earthmate_startup (struct usb_serial *serial)
 {
         struct cypress_private *priv;
+        struct usb_serial_port *port = serial->port[0];
 
         dbg("%s", __FUNCTION__);
 
         if (generic_startup(serial)) {
                 dbg("%s - Failed setting up port %d", __FUNCTION__,
-                                serial->port[0]->number);
+                                port->number);
                 return 1;
         }
 
-        priv = usb_get_serial_port_data(serial->port[0]);
+        priv = usb_get_serial_port_data(port);
         priv->chiptype = CT_EARTHMATE;
         /* All Earthmate devices use the separated-count packet
            format!  Idiotic. */
         priv->pkt_fmt = packet_format_1;
+        if (serial->dev->descriptor.idProduct != PRODUCT_ID_EARTHMATEUSB) {
+                /* The old original USB Earthmate seemed able to
+                   handle GET_CONFIG requests; everything they've
+                   produced since that time crashes if this command is
+                   attempted :-( */
+                dbg("%s - Marking this device as unsafe for GET_CONFIG "
+                    "commands", __func__);
+                priv->get_cfg_unsafe = !0;
+        }
 
         return 0;
 } /* cypress_earthmate_startup */