[RFC PATCH] i2c: skip of_i2c_register_device() for invalid child nodes

[Abhinav Kumar]

of_i2c_register_devices() adds all child nodes of a given i2c bus
however in certain device trees of_alias_from_compatible() and
of_property_read_u32() can fail as the child nodes of the device
might not be valid i2c client devices. One such example is the
i2c aux device for the DRM MST toplogy manager which uses the
display controller device node to add the i2c adaptor [1] leading
to an error spam like below

i2c i2c-20: of_i2c: register /soc at 0/display-subsystem at ae00000/display-controller at ae01000/ports
i2c i2c-20: of_i2c: modalias failure on /soc at 0/display-subsystem at ae00000/display-controller at ae01000/ports
i2c i2c-20: Failed to create I2C device for /soc at 0/display-subsystem at ae00000/display-controller at ae01000/ports
i2c i2c-20: of_i2c: register /soc at 0/display-subsystem at ae00000/display-controller at ae01000/opp-table
i2c i2c-20: of_i2c: invalid reg on /soc at 0/display-subsystem at ae00000/display-controller at ae01000/opp-table
i2c i2c-20: Failed to create I2C device for /soc at 0/display-subsystem at ae00000/display-controller at ae01000/opp-table

Add protection against invalid child nodes before trying to register
i2c devices for all child nodes.

[1] : https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/display/drm_dp_mst_topology.c#L5985

Signed-off-by: Abhinav Kumar <quic_abhinavk at quicinc.com>
---
 drivers/i2c/i2c-core-of.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/i2c/i2c-core-of.c b/drivers/i2c/i2c-core-of.c
index a6c407d36800..62a2603c3092 100644
--- a/drivers/i2c/i2c-core-of.c
+++ b/drivers/i2c/i2c-core-of.c
@@ -86,6 +86,8 @@ void of_i2c_register_devices(struct i2c_adapter *adap)
 {
 	struct device_node *bus, *node;
 	struct i2c_client *client;
+	u32 addr;
+	char temp[16];
 
 	/* Only register child devices if the adapter has a node pointer set */
 	if (!adap->dev.of_node)
@@ -101,6 +103,10 @@ void of_i2c_register_devices(struct i2c_adapter *adap)
 		if (of_node_test_and_set_flag(node, OF_POPULATED))
 			continue;
 
+		if (of_property_read_u32(node, "reg", &addr) ||
+		    of_alias_from_compatible(node, temp, sizeof(temp)))
+			continue;
+
 		client = of_i2c_register_device(adap, node);
 		if (IS_ERR(client)) {
 			dev_err(&adap->dev,
-- 
2.34.1