[PATCH v2] i2c: of: Try to find an I2C adapter matching the parent

[Thierry Reding <thierry.reding@gmail.com>]

From: Thierry Reding <treding@nvidia.com>

If an I2C adapter doesn't match the provided device tree node, also try
matching the parent's device tree node. This allows finding an adapter
based on the device node of the parent device that was used to register
it.

This fixes a regression on Tegra124-based Chromebooks (Nyan) where the
eDP controller registers an I2C adapter that is used to read to EDID.
After commit 993a815dcbb2 ("dt-bindings: panel: Add missing .txt
suffix") this stopped working because the I2C adapter could no longer
be found. The approach in this patch fixes the regression without
introducing the issues that the above commit solved.

Fixes: 17ab7806de0c ("drm: don't link DP aux i2c adapter to the hardware device node")
Signed-off-by: Thierry Reding <treding@nvidia.com>
---
Changes in v2:
- check for both device and parent device tree nodes for each device
  instead of looping through the list of devices twice

 drivers/i2c/i2c-core-of.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
index 6cb7ad608bcd..0f01cdba9d2c 100644
--- a/drivers/i2c/i2c-core-of.c
+++ b/drivers/i2c/i2c-core-of.c
@@ -121,6 +121,17 @@ static int of_dev_node_match(struct device *dev, void *data)
 	return dev->of_node == data;
 }
 
+static int of_dev_or_parent_node_match(struct device *dev, void *data)
+{
+	if (dev->of_node == data)
+		return 1;
+
+	if (dev->parent)
+		return dev->parent->of_node == data;
+
+	return 0;
+}
+
 /* must call put_device() when done with returned i2c_client device */
 struct i2c_client *of_find_i2c_device_by_node(struct device_node *node)
 {
@@ -145,7 +156,8 @@ struct i2c_adapter *of_find_i2c_adapter_by_node(struct device_node *node)
 	struct device *dev;
 	struct i2c_adapter *adapter;
 
-	dev = bus_find_device(&i2c_bus_type, NULL, node, of_dev_node_match);
+	dev = bus_find_device(&i2c_bus_type, NULL, node,
+			      of_dev_or_parent_node_match);
 	if (!dev)
 		return NULL;
 
-- 
2.19.1

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