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

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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>
This commit is contained in:
Daniel Mack 2023-10-18 11:46:13 +02:00 committed by Wolfram Sang
parent 702c0dd7bc
commit 53801d2e76
1 changed files with 4 additions and 2 deletions
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6
drivers/i2c/i2c-core-base.c
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@ -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");