i2c: Multiplexed I2C bus core support

Add multiplexed bus core support. I2C multiplexer and switches
like pca954x get instantiated as new adapters per port.

Signed-off-by: Michael Lawnick <ml.lawnick@gmx.de>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 39 insertions, 1 deletions

diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index 0b0427f7d348..5f3a52d517c3 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -189,12 +189,50 @@ static int i2cdev_check(struct device *dev, void *addrp)
         return dev->driver ? -EBUSY : 0;
 }
 
+/* walk up mux tree */
+static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
+{
+        int result;
+
+        result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
+
+        if (!result && i2c_parent_is_i2c_adapter(adapter))
+                result = i2cdev_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        return result;
+}
+
+/* recurse down mux tree */
+static int i2cdev_check_mux_children(struct device *dev, void *addrp)
+{
+        int result;
+
+        if (dev->type == &i2c_adapter_type)
+                result = device_for_each_child(dev, addrp,
+                                                i2cdev_check_mux_children);
+        else
+                result = i2cdev_check(dev, addrp);
+
+        return result;
+}
+
 /* This address checking function differs from the one in i2c-core
    in that it considers an address with a registered device, but no
    driver bound to it, as NOT busy. */
 static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
 {
-        return device_for_each_child(&adapter->dev, &addr, i2cdev_check);
+        int result = 0;
+
+        if (i2c_parent_is_i2c_adapter(adapter))
+                result = i2cdev_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        if (!result)
+                result = device_for_each_child(&adapter->dev, &addr,
+                                                i2cdev_check_mux_children);
+
+        return result;
 }
 
 static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,