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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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