USB: mos7840: fix device-type detection

Fix race in device-type detection introduced by commit 0eafe4de ("USB:
serial: mos7840: add support for MCS7810 devices") which used a static
variable to hold the device type.

Move type detection to probe and use serial data to store the device
type.

Cc: stable@vger.kernel.org
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 35 insertions, 40 deletions

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 73dda1cc8028..e95d91434785 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -187,8 +187,6 @@ enum mos7840_flag {
         MOS7840_FLAG_CTRL_BUSY,
 };
 
-static int device_type;
-
 static const struct usb_device_id id_table[] = {
         {USB_DEVICE(USB_VENDOR_ID_MOSCHIP, MOSCHIP_DEVICE_ID_7840)},
         {USB_DEVICE(USB_VENDOR_ID_MOSCHIP, MOSCHIP_DEVICE_ID_7820)},
@@ -830,18 +828,6 @@ static void mos7840_bulk_out_data_callback(struct urb *urb)
 /************************************************************************/
 /*       D R I V E R  T T Y  I N T E R F A C E  F U N C T I O N S       */
 /************************************************************************/
-#ifdef MCSSerialProbe
-static int mos7840_serial_probe(struct usb_serial *serial,
-                                const struct usb_device_id *id)
-{
-
-        /*need to implement the mode_reg reading and updating\
-           structures usb_serial_ device_type\
-           (i.e num_ports, num_bulkin,bulkout etc) */
-        /* Also we can update the changes  attach */
-        return 1;
-}
-#endif
 
 /*****************************************************************************
  * mos7840_open
@@ -2201,38 +2187,48 @@ static int mos7810_check(struct usb_serial *serial)
         return 0;
 }
 
-static int mos7840_calc_num_ports(struct usb_serial *serial)
+static int mos7840_probe(struct usb_serial *serial,
+                                const struct usb_device_id *id)
 {
-        __u16 data = 0x00;
+        u16 product = serial->dev->descriptor.idProduct;
         u8 *buf;
-        int mos7840_num_ports;
+        int device_type;
+
+        if (product == MOSCHIP_DEVICE_ID_7810 ||
+                product == MOSCHIP_DEVICE_ID_7820) {
+                device_type = product;
+                goto out;
+        }
 
         buf = kzalloc(VENDOR_READ_LENGTH, GFP_KERNEL);
-        if (buf) {
-                usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
+        if (!buf)
+                return -ENOMEM;
+
+        usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0),
                         MCS_RDREQ, MCS_RD_RTYPE, 0, GPIO_REGISTER, buf,
                         VENDOR_READ_LENGTH, MOS_WDR_TIMEOUT);
-                data = *buf;
-                kfree(buf);
-        }
 
-        if (serial->dev->descriptor.idProduct == MOSCHIP_DEVICE_ID_7810 ||
-                serial->dev->descriptor.idProduct == MOSCHIP_DEVICE_ID_7820) {
-                device_type = serial->dev->descriptor.idProduct;
-        } else {
-                /* For a MCS7840 device GPIO0 must be set to 1 */
-                if ((data & 0x01) == 1)
-                        device_type = MOSCHIP_DEVICE_ID_7840;
-                else if (mos7810_check(serial))
-                        device_type = MOSCHIP_DEVICE_ID_7810;
-                else
-                        device_type = MOSCHIP_DEVICE_ID_7820;
-        }
+        /* For a MCS7840 device GPIO0 must be set to 1 */
+        if (buf[0] & 0x01)
+                device_type = MOSCHIP_DEVICE_ID_7840;
+        else if (mos7810_check(serial))
+                device_type = MOSCHIP_DEVICE_ID_7810;
+        else
+                device_type = MOSCHIP_DEVICE_ID_7820;
+
+        kfree(buf);
+out:
+        usb_set_serial_data(serial, (void *)device_type);
+
+        return 0;
+}
+
+static int mos7840_calc_num_ports(struct usb_serial *serial)
+{
+        int device_type = (int)usb_get_serial_data(serial);
+        int mos7840_num_ports;
 
         mos7840_num_ports = (device_type >> 4) & 0x000F;
-        serial->num_bulk_in = mos7840_num_ports;
-        serial->num_bulk_out = mos7840_num_ports;
-        serial->num_ports = mos7840_num_ports;
 
         return mos7840_num_ports;
 }
@@ -2240,6 +2236,7 @@ static int mos7840_calc_num_ports(struct usb_serial *serial)
 static int mos7840_port_probe(struct usb_serial_port *port)
 {
         struct usb_serial *serial = port->serial;
+        int device_type = (int)usb_get_serial_data(serial);
         struct moschip_port *mos7840_port;
         int status;
         int pnum;
@@ -2496,9 +2493,7 @@ static struct usb_serial_driver moschip7840_4port_device = {
         .throttle = mos7840_throttle,
         .unthrottle = mos7840_unthrottle,
         .calc_num_ports = mos7840_calc_num_ports,
-#ifdef MCSSerialProbe
-        .probe = mos7840_serial_probe,
-#endif
+        .probe = mos7840_probe,
         .ioctl = mos7840_ioctl,
         .set_termios = mos7840_set_termios,
         .break_ctl = mos7840_break,