Do not blindly use ftok() in snapscani_mutex_open(). Compute an IPC key based

on the product ID, bus number and device number for libusb devices; fallback
to ftok() otherwise and check the return value.

ChangeLog

@@ -1,3 +1,12 @@
+2008-03-28  Julien Blache <jb@jblache.org>
+	* sanei/sanei_usb.c, include/sane/sanei_usb.h: add
+	sanei_usb_get_vendor_product_byname().
+	* backend/snapscan-mutex.c: do not use ftok() in
+	snapscani_mutex_open(); ftok() will fail with anything for which
+	the devicename is not a filename. Construct an IPC key based on
+	the product ID, bus number and device number for libusb devices,
+	otherwise fallback to ftok() and check its return value.
+
 2008-03-28  m. allan noah <kitno455 a t gmail d o t com>
 	* backend/hp-scl.c: add usleep to improve usb performance, from
 	  jim a t meyering d o t net

backend/snapscan-mutex.c

@@ -118,13 +118,51 @@ static struct sembuf sem_signal = { 0, 1, 0 };
 
 static int snapscani_mutex_open(snapscan_mutex_t* sem_id, const char* dev)
 {
-    *sem_id = semget( ftok(dev,0x12), 1, IPC_CREAT | 0660 );
-    if (*sem_id != -1)
+    static const char *me = "snapscani_mutex_open";
+    key_t ipc_key;
+    int pid, devnum, busnum;
+
+    if (strstr(dev, "libusb:") == dev)
     {
-        semop(*sem_id, &sem_signal, 1);
-        return 1;
+        if (sanei_usb_get_vendor_product_byname(dev, NULL, &pid) != SANE_STATUS_GOOD)
+	{
+	    DBG (DL_MAJOR_ERROR, "%s: could not obtain USB product ID for device %s\n", me, dev);
+	    return 0;
+	}
+
+	if (sscanf(dev, "libusb:%d:%d", &busnum, &devnum) != 2)
+	{
+	    DBG (DL_MAJOR_ERROR, "%s: could not parse device string: %s\n", me, strerror(errno));
+	    return 0;
+	}
+
+	ipc_key = pid << 16;
+	ipc_key |= (busnum & 0xff) << 8;
+	ipc_key |= (devnum & 0xff);
+
+	DBG (DL_INFO, "%s: using IPC key 0x%08x for device %s (pid 0x%04x, bus 0x%02x, dev 0x%02x)\n",
+	     me, ipc_key, dev, pid, busnum, devnum);
     }
-    return 0;
+    else
+    {
+      ipc_key = ftok(dev, 0x12);
+
+	if (ipc_key == -1)
+	{
+	  DBG (DL_MAJOR_ERROR, "%s: could not obtain IPC key for device %s: %s\n", me, dev, strerror(errno));
+	    return 0;
+	}
+    }
+
+    *sem_id = semget( ipc_key, 1, IPC_CREAT | 0660 );
+    if (*sem_id == -1)
+    {
+        DBG (DL_MAJOR_ERROR, "%s: semget failed: %s\n", me, strerror(errno));
+	return 0;
+    }
+
+    semop(*sem_id, &sem_signal, 1);
+    return 1;
 }
 
 static void snapscani_mutex_close(snapscan_mutex_t* sem_id)

include/sane/sanei_usb.h

@@ -180,6 +180,22 @@ struct sanei_usb_dev_descriptor
  */
 extern void sanei_usb_init (void);
 
+/** Get the vendor and product ids by device name.
+ *
+ * @param devname 
+ * @param vendor vendor id
+ * @param product product id
+ *
+ * @return
+ * - SANE_STATUS_GOOD - if the ids could be determined
+ * - SANE_STATUS_INVAL - if the device is not found
+ * - SANE_STATUS_UNSUPPORTED - if this method is not supported with the current
+ *   access method
+ */
+SANE_Status
+sanei_usb_get_vendor_product_byname (SANE_String_Const devname,
+				     SANE_Word * vendor, SANE_Word * product);
+
 /** Get the vendor and product ids.
  *
  * Currently, only libusb devices and scanners supported by the Linux USB 

sanei/sanei_usb.c

@@ -646,6 +646,44 @@ sanei_usb_attach_matching_devices (const char *name,
     (*attach) (name);
 }
 
+SANE_Status
+sanei_usb_get_vendor_product_byname (SANE_String_Const devname,
+				     SANE_Word * vendor, SANE_Word * product)
+{
+  int devcount;
+  SANE_Bool found = SANE_FALSE;
+
+  for (devcount = 0; devcount < MAX_DEVICES && devices[devcount].devname != 0;
+       devcount++)
+    {
+      if (strcmp (devices[devcount].devname, devname) == 0)
+	{
+	  found = SANE_TRUE;
+	  break;
+	}
+    }
+
+  if (!found)
+    {
+      DBG (1, "sanei_usb_get_vendor_product_byname: can't find device `%s' in list\n", devname);
+      return SANE_STATUS_INVAL;
+    }
+
+  if ((devices[devcount].vendor == 0) && (devices[devcount].product == 0))
+    {
+      DBG (1, "sanei_usb_get_vendor_product_byname: not support for this method\n");
+      return SANE_STATUS_UNSUPPORTED;
+    }
+
+  if (vendor)
+    *vendor = devices[devcount].vendor;
+
+  if (product)
+    *product = devices[devcount].product;
+
+  return SANE_STATUS_GOOD;
+}
+
 SANE_Status
 sanei_usb_get_vendor_product (SANE_Int dn, SANE_Word * vendor,
 			      SANE_Word * product)