/*
 * 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/acpi.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/slab.h>
#include <linux/sysfs.h>

/* multiplexer per channel data */
struct i2c_mux_priv {
        struct i2c_adapter adap;
        struct i2c_algorithm algo;
        struct i2c_mux_core *muxc;
        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_mux_core *muxc = priv->muxc;
        struct i2c_adapter *parent = muxc->parent;
        int ret;

        /* Switch to the right mux port and perform the transfer. */

        ret = muxc->select(muxc, priv->chan_id);
        if (ret >= 0)
                ret = __i2c_transfer(parent, msgs, num);
        if (muxc->deselect)
                muxc->deselect(muxc, priv->chan_id);

        return ret;
}

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_mux_core *muxc = priv->muxc;
        struct i2c_adapter *parent = muxc->parent;
        int ret;

        /* Switch to the right mux port and perform the transfer. */

        ret = muxc->select(muxc, priv->chan_id);
        if (ret >= 0)
                ret = i2c_transfer(parent, msgs, num);
        if (muxc->deselect)
                muxc->deselect(muxc, 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_mux_core *muxc = priv->muxc;
        struct i2c_adapter *parent = muxc->parent;
        int ret;

        /* Select the right mux port and perform the transfer. */

        ret = muxc->select(muxc, priv->chan_id);
        if (ret >= 0)
                ret = __i2c_smbus_xfer(parent, addr, flags,
                                       read_write, command, size, data);
        if (muxc->deselect)
                muxc->deselect(muxc, 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_mux_core *muxc = priv->muxc;
        struct i2c_adapter *parent = muxc->parent;
        int ret;

        /* Select the right mux port and perform the transfer. */

        ret = muxc->select(muxc, priv->chan_id);
        if (ret >= 0)
                ret = i2c_smbus_xfer(parent, addr, flags,
                                     read_write, command, size, data);
        if (muxc->deselect)
                muxc->deselect(muxc, 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->muxc->parent;

        return parent->algo->functionality(parent);
}

/* Return all parent classes, merged */
static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
{
        unsigned int class = 0;

        do {
                class |= parent->class;
                parent = i2c_parent_is_i2c_adapter(parent);
        } while (parent);

        return class;
}

static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
        struct i2c_mux_priv *priv = adapter->algo_data;
        struct i2c_adapter *parent = priv->muxc->parent;

        rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
        if (!(flags & I2C_LOCK_ROOT_ADAPTER))
                return;
        i2c_lock_bus(parent, flags);
}

static int i2c_mux_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
        struct i2c_mux_priv *priv = adapter->algo_data;
        struct i2c_adapter *parent = priv->muxc->parent;

        if (!rt_mutex_trylock(&parent->mux_lock))
                return 0;       /* mux_lock not locked, failure */
        if (!(flags & I2C_LOCK_ROOT_ADAPTER))
                return 1;       /* we only want mux_lock, success */
        if (i2c_trylock_bus(parent, flags))
                return 1;       /* parent locked too, success */
        rt_mutex_unlock(&parent->mux_lock);
        return 0;               /* parent not locked, failure */
}

static void i2c_mux_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
        struct i2c_mux_priv *priv = adapter->algo_data;
        struct i2c_adapter *parent = priv->muxc->parent;

        if (flags & I2C_LOCK_ROOT_ADAPTER)
                i2c_unlock_bus(parent, flags);
        rt_mutex_unlock(&parent->mux_lock);
}

static void i2c_parent_lock_bus(struct i2c_adapter *adapter,
                                unsigned int flags)
{
        struct i2c_mux_priv *priv = adapter->algo_data;
        struct i2c_adapter *parent = priv->muxc->parent;

        rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter));
        i2c_lock_bus(parent, flags);
}

static int i2c_parent_trylock_bus(struct i2c_adapter *adapter,
                                  unsigned int flags)
{
        struct i2c_mux_priv *priv = adapter->algo_data;
        struct i2c_adapter *parent = priv->muxc->parent;

        if (!rt_mutex_trylock(&parent->mux_lock))
                return 0;       /* mux_lock not locked, failure */
        if (i2c_trylock_bus(parent, flags))
                return 1;       /* parent locked too, success */
        rt_mutex_unlock(&parent->mux_lock);
        return 0;               /* parent not locked, failure */
}

static void i2c_parent_unlock_bus(struct i2c_adapter *adapter,
                                  unsigned int flags)
{
        struct i2c_mux_priv *priv = adapter->algo_data;
        struct i2c_adapter *parent = priv->muxc->parent;

        i2c_unlock_bus(parent, flags);
        rt_mutex_unlock(&parent->mux_lock);
}

struct i2c_adapter *i2c_root_adapter(struct device *dev)
{
        struct device *i2c;
        struct i2c_adapter *i2c_root;

        /*
         * Walk up the device tree to find an i2c adapter, indicating
         * that this is an i2c client device. Check all ancestors to
         * handle mfd devices etc.
         */
        for (i2c = dev; i2c; i2c = i2c->parent) {
                if (i2c->type == &i2c_adapter_type)
                        break;
        }
        if (!i2c)
                return NULL;

        /* Continue up the tree to find the root i2c adapter */
        i2c_root = to_i2c_adapter(i2c);
        while (i2c_parent_is_i2c_adapter(i2c_root))
                i2c_root = i2c_parent_is_i2c_adapter(i2c_root);

        return i2c_root;
}
EXPORT_SYMBOL_GPL(i2c_root_adapter);

struct i2c_mux_core *i2c_mux_alloc(struct i2c_adapter *parent,
                                   struct device *dev, int max_adapters,
                                   int sizeof_priv, u32 flags,
                                   int (*select)(struct i2c_mux_core *, u32),
                                   int (*deselect)(struct i2c_mux_core *, u32))
{
        struct i2c_mux_core *muxc;

        muxc = devm_kzalloc(dev, struct_size(muxc, adapter, max_adapters)
                            + sizeof_priv, GFP_KERNEL);
        if (!muxc)
                return NULL;
        if (sizeof_priv)
                muxc->priv = &muxc->adapter[max_adapters];

        muxc->parent = parent;
        muxc->dev = dev;
        if (flags & I2C_MUX_LOCKED)
                muxc->mux_locked = true;
        if (flags & I2C_MUX_ARBITRATOR)
                muxc->arbitrator = true;
        if (flags & I2C_MUX_GATE)
                muxc->gate = true;
        muxc->select = select;
        muxc->deselect = deselect;
        muxc->max_adapters = max_adapters;

        return muxc;
}
EXPORT_SYMBOL_GPL(i2c_mux_alloc);

static const struct i2c_lock_operations i2c_mux_lock_ops = {
        .lock_bus =    i2c_mux_lock_bus,
        .trylock_bus = i2c_mux_trylock_bus,
        .unlock_bus =  i2c_mux_unlock_bus,
};

static const struct i2c_lock_operations i2c_parent_lock_ops = {
        .lock_bus =    i2c_parent_lock_bus,
        .trylock_bus = i2c_parent_trylock_bus,
        .unlock_bus =  i2c_parent_unlock_bus,
};

int i2c_mux_add_adapter(struct i2c_mux_core *muxc,
                        u32 force_nr, u32 chan_id,
                        unsigned int class)
{
        struct i2c_adapter *parent = muxc->parent;
        struct i2c_mux_priv *priv;
        char symlink_name[20];
        int ret;

        if (muxc->num_adapters >= muxc->max_adapters) {
                dev_err(muxc->dev, "No room for more i2c-mux adapters\n");
                return -EINVAL;
        }

        priv = kzalloc(sizeof(*priv), GFP_KERNEL);
        if (!priv)
                return -ENOMEM;

        /* Set up private adapter data */
        priv->muxc = muxc;
        priv->chan_id = chan_id;

        /* 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) {
                if (muxc->mux_locked)
                        priv->algo.master_xfer = i2c_mux_master_xfer;
                else
                        priv->algo.master_xfer = __i2c_mux_master_xfer;
        }
        if (parent->algo->master_xfer_atomic)
                priv->algo.master_xfer_atomic = priv->algo.master_xfer;

        if (parent->algo->smbus_xfer) {
                if (muxc->mux_locked)
                        priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
                else
                        priv->algo.smbus_xfer = __i2c_mux_smbus_xfer;
        }
        if (parent->algo->smbus_xfer_atomic)
                priv->algo.smbus_xfer_atomic = priv->algo.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.algo = &priv->algo;
        priv->adap.algo_data = priv;
        priv->adap.dev.parent = &parent->dev;
        priv->adap.retries = parent->retries;
        priv->adap.timeout = parent->timeout;
        priv->adap.quirks = parent->quirks;
        if (muxc->mux_locked)
                priv->adap.lock_ops = &i2c_mux_lock_ops;
        else
                priv->adap.lock_ops = &i2c_parent_lock_ops;

        /* Sanity check on class */
        if (i2c_mux_parent_classes(parent) & class)
                dev_err(&parent->dev,
                        "Segment %d behind mux can't share classes with ancestors\n",
                        chan_id);
        else
                priv->adap.class = class;

        /*
         * Try to populate the mux adapter's of_node, expands to
         * nothing if !CONFIG_OF.
         */
        if (muxc->dev->of_node) {
                struct device_node *dev_node = muxc->dev->of_node;
                struct device_node *mux_node, *child = NULL;
                u32 reg;

                if (muxc->arbitrator)
                        mux_node = of_get_child_by_name(dev_node, "i2c-arb");
                else if (muxc->gate)
                        mux_node = of_get_child_by_name(dev_node, "i2c-gate");
                else
                        mux_node = of_get_child_by_name(dev_node, "i2c-mux");

                if (mux_node) {
                        /* A "reg" property indicates an old-style DT entry */
                        if (!of_property_read_u32(mux_node, "reg", &reg)) {
                                of_node_put(mux_node);
                                mux_node = NULL;
                        }
                }

                if (!mux_node)
                        mux_node = of_node_get(dev_node);
                else if (muxc->arbitrator || muxc->gate)
                        child = of_node_get(mux_node);

                if (!child) {
                        for_each_child_of_node(mux_node, child) {
                                ret = of_property_read_u32(child, "reg", &reg);
                                if (ret)
                                        continue;
                                if (chan_id == reg)
                                        break;
                        }
                }

                priv->adap.dev.of_node = child;
                of_node_put(mux_node);
        }

        /*
         * Associate the mux channel with an ACPI node.
         */
        if (has_acpi_companion(muxc->dev))
                acpi_preset_companion(&priv->adap.dev,
                                      ACPI_COMPANION(muxc->dev),
                                      chan_id);

        if (force_nr) {
                priv->adap.nr = force_nr;
                ret = i2c_add_numbered_adapter(&priv->adap);
                if (ret < 0) {
                        dev_err(&parent->dev,
                                "failed to add mux-adapter %u as bus %u (error=%d)\n",
                                chan_id, force_nr, ret);
                        goto err_free_priv;
                }
        } else {
                ret = i2c_add_adapter(&priv->adap);
                if (ret < 0) {
                        dev_err(&parent->dev,
                                "failed to add mux-adapter %u (error=%d)\n",
                                chan_id, ret);
                        goto err_free_priv;
                }
        }

        WARN(sysfs_create_link(&priv->adap.dev.kobj, &muxc->dev->kobj,
                               "mux_device"),
             "can't create symlink to mux device\n");

        snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
        WARN(sysfs_create_link(&muxc->dev->kobj, &priv->adap.dev.kobj,
                               symlink_name),
             "can't create symlink to channel %u\n", chan_id);
        dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
                 i2c_adapter_id(&priv->adap));

        muxc->adapter[muxc->num_adapters++] = &priv->adap;
        return 0;

err_free_priv:
        kfree(priv);
        return ret;
}
EXPORT_SYMBOL_GPL(i2c_mux_add_adapter);

void i2c_mux_del_adapters(struct i2c_mux_core *muxc)
{
        char symlink_name[20];

        while (muxc->num_adapters) {
                struct i2c_adapter *adap = muxc->adapter[--muxc->num_adapters];
                struct i2c_mux_priv *priv = adap->algo_data;
                struct device_node *np = adap->dev.of_node;

                muxc->adapter[muxc->num_adapters] = NULL;

                snprintf(symlink_name, sizeof(symlink_name),
                         "channel-%u", priv->chan_id);
                sysfs_remove_link(&muxc->dev->kobj, symlink_name);

                sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
                i2c_del_adapter(adap);
                of_node_put(np);
                kfree(priv);
        }
}
EXPORT_SYMBOL_GPL(i2c_mux_del_adapters);

MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
MODULE_LICENSE("GPL v2");