i2c: core: fix lockdep warning for sparsely nested adapter chain

When adapters are chained in a sparse manner (with intermediate MFD devices,
for instance) the code currently fails to use the correct subclass for
the adapter's bus_lock which leads to false-positive lockdep warnings.

Fix this by walking the entire pedigree of the device and count all
adapters along the way instead of just checking the immediate parent.

Signed-off-by: Daniel Mack <daniel@zonque.org>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 7f30bcceebaed3380ce0b3325e5e48ca0dba8807..eac90a3cf61a4b7740108974ab114105cb74ae70 100644 (file)
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1194,9 +1194,11 @@ static void i2c_adapter_dev_release(struct device *dev)
 unsigned int i2c_adapter_depth(struct i2c_adapter *adapter)
 {
        unsigned int depth = 0;
+       struct device *parent;
 
-       while ((adapter = i2c_parent_is_i2c_adapter(adapter)))
-               depth++;
+       for (parent = adapter->dev.parent; parent; parent = parent->parent)
+               if (parent->type == &i2c_adapter_type)
+                       depth++;
 
        WARN_ONCE(depth >= MAX_LOCKDEP_SUBCLASSES,
                  "adapter depth exceeds lockdep subclass limit\n");