Commit bc45449b authored by David Daney's avatar David Daney Committed by Wolfram Sang
Browse files

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: default avatarDavid Daney <david.daney@cavium.com>
Acked-by: default avatarStephen Warren <swarren@wwwdotorg.org>
Tested-by: default avatarLars-Peter Clausen <lars@metafoo.de>

[wsa: removed superfluous ret-variable and fixed a typo in a comment]
Signed-off-by: default avatarWolfram Sang <w.sang@pengutronix.de>
parent 5a3ecd5f

Documentation/devicetree/bindings/i2c/mux.txt

0 → 100644
+60 −0
Original line number Diff line number Diff line 
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;

			};

		};

	};

drivers/i2c/i2c-mux.c

+23 −0
Original line number Diff line number Diff line
@@ -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);

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