LXR linux/drivers/i2c/i2c-mux.c

   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/acpi.h>
  23#include <linux/i2c.h>
  24#include <linux/i2c-mux.h>
  25#include <linux/kernel.h>
  26#include <linux/module.h>
  27#include <linux/of.h>
  28#include <linux/slab.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        struct device *mux_dev;
  37        void *mux_priv;
  38        u32 chan_id;
  39
  40        int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  41        int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
  42};
  43
  44static int i2c_mux_master_xfer(struct i2c_adapter *adap,
  45                               struct i2c_msg msgs[], int num)
  46{
  47        struct i2c_mux_priv *priv = adap->algo_data;
  48        struct i2c_adapter *parent = priv->parent;
  49        int ret;
  50
  51        /* Switch to the right mux port and perform the transfer. */
  52
  53        ret = priv->select(parent, priv->mux_priv, priv->chan_id);
  54        if (ret >= 0)
  55                ret = __i2c_transfer(parent, msgs, num);
  56        if (priv->deselect)
  57                priv->deselect(parent, priv->mux_priv, priv->chan_id);
  58
  59        return ret;
  60}
  61
  62static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
  63                              u16 addr, unsigned short flags,
  64                              char read_write, u8 command,
  65                              int size, union i2c_smbus_data *data)
  66{
  67        struct i2c_mux_priv *priv = adap->algo_data;
  68        struct i2c_adapter *parent = priv->parent;
  69        int ret;
  70
  71        /* Select the right mux port and perform the transfer. */
  72
  73        ret = priv->select(parent, priv->mux_priv, priv->chan_id);
  74        if (ret >= 0)
  75                ret = parent->algo->smbus_xfer(parent, addr, flags,
  76                                        read_write, command, size, data);
  77        if (priv->deselect)
  78                priv->deselect(parent, priv->mux_priv, priv->chan_id);
  79
  80        return ret;
  81}
  82
  83/* Return the parent's functionality */
  84static u32 i2c_mux_functionality(struct i2c_adapter *adap)
  85{
  86        struct i2c_mux_priv *priv = adap->algo_data;
  87        struct i2c_adapter *parent = priv->parent;
  88
  89        return parent->algo->functionality(parent);
  90}
  91
  92/* Return all parent classes, merged */
  93static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
  94{
  95        unsigned int class = 0;
  96
  97        do {
  98                class |= parent->class;
  99                parent = i2c_parent_is_i2c_adapter(parent);
 100        } while (parent);
 101
 102        return class;
 103}
 104
 105struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
 106                                struct device *mux_dev,
 107                                void *mux_priv, u32 force_nr, u32 chan_id,
 108                                unsigned int class,
 109                                int (*select) (struct i2c_adapter *,
 110                                               void *, u32),
 111                                int (*deselect) (struct i2c_adapter *,
 112                                                 void *, u32))
 113{
 114        struct i2c_mux_priv *priv;
 115        char symlink_name[20];
 116        int ret;
 117
 118        priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
 119        if (!priv)
 120                return NULL;
 121
 122        /* Set up private adapter data */
 123        priv->parent = parent;
 124        priv->mux_dev = mux_dev;
 125        priv->mux_priv = mux_priv;
 126        priv->chan_id = chan_id;
 127        priv->select = select;
 128        priv->deselect = deselect;
 129
 130        /* Need to do algo dynamically because we don't know ahead
 131         * of time what sort of physical adapter we'll be dealing with.
 132         */
 133        if (parent->algo->master_xfer)
 134                priv->algo.master_xfer = i2c_mux_master_xfer;
 135        if (parent->algo->smbus_xfer)
 136                priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 137        priv->algo.functionality = i2c_mux_functionality;
 138
 139        /* Now fill out new adapter structure */
 140        snprintf(priv->adap.name, sizeof(priv->adap.name),
 141                 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 142        priv->adap.owner = THIS_MODULE;
 143        priv->adap.algo = &priv->algo;
 144        priv->adap.algo_data = priv;
 145        priv->adap.dev.parent = &parent->dev;
 146        priv->adap.retries = parent->retries;
 147        priv->adap.timeout = parent->timeout;
 148        priv->adap.quirks = parent->quirks;
 149
 150        /* Sanity check on class */
 151        if (i2c_mux_parent_classes(parent) & class)
 152                dev_err(&parent->dev,
 153                        "Segment %d behind mux can't share classes with ancestors\n",
 154                        chan_id);
 155        else
 156                priv->adap.class = class;
 157
 158        /*
 159         * Try to populate the mux adapter's of_node, expands to
 160         * nothing if !CONFIG_OF.
 161         */
 162        if (mux_dev->of_node) {
 163                struct device_node *child;
 164                u32 reg;
 165
 166                for_each_child_of_node(mux_dev->of_node, child) {
 167                        ret = of_property_read_u32(child, "reg", &reg);
 168                        if (ret)
 169                                continue;
 170                        if (chan_id == reg) {
 171                                priv->adap.dev.of_node = child;
 172                                break;
 173                        }
 174                }
 175        }
 176
 177        /*
 178         * Associate the mux channel with an ACPI node.
 179         */
 180        if (has_acpi_companion(mux_dev))
 181                acpi_preset_companion(&priv->adap.dev, ACPI_COMPANION(mux_dev),
 182                                      chan_id);
 183
 184        if (force_nr) {
 185                priv->adap.nr = force_nr;
 186                ret = i2c_add_numbered_adapter(&priv->adap);
 187        } else {
 188                ret = i2c_add_adapter(&priv->adap);
 189        }
 190        if (ret < 0) {
 191                dev_err(&parent->dev,
 192                        "failed to add mux-adapter (error=%d)\n",
 193                        ret);
 194                kfree(priv);
 195                return NULL;
 196        }
 197
 198        WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"),
 199                               "can't create symlink to mux device\n");
 200
 201        snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
 202        WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name),
 203                               "can't create symlink for channel %u\n", chan_id);
 204        dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 205                 i2c_adapter_id(&priv->adap));
 206
 207        return &priv->adap;
 208}
 209EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 210
 211void i2c_del_mux_adapter(struct i2c_adapter *adap)
 212{
 213        struct i2c_mux_priv *priv = adap->algo_data;
 214        char symlink_name[20];
 215
 216        snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id);
 217        sysfs_remove_link(&priv->mux_dev->kobj, symlink_name);
 218
 219        sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
 220        i2c_del_adapter(adap);
 221        kfree(priv);
 222}
 223EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 224
 225MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 226MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 227MODULE_LICENSE("GPL v2");
 228