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#include <linux/of_i2c.h>
  29
  30/* multiplexer per channel data */
  31struct i2c_mux_priv {
  32        struct i2c_adapter adap;
  33        struct i2c_algorithm algo;
  34
  35        struct i2c_adapter *parent;
  36        void *mux_priv; /* the mux chip/device */
  37        u32  chan_id;   /* the channel id */
  38
  39        int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  40        int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  41};
  42
  43static int i2c_mux_master_xfer(struct i2c_adapter *adap,
  44                               struct i2c_msg msgs[], int num)
  45{
  46        struct i2c_mux_priv *priv = adap->algo_data;
  47        struct i2c_adapter *parent = priv->parent;
  48        int ret;
  49
  50        /* Switch to the right mux port and perform the transfer. */
  51
  52        ret = priv->select(parent, priv->mux_priv, priv->chan_id);
  53        if (ret >= 0)
  54                ret = parent->algo->master_xfer(parent, msgs, num);
  55        if (priv->deselect)
  56                priv->deselect(parent, priv->mux_priv, priv->chan_id);
  57
  58        return ret;
  59}
  60
  61static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
  62                              u16 addr, unsigned short flags,
  63                              char read_write, u8 command,
  64                              int size, union i2c_smbus_data *data)
  65{
  66        struct i2c_mux_priv *priv = adap->algo_data;
  67        struct i2c_adapter *parent = priv->parent;
  68        int ret;
  69
  70        /* Select the right mux port and perform the transfer. */
  71
  72        ret = priv->select(parent, priv->mux_priv, priv->chan_id);
  73        if (ret >= 0)
  74                ret = parent->algo->smbus_xfer(parent, addr, flags,
  75                                        read_write, command, size, data);
  76        if (priv->deselect)
  77                priv->deselect(parent, priv->mux_priv, priv->chan_id);
  78
  79        return ret;
  80}
  81
  82/* Return the parent's functionality */
  83static u32 i2c_mux_functionality(struct i2c_adapter *adap)
  84{
  85        struct i2c_mux_priv *priv = adap->algo_data;
  86        struct i2c_adapter *parent = priv->parent;
  87
  88        return parent->algo->functionality(parent);
  89}
  90
  91struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
  92                                struct device *mux_dev,
  93                                void *mux_priv, u32 force_nr, u32 chan_id,
  94                                int (*select) (struct i2c_adapter *,
  95                                               void *, u32),
  96                                int (*deselect) (struct i2c_adapter *,
  97                                                 void *, u32))
  98{
  99        struct i2c_mux_priv *priv;
 100        int ret;
 101
 102        priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
 103        if (!priv)
 104                return NULL;
 105
 106        /* Set up private adapter data */
 107        priv->parent = parent;
 108        priv->mux_priv = mux_priv;
 109        priv->chan_id = chan_id;
 110        priv->select = select;
 111        priv->deselect = deselect;
 112
 113        /* Need to do algo dynamically because we don't know ahead
 114         * of time what sort of physical adapter we'll be dealing with.
 115         */
 116        if (parent->algo->master_xfer)
 117                priv->algo.master_xfer = i2c_mux_master_xfer;
 118        if (parent->algo->smbus_xfer)
 119                priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 120        priv->algo.functionality = i2c_mux_functionality;
 121
 122        /* Now fill out new adapter structure */
 123        snprintf(priv->adap.name, sizeof(priv->adap.name),
 124                 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 125        priv->adap.owner = THIS_MODULE;
 126        priv->adap.algo = &priv->algo;
 127        priv->adap.algo_data = priv;
 128        priv->adap.dev.parent = &parent->dev;
 129
 130        /*
 131         * Try to populate the mux adapter's of_node, expands to
 132         * nothing if !CONFIG_OF.
 133         */
 134        if (mux_dev->of_node) {
 135                struct device_node *child;
 136                u32 reg;
 137
 138                for_each_child_of_node(mux_dev->of_node, child) {
 139                        ret = of_property_read_u32(child, "reg", &reg);
 140                        if (ret)
 141                                continue;
 142                        if (chan_id == reg) {
 143                                priv->adap.dev.of_node = child;
 144                                break;
 145                        }
 146                }
 147        }
 148
 149        if (force_nr) {
 150                priv->adap.nr = force_nr;
 151                ret = i2c_add_numbered_adapter(&priv->adap);
 152        } else {
 153                ret = i2c_add_adapter(&priv->adap);
 154        }
 155        if (ret < 0) {
 156                dev_err(&parent->dev,
 157                        "failed to add mux-adapter (error=%d)\n",
 158                        ret);
 159                kfree(priv);
 160                return NULL;
 161        }
 162
 163        dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 164                 i2c_adapter_id(&priv->adap));
 165
 166        of_i2c_register_devices(&priv->adap);
 167
 168        return &priv->adap;
 169}
 170EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 171
 172int i2c_del_mux_adapter(struct i2c_adapter *adap)
 173{
 174        struct i2c_mux_priv *priv = adap->algo_data;
 175        int ret;
 176
 177        ret = i2c_del_adapter(adap);
 178        if (ret < 0)
 179                return ret;
 180        kfree(priv);
 181
 182        return 0;
 183}
 184EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 185
 186MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 187MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 188MODULE_LICENSE("GPL v2");
 189
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