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Subject[PATCH v3 2/2] i2c/of: Automatically populate i2c mux busses from device tree data.
Date
From: David Daney <david.daney@cavium.com>

For 'normal' i2c bus drivers, we can call of_i2c_register_devices()
and have the device tree framework automatically populate the bus with
the devices specified in the device tree.

This patch adds a common code to the i2c mux framework to have the mux
sub-busses be populated by the of_i2c_register_devices() too. If the
mux device has an of_node, we populate the sub-bus' of_node so that
the subsequent call to of_i2c_register_devices() will find the
corresponding devices.

It seemed better to put this logic in i2c_add_mux_adapter() rather
than the individual mux drivers, as they will all probably want to do
the same thing.

Signed-off-by: David Daney <david.daney@cavium.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>
---
Documentation/devicetree/bindings/i2c/mux.txt | 60 +++++++++++++++++++++++++
drivers/i2c/i2c-mux.c | 24 ++++++++++
2 files changed, 84 insertions(+), 0 deletions(-)
create mode 100644 Documentation/devicetree/bindings/i2c/mux.txt
diff --git a/Documentation/devicetree/bindings/i2c/mux.txt b/Documentation/devicetree/bindings/i2c/mux.txt
new file mode 100644
index 0000000..af84cce
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/mux.txt
@@ -0,0 +1,60 @@
+Common i2c bus multiplexer/switch properties.
+
+An i2c bus multiplexer/switch will have several child busses that are
+numbered uniquely in a device dependent manner. The nodes for an i2c bus
+multiplexer/switch will have one child node for each child
+bus.
+
+Required properties:
+- #address-cells = <1>;
+- #size-cells = <0>;
+
+Required properties for child nodes:
+- #address-cells = <1>;
+- #size-cells = <0>;
+- reg : The sub-bus number.
+
+Optional properties for child nodes:
+- Other properties specific to the multiplexer/switch hardware.
+- Child nodes conforming to i2c bus binding
+
+
+Example :
+
+ /*
+ An NXP pca9548 8 channel I2C multiplexer at address 0x70
+ with two NXP pca8574 GPIO expanders attached, one each to
+ ports 3 and 4.
+ */
+
+ mux@70 {
+ compatible = "nxp,pca9548";
+ reg = <0x70>;
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ i2c@3 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reg = <3>;
+
+ gpio1: gpio@38 {
+ compatible = "nxp,pca8574";
+ reg = <0x38>;
+ #gpio-cells = <2>;
+ gpio-controller;
+ };
+ };
+ i2c@4 {
+ #address-cells = <1>;
+ #size-cells = <0>;
+ reg = <4>;
+
+ gpio2: gpio@38 {
+ compatible = "nxp,pca8574";
+ reg = <0x38>;
+ #gpio-cells = <2>;
+ gpio-controller;
+ };
+ };
+ };
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 26ab31d..609794b 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -24,6 +24,8 @@
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
+#include <linux/of.h>
+#include <linux/of_i2c.h>

/* multiplexer per channel data */
struct i2c_mux_priv {
@@ -125,6 +127,26 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
priv->adap.algo_data = priv;
priv->adap.dev.parent = &parent->dev;

+ /*
+ * Try to get populate the mux adapter's of_node, expands to
+ * nothing if !CONFIG_OF.
+ */
+ if (mux_dev->of_node) {
+ struct device_node *child;
+ u32 reg;
+ int ret;
+
+ for_each_child_of_node(mux_dev->of_node, child) {
+ ret = of_property_read_u32(child, "reg", &reg);
+ if (ret)
+ continue;
+ if (chan_id == reg) {
+ priv->adap.dev.of_node = child;
+ break;
+ }
+ }
+ }
+
if (force_nr) {
priv->adap.nr = force_nr;
ret = i2c_add_numbered_adapter(&priv->adap);
@@ -142,6 +164,8 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
i2c_adapter_id(&priv->adap));

+ of_i2c_register_devices(&priv->adap);
+
return &priv->adap;
}
EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
--
1.7.2.3


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