/*
   * 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>
  #include <linux/of.h>
  #include <linux/acpi.h>
  
  /* multiplexer per channel data */
  struct i2c_mux_priv {
  	struct i2c_adapter adap;
  	struct i2c_algorithm algo;
  
  	struct i2c_adapter *parent;
  	struct device *mux_dev;
  	void *mux_priv;
  	u32 chan_id;
  
  	int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  	int (*deselect)(struct i2c_adapter *, void *mux_priv, 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_priv, priv->chan_id);
  	if (ret >= 0)
  		ret = __i2c_transfer(parent, msgs, num);
  	if (priv->deselect)
  		priv->deselect(parent, priv->mux_priv, 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_priv, 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_priv, 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);
  }
  
  /* 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;
  }
  
  struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
  				struct device *mux_dev,
  				void *mux_priv, u32 force_nr, u32 chan_id,
  				unsigned int class,
  				int (*select) (struct i2c_adapter *,
  					       void *, u32),
  				int (*deselect) (struct i2c_adapter *,
  						 void *, u32))
  {
  	struct i2c_mux_priv *priv;
  	char symlink_name[20];
  	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->mux_priv = mux_priv;
  	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.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;
  
  	/* 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
  ",
  			chan_id);
  	else
  		priv->adap.class = class;
  
  	/*
  	 * 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;
  			}
  		}
  	}
  
  	/*
  	 * Associate the mux channel with an ACPI node.
  	 */
  	if (has_acpi_companion(mux_dev))
  		acpi_preset_companion(&priv->adap.dev, ACPI_COMPANION(mux_dev),
  				      chan_id);
  
  	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)
  ",
  			ret);
  		kfree(priv);
  		return NULL;
  	}
  
  	WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"),
  			       "can't create symlink to mux device
  ");
  
  	snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
  	WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name),
  			       "can't create symlink for channel %u
  ", chan_id);
  	dev_info(&parent->dev, "Added multiplexed i2c bus %d
  ",
  		 i2c_adapter_id(&priv->adap));
  
  	return &priv->adap;
  }
  EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
  
  void i2c_del_mux_adapter(struct i2c_adapter *adap)
  {
  	struct i2c_mux_priv *priv = adap->algo_data;
  	char symlink_name[20];
  
  	snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id);
  	sysfs_remove_link(&priv->mux_dev->kobj, symlink_name);
  
  	sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
  	i2c_del_adapter(adap);
  	kfree(priv);
  }
  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");