Merge branch 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging

* 'i2c-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jdelvare/staging:
  i2c: I2C bus multiplexer driver pca954x
  i2c: Multiplexed I2C bus core support
  i2c: Use a separate mutex for userspace client lists
  i2c: Make i2c_default_probe self-sufficient
  i2c: Drop dummy variable
  i2c: Move adapter locking helpers to i2c-core
  V4L/DVB: Use custom I2C probing function mechanism
  i2c: Add support for custom probe function
  i2c-dev: Use memdup_user
  i2c-dev: Remove unnecessary kmalloc casts

8 files changed, 671 insertions, 61 deletions

diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig
index d06083fdffbb..30f06e956bfb 100644
--- a/drivers/i2c/Kconfig
+++ b/drivers/i2c/Kconfig
@@ -47,6 +47,19 @@ config I2C_CHARDEV
           This support is also available as a module.  If so, the module 
           will be called i2c-dev.
 
+config I2C_MUX
+        tristate "I2C bus multiplexing support"
+        depends on EXPERIMENTAL
+        help
+          Say Y here if you want the I2C core to support the ability to
+          handle multiplexed I2C bus topologies, by presenting each
+          multiplexed segment as a I2C adapter.
+
+          This support is also available as a module.  If so, the module
+          will be called i2c-mux.
+
+source drivers/i2c/muxes/Kconfig
+
 config I2C_HELPER_AUTO
         bool "Autoselect pertinent helper modules"
         default y
diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile
index a7d9b4be9bb3..c00fd66388f5 100644
--- a/drivers/i2c/Makefile
+++ b/drivers/i2c/Makefile
@@ -6,7 +6,8 @@ obj-$(CONFIG_I2C_BOARDINFO)	+= i2c-boardinfo.o
 obj-$(CONFIG_I2C)               += i2c-core.o
 obj-$(CONFIG_I2C_SMBUS)         += i2c-smbus.o
 obj-$(CONFIG_I2C_CHARDEV)       += i2c-dev.o
-obj-y                           += algos/ busses/
+obj-$(CONFIG_I2C_MUX)           += i2c-mux.o
+obj-y                           += algos/ busses/ muxes/
 
 ifeq ($(CONFIG_I2C_DEBUG_CORE),y)
 EXTRA_CFLAGS += -DDEBUG
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index df937df845eb..6649176de940 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -20,7 +20,9 @@
 /* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>.
    All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
    SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
-   Jean Delvare <khali@linux-fr.org> */
+   Jean Delvare <khali@linux-fr.org>
+   Mux support by Rodolfo Giometti <giometti@enneenne.com> and
+   Michael Lawnick <michael.lawnick.ext@nsn.com> */
 
 #include <linux/module.h>
 #include <linux/kernel.h>
@@ -423,11 +425,87 @@ static int __i2c_check_addr_busy(struct device *dev, void *addrp)
         return 0;
 }
 
+/* walk up mux tree */
+static int i2c_check_mux_parents(struct i2c_adapter *adapter, int addr)
+{
+        int result;
+
+        result = device_for_each_child(&adapter->dev, &addr,
+                                        __i2c_check_addr_busy);
+
+        if (!result && i2c_parent_is_i2c_adapter(adapter))
+                result = i2c_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        return result;
+}
+
+/* recurse down mux tree */
+static int i2c_check_mux_children(struct device *dev, void *addrp)
+{
+        int result;
+
+        if (dev->type == &i2c_adapter_type)
+                result = device_for_each_child(dev, addrp,
+                                                i2c_check_mux_children);
+        else
+                result = __i2c_check_addr_busy(dev, addrp);
+
+        return result;
+}
+
 static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
 {
-        return device_for_each_child(&adapter->dev, &addr,
-                                     __i2c_check_addr_busy);
+        int result = 0;
+
+        if (i2c_parent_is_i2c_adapter(adapter))
+                result = i2c_check_mux_parents(
+                                    to_i2c_adapter(adapter->dev.parent), addr);
+
+        if (!result)
+                result = device_for_each_child(&adapter->dev, &addr,
+                                                i2c_check_mux_children);
+
+        return result;
+}
+
+/**
+ * i2c_lock_adapter - Get exclusive access to an I2C bus segment
+ * @adapter: Target I2C bus segment
+ */
+void i2c_lock_adapter(struct i2c_adapter *adapter)
+{
+        if (i2c_parent_is_i2c_adapter(adapter))
+                i2c_lock_adapter(to_i2c_adapter(adapter->dev.parent));
+        else
+                rt_mutex_lock(&adapter->bus_lock);
+}
+EXPORT_SYMBOL_GPL(i2c_lock_adapter);
+
+/**
+ * i2c_trylock_adapter - Try to get exclusive access to an I2C bus segment
+ * @adapter: Target I2C bus segment
+ */
+static int i2c_trylock_adapter(struct i2c_adapter *adapter)
+{
+        if (i2c_parent_is_i2c_adapter(adapter))
+                return i2c_trylock_adapter(to_i2c_adapter(adapter->dev.parent));
+        else
+                return rt_mutex_trylock(&adapter->bus_lock);
+}
+
+/**
+ * i2c_unlock_adapter - Release exclusive access to an I2C bus segment
+ * @adapter: Target I2C bus segment
+ */
+void i2c_unlock_adapter(struct i2c_adapter *adapter)
+{
+        if (i2c_parent_is_i2c_adapter(adapter))
+                i2c_unlock_adapter(to_i2c_adapter(adapter->dev.parent));
+        else
+                rt_mutex_unlock(&adapter->bus_lock);
 }
+EXPORT_SYMBOL_GPL(i2c_unlock_adapter);
 
 /**
  * i2c_new_device - instantiate an i2c device
@@ -633,9 +711,9 @@ i2c_sysfs_new_device(struct device *dev, struct device_attribute *attr,
                 return -EINVAL;
 
         /* Keep track of the added device */
-        i2c_lock_adapter(adap);
+        mutex_lock(&adap->userspace_clients_lock);
         list_add_tail(&client->detected, &adap->userspace_clients);
-        i2c_unlock_adapter(adap);
+        mutex_unlock(&adap->userspace_clients_lock);
         dev_info(dev, "%s: Instantiated device %s at 0x%02hx\n", "new_device",
                  info.type, info.addr);
 
@@ -674,7 +752,7 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
 
         /* Make sure the device was added through sysfs */
         res = -ENOENT;
-        i2c_lock_adapter(adap);
+        mutex_lock(&adap->userspace_clients_lock);
         list_for_each_entry_safe(client, next, &adap->userspace_clients,
                                  detected) {
                 if (client->addr == addr) {
@@ -687,7 +765,7 @@ i2c_sysfs_delete_device(struct device *dev, struct device_attribute *attr,
                         break;
                 }
         }
-        i2c_unlock_adapter(adap);
+        mutex_unlock(&adap->userspace_clients_lock);
 
         if (res < 0)
                 dev_err(dev, "%s: Can't find device in list\n",
@@ -714,10 +792,11 @@ static const struct attribute_group *i2c_adapter_attr_groups[] = {
         NULL
 };
 
-static struct device_type i2c_adapter_type = {
+struct device_type i2c_adapter_type = {
         .groups         = i2c_adapter_attr_groups,
         .release        = i2c_adapter_dev_release,
 };
+EXPORT_SYMBOL_GPL(i2c_adapter_type);
 
 #ifdef CONFIG_I2C_COMPAT
 static struct class_compat *i2c_adapter_compat_class;
@@ -760,7 +839,7 @@ static int __process_new_adapter(struct device_driver *d, void *data)
 
 static int i2c_register_adapter(struct i2c_adapter *adap)
 {
-        int res = 0, dummy;
+        int res = 0;
 
         /* Can't register until after driver model init */
         if (unlikely(WARN_ON(!i2c_bus_type.p))) {
@@ -769,6 +848,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
         }
 
         rt_mutex_init(&adap->bus_lock);
+        mutex_init(&adap->userspace_clients_lock);
         INIT_LIST_HEAD(&adap->userspace_clients);
 
         /* Set default timeout to 1 second if not already set */
@@ -801,8 +881,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
 
         /* Notify drivers */
         mutex_lock(&core_lock);
-        dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
-                                 __process_new_adapter);
+        bus_for_each_drv(&i2c_bus_type, NULL, adap, __process_new_adapter);
         mutex_unlock(&core_lock);
 
         return 0;
@@ -975,7 +1054,7 @@ int i2c_del_adapter(struct i2c_adapter *adap)
                 return res;
 
         /* Remove devices instantiated from sysfs */
-        i2c_lock_adapter(adap);
+        mutex_lock(&adap->userspace_clients_lock);
         list_for_each_entry_safe(client, next, &adap->userspace_clients,
                                  detected) {
                 dev_dbg(&adap->dev, "Removing %s at 0x%x\n", client->name,
@@ -983,7 +1062,7 @@ int i2c_del_adapter(struct i2c_adapter *adap)
                 list_del(&client->detected);
                 i2c_unregister_device(client);
         }
-        i2c_unlock_adapter(adap);
+        mutex_unlock(&adap->userspace_clients_lock);
 
         /* Detach any active clients. This can't fail, thus we do not
            checking the returned value. */
@@ -1238,12 +1317,12 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 #endif
 
                 if (in_atomic() || irqs_disabled()) {
-                        ret = rt_mutex_trylock(&adap->bus_lock);
+                        ret = i2c_trylock_adapter(adap);
                         if (!ret)
                                 /* I2C activity is ongoing. */
                                 return -EAGAIN;
                 } else {
-                        rt_mutex_lock(&adap->bus_lock);
+                        i2c_lock_adapter(adap);
                 }
 
                 /* Retry automatically on arbitration loss */
@@ -1255,7 +1334,7 @@ int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
                         if (time_after(jiffies, orig_jiffies + adap->timeout))
                                 break;
                 }
-                rt_mutex_unlock(&adap->bus_lock);
+                i2c_unlock_adapter(adap);
 
                 return ret;
         } else {
@@ -1350,13 +1429,17 @@ static int i2c_default_probe(struct i2c_adapter *adap, unsigned short addr)
                                      I2C_SMBUS_BYTE_DATA, &dummy);
         else
 #endif
-        if ((addr & ~0x07) == 0x30 || (addr & ~0x0f) == 0x50
-         || !i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK))
-                err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
-                                     I2C_SMBUS_BYTE, &dummy);
-        else
+        if (!((addr & ~0x07) == 0x30 || (addr & ~0x0f) == 0x50)
+         && i2c_check_functionality(adap, I2C_FUNC_SMBUS_QUICK))
                 err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_WRITE, 0,
                                      I2C_SMBUS_QUICK, NULL);
+        else if (i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE))
+                err = i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
+                                     I2C_SMBUS_BYTE, &dummy);
+        else {
+                dev_warn(&adap->dev, "No suitable probing method supported\n");
+                err = -EOPNOTSUPP;
+        }
 
         return err >= 0;
 }
@@ -1437,16 +1520,6 @@ static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
         if (!(adapter->class & driver->class))
                 goto exit_free;
 
-        /* Stop here if the bus doesn't support probing */
-        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_READ_BYTE)) {
-                if (address_list[0] == I2C_CLIENT_END)
-                        goto exit_free;
-
-                dev_warn(&adapter->dev, "Probing not supported\n");
-                err = -EOPNOTSUPP;
-                goto exit_free;
-        }
-
         for (i = 0; address_list[i] != I2C_CLIENT_END; i += 1) {
                 dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
                         "addr 0x%02x\n", adap_id, address_list[i]);
@@ -1461,18 +1534,23 @@ static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
         return err;
 }
 
+int i2c_probe_func_quick_read(struct i2c_adapter *adap, unsigned short addr)
+{
+        return i2c_smbus_xfer(adap, addr, 0, I2C_SMBUS_READ, 0,
+                              I2C_SMBUS_QUICK, NULL) >= 0;
+}
+EXPORT_SYMBOL_GPL(i2c_probe_func_quick_read);
+
 struct i2c_client *
 i2c_new_probed_device(struct i2c_adapter *adap,
                       struct i2c_board_info *info,
-                      unsigned short const *addr_list)
+                      unsigned short const *addr_list,
+                      int (*probe)(struct i2c_adapter *, unsigned short addr))
 {
         int i;
 
-        /* Stop here if the bus doesn't support probing */
-        if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_READ_BYTE)) {
-                dev_err(&adap->dev, "Probing not supported\n");
-                return NULL;
-        }
+        if (!probe)
+                probe = i2c_default_probe;
 
         for (i = 0; addr_list[i] != I2C_CLIENT_END; i++) {
                 /* Check address validity */
@@ -1490,7 +1568,7 @@ i2c_new_probed_device(struct i2c_adapter *adap,
                 }
 
                 /* Test address responsiveness */
-                if (i2c_default_probe(adap, addr_list[i]))
+                if (probe(adap, addr_list[i]))
                         break;
         }
 
@@ -2002,7 +2080,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
         flags &= I2C_M_TEN | I2C_CLIENT_PEC;
 
         if (adapter->algo->smbus_xfer) {
-                rt_mutex_lock(&adapter->bus_lock);
+                i2c_lock_adapter(adapter);
 
                 /* Retry automatically on arbitration loss */
                 orig_jiffies = jiffies;
@@ -2016,7 +2094,7 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags,
                                        orig_jiffies + adapter->timeout))
                                 break;
                 }
-                rt_mutex_unlock(&adapter->bus_lock);
+                i2c_unlock_adapter(adapter);
         } else
                 res = i2c_smbus_xfer_emulated(adapter, addr, flags, read_write,
                                               command, protocol, data);
diff --git a/drivers/i2c/i2c-dev.c b/drivers/i2c/i2c-dev.c
index e0694e4d86c7..5f3a52d517c3 100644
--- a/drivers/i2c/i2c-dev.c
+++ b/drivers/i2c/i2c-dev.c
@@ -167,13 +167,9 @@ static ssize_t i2cdev_write(struct file *file, const char __user *buf,
         if (count > 8192)
                 count = 8192;
 
-        tmp = kmalloc(count, GFP_KERNEL);
-        if (tmp == NULL)
-                return -ENOMEM;
-        if (copy_from_user(tmp, buf, count)) {
-                kfree(tmp);
-                return -EFAULT;
-        }
+        tmp = memdup_user(buf, count);
+        if (IS_ERR(tmp))
+                return PTR_ERR(tmp);
 
         pr_debug("i2c-dev: i2c-%d writing %zu bytes.\n",
                 iminor(file->f_path.dentry->d_inode), count);
@@ -193,12 +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,
@@ -219,9 +253,7 @@ static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
         if (rdwr_arg.nmsgs > I2C_RDRW_IOCTL_MAX_MSGS)
                 return -EINVAL;
 
-        rdwr_pa = (struct i2c_msg *)
-                kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg),
-                GFP_KERNEL);
+        rdwr_pa = kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg), GFP_KERNEL);
         if (!rdwr_pa)
                 return -ENOMEM;
 
@@ -247,15 +279,9 @@ static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
                         break;
                 }
                 data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
-                rdwr_pa[i].buf = kmalloc(rdwr_pa[i].len, GFP_KERNEL);
-                if (rdwr_pa[i].buf == NULL) {
-                        res = -ENOMEM;
-                        break;
-                }
-                if (copy_from_user(rdwr_pa[i].buf, data_ptrs[i],
-                                   rdwr_pa[i].len)) {
-                                ++i; /* Needs to be kfreed too */
-                                res = -EFAULT;
+                rdwr_pa[i].buf = memdup_user(data_ptrs[i], rdwr_pa[i].len);
+                if (IS_ERR(rdwr_pa[i].buf)) {
+                        res = PTR_ERR(rdwr_pa[i].buf);
                         break;
                 }
         }
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
new file mode 100644
index 000000000000..d32a4843fc3a
--- /dev/null
+++ b/drivers/i2c/i2c-mux.c
@@ -0,0 +1,165 @@
+/*
+ * Multiplexed I2C bus driver.
+ *
+ * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
+ * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
+ * Copyright (c) 2009-2010 NSN GmbH & Co KG <michael.lawnick.ext@nsn.com>
+ *
+ * Simplifies access to complex multiplexed I2C bus topologies, by presenting
+ * each multiplexed bus segment as an additional I2C adapter.
+ * Supports multi-level mux'ing (mux behind a mux).
+ *
+ * Based on:
+ *      i2c-virt.c from Kumar Gala <galak@kernel.crashing.org>
+ *      i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc.
+ *      i2c-virtual.c from Brian Kuschak <bkuschak@yahoo.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+
+/* multiplexer per channel data */
+struct i2c_mux_priv {
+        struct i2c_adapter adap;
+        struct i2c_algorithm algo;
+
+        struct i2c_adapter *parent;
+        void *mux_dev;  /* the mux chip/device */
+        u32  chan_id;   /* the channel id */
+
+        int (*select)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
+        int (*deselect)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
+};
+
+static int i2c_mux_master_xfer(struct i2c_adapter *adap,
+                               struct i2c_msg msgs[], int num)
+{
+        struct i2c_mux_priv *priv = adap->algo_data;
+        struct i2c_adapter *parent = priv->parent;
+        int ret;
+
+        /* Switch to the right mux port and perform the transfer. */
+
+        ret = priv->select(parent, priv->mux_dev, priv->chan_id);
+        if (ret >= 0)
+                ret = parent->algo->master_xfer(parent, msgs, num);
+        if (priv->deselect)
+                priv->deselect(parent, priv->mux_dev, priv->chan_id);
+
+        return ret;
+}
+
+static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
+                              u16 addr, unsigned short flags,
+                              char read_write, u8 command,
+                              int size, union i2c_smbus_data *data)
+{
+        struct i2c_mux_priv *priv = adap->algo_data;
+        struct i2c_adapter *parent = priv->parent;
+        int ret;
+
+        /* Select the right mux port and perform the transfer. */
+
+        ret = priv->select(parent, priv->mux_dev, priv->chan_id);
+        if (ret >= 0)
+                ret = parent->algo->smbus_xfer(parent, addr, flags,
+                                        read_write, command, size, data);
+        if (priv->deselect)
+                priv->deselect(parent, priv->mux_dev, priv->chan_id);
+
+        return ret;
+}
+
+/* Return the parent's functionality */
+static u32 i2c_mux_functionality(struct i2c_adapter *adap)
+{
+        struct i2c_mux_priv *priv = adap->algo_data;
+        struct i2c_adapter *parent = priv->parent;
+
+        return parent->algo->functionality(parent);
+}
+
+struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
+                                void *mux_dev, u32 force_nr, u32 chan_id,
+                                int (*select) (struct i2c_adapter *,
+                                               void *, u32),
+                                int (*deselect) (struct i2c_adapter *,
+                                                 void *, u32))
+{
+        struct i2c_mux_priv *priv;
+        int ret;
+
+        priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
+        if (!priv)
+                return NULL;
+
+        /* Set up private adapter data */
+        priv->parent = parent;
+        priv->mux_dev = mux_dev;
+        priv->chan_id = chan_id;
+        priv->select = select;
+        priv->deselect = deselect;
+
+        /* Need to do algo dynamically because we don't know ahead
+         * of time what sort of physical adapter we'll be dealing with.
+         */
+        if (parent->algo->master_xfer)
+                priv->algo.master_xfer = i2c_mux_master_xfer;
+        if (parent->algo->smbus_xfer)
+                priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
+        priv->algo.functionality = i2c_mux_functionality;
+
+        /* Now fill out new adapter structure */
+        snprintf(priv->adap.name, sizeof(priv->adap.name),
+                 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
+        priv->adap.owner = THIS_MODULE;
+        priv->adap.id = parent->id;
+        priv->adap.algo = &priv->algo;
+        priv->adap.algo_data = priv;
+        priv->adap.dev.parent = &parent->dev;
+
+        if (force_nr) {
+                priv->adap.nr = force_nr;
+                ret = i2c_add_numbered_adapter(&priv->adap);
+        } else {
+                ret = i2c_add_adapter(&priv->adap);
+        }
+        if (ret < 0) {
+                dev_err(&parent->dev,
+                        "failed to add mux-adapter (error=%d)\n",
+                        ret);
+                kfree(priv);
+                return NULL;
+        }
+
+        dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
+                 i2c_adapter_id(&priv->adap));
+
+        return &priv->adap;
+}
+EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
+
+int i2c_del_mux_adapter(struct i2c_adapter *adap)
+{
+        struct i2c_mux_priv *priv = adap->algo_data;
+        int ret;
+
+        ret = i2c_del_adapter(adap);
+        if (ret < 0)
+                return ret;
+        kfree(priv);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
+MODULE_LICENSE("GPL v2");
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
new file mode 100644
index 000000000000..4c9a99c4fcb0
--- /dev/null
+++ b/drivers/i2c/muxes/Kconfig
@@ -0,0 +1,18 @@
+#
+# Multiplexer I2C chip drivers configuration
+#
+
+menu "Multiplexer I2C Chip support"
+        depends on I2C_MUX
+
+config I2C_MUX_PCA954x
+        tristate "Philips PCA954x I2C Mux/switches"
+        depends on EXPERIMENTAL
+        help
+          If you say yes here you get support for the Philips PCA954x
+          I2C mux/switch devices.
+
+          This driver can also be built as a module.  If so, the module
+          will be called pca954x.
+
+endmenu
diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile
new file mode 100644
index 000000000000..bd83b5274815
--- /dev/null
+++ b/drivers/i2c/muxes/Makefile
@@ -0,0 +1,8 @@
+#
+# Makefile for multiplexer I2C chip drivers.
+
+obj-$(CONFIG_I2C_MUX_PCA954x)   += pca954x.o
+
+ifeq ($(CONFIG_I2C_DEBUG_BUS),y)
+EXTRA_CFLAGS += -DDEBUG
+endif
diff --git a/drivers/i2c/muxes/pca954x.c b/drivers/i2c/muxes/pca954x.c
new file mode 100644
index 000000000000..6f9accf3189d
--- /dev/null
+++ b/drivers/i2c/muxes/pca954x.c
@@ -0,0 +1,301 @@
+/*
+ * I2C multiplexer
+ *
+ * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
+ * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
+ *
+ * This module supports the PCA954x series of I2C multiplexer/switch chips
+ * made by Philips Semiconductors.
+ * This includes the:
+ *       PCA9540, PCA9542, PCA9543, PCA9544, PCA9545, PCA9546, PCA9547
+ *       and PCA9548.
+ *
+ * These chips are all controlled via the I2C bus itself, and all have a
+ * single 8-bit register. The upstream "parent" bus fans out to two,
+ * four, or eight downstream busses or channels; which of these
+ * are selected is determined by the chip type and register contents. A
+ * mux can select only one sub-bus at a time; a switch can select any
+ * combination simultaneously.
+ *
+ * Based on:
+ *      pca954x.c from Kumar Gala <galak@kernel.crashing.org>
+ * Copyright (C) 2006
+ *
+ * Based on:
+ *      pca954x.c from Ken Harrenstien
+ * Copyright (C) 2004 Google, Inc. (Ken Harrenstien)
+ *
+ * Based on:
+ *      i2c-virtual_cb.c from Brian Kuschak <bkuschak@yahoo.com>
+ * and
+ *      pca9540.c from Jean Delvare <khali@linux-fr.org>.
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/i2c.h>
+#include <linux/i2c-mux.h>
+
+#include <linux/i2c/pca954x.h>
+
+#define PCA954X_MAX_NCHANS 8
+
+enum pca_type {
+        pca_9540,
+        pca_9542,
+        pca_9543,
+        pca_9544,
+        pca_9545,
+        pca_9546,
+        pca_9547,
+        pca_9548,
+};
+
+struct pca954x {
+        enum pca_type type;
+        struct i2c_adapter *virt_adaps[PCA954X_MAX_NCHANS];
+
+        u8 last_chan;           /* last register value */
+};
+
+struct chip_desc {
+        u8 nchans;
+        u8 enable;      /* used for muxes only */
+        enum muxtype {
+                pca954x_ismux = 0,
+                pca954x_isswi
+        } muxtype;
+};
+
+/* Provide specs for the PCA954x types we know about */
+static const struct chip_desc chips[] = {
+        [pca_9540] = {
+                .nchans = 2,
+                .enable = 0x4,
+                .muxtype = pca954x_ismux,
+        },
+        [pca_9543] = {
+                .nchans = 2,
+                .muxtype = pca954x_isswi,
+        },
+        [pca_9544] = {
+                .nchans = 4,
+                .enable = 0x4,
+                .muxtype = pca954x_ismux,
+        },
+        [pca_9545] = {
+                .nchans = 4,
+                .muxtype = pca954x_isswi,
+        },
+        [pca_9547] = {
+                .nchans = 8,
+                .enable = 0x8,
+                .muxtype = pca954x_ismux,
+        },
+        [pca_9548] = {
+                .nchans = 8,
+                .muxtype = pca954x_isswi,
+        },
+};
+
+static const struct i2c_device_id pca954x_id[] = {
+        { "pca9540", pca_9540 },
+        { "pca9542", pca_9540 },
+        { "pca9543", pca_9543 },
+        { "pca9544", pca_9544 },
+        { "pca9545", pca_9545 },
+        { "pca9546", pca_9545 },
+        { "pca9547", pca_9547 },
+        { "pca9548", pca_9548 },
+        { }
+};
+MODULE_DEVICE_TABLE(i2c, pca954x_id);
+
+/* Write to mux register. Don't use i2c_transfer()/i2c_smbus_xfer()
+   for this as they will try to lock adapter a second time */
+static int pca954x_reg_write(struct i2c_adapter *adap,
+                             struct i2c_client *client, u8 val)
+{
+        int ret = -ENODEV;
+
+        if (adap->algo->master_xfer) {
+                struct i2c_msg msg;
+                char buf[1];
+
+                msg.addr = client->addr;
+                msg.flags = 0;
+                msg.len = 1;
+                buf[0] = val;
+                msg.buf = buf;
+                ret = adap->algo->master_xfer(adap, &msg, 1);
+        } else {
+                union i2c_smbus_data data;
+                ret = adap->algo->smbus_xfer(adap, client->addr,
+                                             client->flags,
+                                             I2C_SMBUS_WRITE,
+                                             val, I2C_SMBUS_BYTE, &data);
+        }
+
+        return ret;
+}
+
+static int pca954x_select_chan(struct i2c_adapter *adap,
+                               void *client, u32 chan)
+{
+        struct pca954x *data = i2c_get_clientdata(client);
+        const struct chip_desc *chip = &chips[data->type];
+        u8 regval;
+        int ret = 0;
+
+        /* we make switches look like muxes, not sure how to be smarter */
+        if (chip->muxtype == pca954x_ismux)
+                regval = chan | chip->enable;
+        else
+                regval = 1 << chan;
+
+        /* Only select the channel if its different from the last channel */
+        if (data->last_chan != regval) {
+                ret = pca954x_reg_write(adap, client, regval);
+                data->last_chan = regval;
+        }
+
+        return ret;
+}
+
+static int pca954x_deselect_mux(struct i2c_adapter *adap,
+                                void *client, u32 chan)
+{
+        struct pca954x *data = i2c_get_clientdata(client);
+
+        /* Deselect active channel */
+        data->last_chan = 0;
+        return pca954x_reg_write(adap, client, data->last_chan);
+}
+
+/*
+ * I2C init/probing/exit functions
+ */
+static int __devinit pca954x_probe(struct i2c_client *client,
+                                   const struct i2c_device_id *id)
+{
+        struct i2c_adapter *adap = to_i2c_adapter(client->dev.parent);
+        struct pca954x_platform_data *pdata = client->dev.platform_data;
+        int num, force;
+        struct pca954x *data;
+        int ret = -ENODEV;
+
+        if (!i2c_check_functionality(adap, I2C_FUNC_SMBUS_BYTE))
+                goto err;
+
+        data = kzalloc(sizeof(struct pca954x), GFP_KERNEL);
+        if (!data) {
+                ret = -ENOMEM;
+                goto err;
+        }
+
+        i2c_set_clientdata(client, data);
+
+        /* Read the mux register at addr to verify
+         * that the mux is in fact present.
+         */
+        if (i2c_smbus_read_byte(client) < 0) {
+                dev_warn(&client->dev, "probe failed\n");
+                goto exit_free;
+        }
+
+        data->type = id->driver_data;
+        data->last_chan = 0;               /* force the first selection */
+
+        /* Now create an adapter for each channel */
+        for (num = 0; num < chips[data->type].nchans; num++) {
+                force = 0;                        /* dynamic adap number */
+                if (pdata) {
+                        if (num < pdata->num_modes)
+                                /* force static number */
+                                force = pdata->modes[num].adap_id;
+                        else
+                                /* discard unconfigured channels */
+                                break;
+                }
+
+                data->virt_adaps[num] =
+                        i2c_add_mux_adapter(adap, client,
+                                force, num, pca954x_select_chan,
+                                (pdata && pdata->modes[num].deselect_on_exit)
+                                        ? pca954x_deselect_mux : NULL);
+
+                if (data->virt_adaps[num] == NULL) {
+                        ret = -ENODEV;
+                        dev_err(&client->dev,
+                                "failed to register multiplexed adapter"
+                                " %d as bus %d\n", num, force);
+                        goto virt_reg_failed;
+                }
+        }
+
+        dev_info(&client->dev,
+                 "registered %d multiplexed busses for I2C %s %s\n",
+                 num, chips[data->type].muxtype == pca954x_ismux
+                                ? "mux" : "switch", client->name);
+
+        return 0;
+
+virt_reg_failed:
+        for (num--; num >= 0; num--)
+                i2c_del_mux_adapter(data->virt_adaps[num]);
+exit_free:
+        kfree(data);
+err:
+        return ret;
+}
+
+static int __devexit pca954x_remove(struct i2c_client *client)
+{
+        struct pca954x *data = i2c_get_clientdata(client);
+        const struct chip_desc *chip = &chips[data->type];
+        int i, err;
+
+        for (i = 0; i < chip->nchans; ++i)
+                if (data->virt_adaps[i]) {
+                        err = i2c_del_mux_adapter(data->virt_adaps[i]);
+                        if (err)
+                                return err;
+                        data->virt_adaps[i] = NULL;
+                }
+
+        kfree(data);
+        return 0;
+}
+
+static struct i2c_driver pca954x_driver = {
+        .driver         = {
+                .name   = "pca954x",
+                .owner  = THIS_MODULE,
+        },
+        .probe          = pca954x_probe,
+        .remove         = __devexit_p(pca954x_remove),
+        .id_table       = pca954x_id,
+};
+
+static int __init pca954x_init(void)
+{
+        return i2c_add_driver(&pca954x_driver);
+}
+
+static void __exit pca954x_exit(void)
+{
+        i2c_del_driver(&pca954x_driver);
+}
+
+module_init(pca954x_init);
+module_exit(pca954x_exit);
+
+MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
+MODULE_DESCRIPTION("PCA954x I2C mux/switch driver");
+MODULE_LICENSE("GPL v2");