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i2c/of: Automatically populate i2c mux busses from device tree data. 

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>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Tested-by: Lars-Peter Clausen <lars@metafoo.de>

[wsa: removed superfluous ret-variable and fixed a typo in a comment]
Signed-off-by: Wolfram Sang <w.sang@pengutronix.de>
This commit is contained in:
David Daney 2012-04-12 14:14:23 -07:00 committed by Wolfram Sang
parent 5a3ecd5f98
commit bc45449b14
2 changed files with 83 additions and 0 deletions
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60
Documentation/devicetree/bindings/i2c/mux.txt Normal file
View File

@ -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;
};
};
};

23
drivers/i2c/i2c-mux.c
View File

@ -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 +127,25 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
priv->adap.algo_data = priv;
priv->adap.dev.parent = &parent->dev;
/*
* Try to populate the mux adapter's of_node, expands to
* nothing if !CONFIG_OF.
*/
if (mux_dev->of_node) {
struct device_node *child;
u32 reg;
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 +163,8 @@ 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);