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. Signed-off-by: Daniel Mack <[email protected]>
holoplot · Nov 8, 2023 · efa9074 · efa9074
1 parent dee4a4c
commit efa9074
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
@@ -1189,9 +1189,11 @@ 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");