1 files changed, 25 insertions, 1 deletions

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 7360f9c37256..c21ae20ae362 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -182,6 +182,29 @@ static ssize_t i2cdev_write (struct file *file, const char __user *buf, size_t c
         return ret;
 }
 
+/* This address checking function differs from the one in i2c-core
+   in that it considers an address with a registered device, but no
+   bounded driver, as NOT busy. */
+static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
+{
+        struct list_head *item;
+        struct i2c_client *client;
+        int res = 0;
+
+        mutex_lock(&adapter->clist_lock);
+        list_for_each(item, &adapter->clients) {
+                client = list_entry(item, struct i2c_client, list);
+                if (client->addr == addr) {
+                        if (client->driver)
+                                res = -EBUSY;
+                        break;
+                }
+        }
+        mutex_unlock(&adapter->clist_lock);
+
+        return res;
+}
+
 static int i2cdev_ioctl(struct inode *inode, struct file *file,
                 unsigned int cmd, unsigned long arg)
 {
@@ -213,8 +236,9 @@ static int i2cdev_ioctl(struct inode *inode, struct file *file,
                 if ((arg > 0x3ff) ||
                     (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
                         return -EINVAL;
-                if ((cmd == I2C_SLAVE) && i2c_check_addr(client->adapter,arg))
+                if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
                         return -EBUSY;
+                /* REVISIT: address could become busy later */
                 client->addr = arg;
                 return 0;
         case I2C_TENBIT: