linux/drivers/i2c/i2c-mux.c
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   1/*
   2 * Multiplexed I2C bus driver.
   3 *
   4 * Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
   5 * Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
   6 * Copyright (c) 2009-2010 NSN GmbH & Co KG <michael.lawnick.ext@nsn.com>
   7 *
   8 * Simplifies access to complex multiplexed I2C bus topologies, by presenting
   9 * each multiplexed bus segment as an additional I2C adapter.
  10 * Supports multi-level mux'ing (mux behind a mux).
  11 *
  12 * Based on:
  13 *      i2c-virt.c from Kumar Gala <galak@kernel.crashing.org>
  14 *      i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc.
  15 *      i2c-virtual.c from Brian Kuschak <bkuschak@yahoo.com>
  16 *
  17 * This file is licensed under the terms of the GNU General Public
  18 * License version 2. This program is licensed "as is" without any
  19 * warranty of any kind, whether express or implied.
  20 */
  21
  22#include <linux/kernel.h>
  23#include <linux/module.h>
  24#include <linux/slab.h>
  25#include <linux/i2c.h>
  26#include <linux/i2c-mux.h>
  27#include <linux/of.h>
  28
  29/* multiplexer per channel data */
  30struct i2c_mux_priv {
  31        struct i2c_adapter adap;
  32        struct i2c_algorithm algo;
  33
  34        struct i2c_adapter *parent;
  35        void *mux_priv; /* the mux chip/device */
  36        u32  chan_id;   /* the channel id */
  37
  38        int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  39        int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  40};
  41
  42static int i2c_mux_master_xfer(struct i2c_adapter *adap,
  43                               struct i2c_msg msgs[], int num)
  44{
  45        struct i2c_mux_priv *priv = adap->algo_data;
  46        struct i2c_adapter *parent = priv->parent;
  47        int ret;
  48
  49        /* Switch to the right mux port and perform the transfer. */
  50
  51        ret = priv->select(parent, priv->mux_priv, priv->chan_id);
  52        if (ret >= 0)
  53                ret = parent->algo->master_xfer(parent, msgs, num);
  54        if (priv->deselect)
  55                priv->deselect(parent, priv->mux_priv, priv->chan_id);
  56
  57        return ret;
  58}
  59
  60static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
  61                              u16 addr, unsigned short flags,
  62                              char read_write, u8 command,
  63                              int size, union i2c_smbus_data *data)
  64{
  65        struct i2c_mux_priv *priv = adap->algo_data;
  66        struct i2c_adapter *parent = priv->parent;
  67        int ret;
  68
  69        /* Select the right mux port and perform the transfer. */
  70
  71        ret = priv->select(parent, priv->mux_priv, priv->chan_id);
  72        if (ret >= 0)
  73                ret = parent->algo->smbus_xfer(parent, addr, flags,
  74                                        read_write, command, size, data);
  75        if (priv->deselect)
  76                priv->deselect(parent, priv->mux_priv, priv->chan_id);
  77
  78        return ret;
  79}
  80
  81/* Return the parent's functionality */
  82static u32 i2c_mux_functionality(struct i2c_adapter *adap)
  83{
  84        struct i2c_mux_priv *priv = adap->algo_data;
  85        struct i2c_adapter *parent = priv->parent;
  86
  87        return parent->algo->functionality(parent);
  88}
  89
  90/* Return all parent classes, merged */
  91static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
  92{
  93        unsigned int class = 0;
  94
  95        do {
  96                class |= parent->class;
  97                parent = i2c_parent_is_i2c_adapter(parent);
  98        } while (parent);
  99
 100        return class;
 101}
 102
 103struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
 104                                struct device *mux_dev,
 105                                void *mux_priv, u32 force_nr, u32 chan_id,
 106                                unsigned int class,
 107                                int (*select) (struct i2c_adapter *,
 108                                               void *, u32),
 109                                int (*deselect) (struct i2c_adapter *,
 110                                                 void *, u32))
 111{
 112        struct i2c_mux_priv *priv;
 113        int ret;
 114
 115        priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
 116        if (!priv)
 117                return NULL;
 118
 119        /* Set up private adapter data */
 120        priv->parent = parent;
 121        priv->mux_priv = mux_priv;
 122        priv->chan_id = chan_id;
 123        priv->select = select;
 124        priv->deselect = deselect;
 125
 126        /* Need to do algo dynamically because we don't know ahead
 127         * of time what sort of physical adapter we'll be dealing with.
 128         */
 129        if (parent->algo->master_xfer)
 130                priv->algo.master_xfer = i2c_mux_master_xfer;
 131        if (parent->algo->smbus_xfer)
 132                priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 133        priv->algo.functionality = i2c_mux_functionality;
 134
 135        /* Now fill out new adapter structure */
 136        snprintf(priv->adap.name, sizeof(priv->adap.name),
 137                 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 138        priv->adap.owner = THIS_MODULE;
 139        priv->adap.algo = &priv->algo;
 140        priv->adap.algo_data = priv;
 141        priv->adap.dev.parent = &parent->dev;
 142
 143        /* Sanity check on class */
 144        if (i2c_mux_parent_classes(parent) & class)
 145                dev_err(&parent->dev,
 146                        "Segment %d behind mux can't share classes with ancestors\n",
 147                        chan_id);
 148        else
 149                priv->adap.class = class;
 150
 151        /*
 152         * Try to populate the mux adapter's of_node, expands to
 153         * nothing if !CONFIG_OF.
 154         */
 155        if (mux_dev->of_node) {
 156                struct device_node *child;
 157                u32 reg;
 158
 159                for_each_child_of_node(mux_dev->of_node, child) {
 160                        ret = of_property_read_u32(child, "reg", &reg);
 161                        if (ret)
 162                                continue;
 163                        if (chan_id == reg) {
 164                                priv->adap.dev.of_node = child;
 165                                break;
 166                        }
 167                }
 168        }
 169
 170        if (force_nr) {
 171                priv->adap.nr = force_nr;
 172                ret = i2c_add_numbered_adapter(&priv->adap);
 173        } else {
 174                ret = i2c_add_adapter(&priv->adap);
 175        }
 176        if (ret < 0) {
 177                dev_err(&parent->dev,
 178                        "failed to add mux-adapter (error=%d)\n",
 179                        ret);
 180                kfree(priv);
 181                return NULL;
 182        }
 183
 184        dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 185                 i2c_adapter_id(&priv->adap));
 186
 187        return &priv->adap;
 188}
 189EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 190
 191void i2c_del_mux_adapter(struct i2c_adapter *adap)
 192{
 193        struct i2c_mux_priv *priv = adap->algo_data;
 194
 195        i2c_del_adapter(adap);
 196        kfree(priv);
 197}
 198EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 199
 200MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 201MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 202MODULE_LICENSE("GPL v2");
 203
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