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 */
  31 struct 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
  44 static 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
  62 static 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 */
  84 static 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 */
  93 static 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
 105 struct 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 }
 209 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 210
 211 void 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 }
 223 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 224
 225 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 226 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 227 MODULE_LICENSE("GPL v2");