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>

diff --git a/drivers/usb/serial/cypress_m8.c b/drivers/usb/serial/cypress_m8.c
index c42d3bd..f0c5d2a 100644 (file)
--- 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 */