i2c: Add support for nested i2c bus locking

This patch adds the 'level' field into the i2c_adapter structure, which is 
used to represent the 'logical' level of nesting for the purposes of 
lockdep. This field is then used in the i2c_transfer() function, to 
acquire the per-adapter bus_lock with correct nesting level.

Signed-off-by: Jiri Kosina <jikos@jikos.cz>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

2 files changed, 2 insertions, 1 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 7ca81f42d14b..79eaa12474dd 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -603,7 +603,7 @@ int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
                 }
 #endif
 
-                mutex_lock(&adap->bus_lock);
+                mutex_lock_nested(&adap->bus_lock, adap->level);
                 ret = adap->algo->master_xfer(adap,msgs,num);
                 mutex_unlock(&adap->bus_lock);
 
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 9b5d04768c2c..08df4169b411 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -216,6 +216,7 @@ struct i2c_adapter {
         int (*client_unregister)(struct i2c_client *);
 
         /* data fields that are valid for all devices   */
+        u8 level;                       /* nesting level for lockdep */
         struct mutex bus_lock;
         struct mutex clist_lock;