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/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 */
  30 struct i2c_mux_priv {
  31         struct i2c_adapter adap;
  32         struct i2c_algorithm algo;
  33
  34         struct i2c_adapter *parent;
  35         struct device *mux_dev;
  36         void *mux_priv;
  37         u32 chan_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
  43 static 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 = __i2c_transfer(parent, msgs, num);
  55         if (priv->deselect)
  56                 priv->deselect(parent, priv->mux_priv, priv->chan_id);
  57
  58         return ret;
  59 }
  60
  61 static 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 */
  83 static 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
  91 /* Return all parent classes, merged */
  92 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
  93 {
  94         unsigned int class = 0;
  95
  96         do {
  97                 class |= parent->class;
  98                 parent = i2c_parent_is_i2c_adapter(parent);
  99         } while (parent);
 100
 101         return class;
 102 }
 103
 104 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
 105                                 struct device *mux_dev,
 106                                 void *mux_priv, u32 force_nr, u32 chan_id,
 107                                 unsigned int class,
 108                                 int (*select) (struct i2c_adapter *,
 109                                                void *, u32),
 110                                 int (*deselect) (struct i2c_adapter *,
 111                                                  void *, u32))
 112 {
 113         struct i2c_mux_priv *priv;
 114         char symlink_name[20];
 115         int ret;
 116
 117         priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
 118         if (!priv)
 119                 return NULL;
 120
 121         /* Set up private adapter data */
 122         priv->parent = parent;
 123         priv->mux_dev = mux_dev;
 124         priv->mux_priv = mux_priv;
 125         priv->chan_id = chan_id;
 126         priv->select = select;
 127         priv->deselect = deselect;
 128
 129         /* Need to do algo dynamically because we don't know ahead
 130          * of time what sort of physical adapter we'll be dealing with.
 131          */
 132         if (parent->algo->master_xfer)
 133                 priv->algo.master_xfer = i2c_mux_master_xfer;
 134         if (parent->algo->smbus_xfer)
 135                 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 136         priv->algo.functionality = i2c_mux_functionality;
 137
 138         /* Now fill out new adapter structure */
 139         snprintf(priv->adap.name, sizeof(priv->adap.name),
 140                  "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 141         priv->adap.owner = THIS_MODULE;
 142         priv->adap.algo = &priv->algo;
 143         priv->adap.algo_data = priv;
 144         priv->adap.dev.parent = &parent->dev;
 145         priv->adap.retries = parent->retries;
 146         priv->adap.timeout = parent->timeout;
 147         priv->adap.quirks = parent->quirks;
 148
 149         /* Sanity check on class */
 150         if (i2c_mux_parent_classes(parent) & class)
 151                 dev_err(&parent->dev,
 152                         "Segment %d behind mux can't share classes with ancestors\n",
 153                         chan_id);
 154         else
 155                 priv->adap.class = class;
 156
 157         /*
 158          * Try to populate the mux adapter's of_node, expands to
 159          * nothing if !CONFIG_OF.
 160          */
 161         if (mux_dev->of_node) {
 162                 struct device_node *child;
 163                 u32 reg;
 164
 165                 for_each_child_of_node(mux_dev->of_node, child) {
 166                         ret = of_property_read_u32(child, "reg", &reg);
 167                         if (ret)
 168                                 continue;
 169                         if (chan_id == reg) {
 170                                 priv->adap.dev.of_node = child;
 171                                 break;
 172                         }
 173                 }
 174         }
 175
 176         if (force_nr) {
 177                 priv->adap.nr = force_nr;
 178                 ret = i2c_add_numbered_adapter(&priv->adap);
 179         } else {
 180                 ret = i2c_add_adapter(&priv->adap);
 181         }
 182         if (ret < 0) {
 183                 dev_err(&parent->dev,
 184                         "failed to add mux-adapter (error=%d)\n",
 185                         ret);
 186                 kfree(priv);
 187                 return NULL;
 188         }
 189
 190         WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"),
 191                                "can't create symlink to mux device\n");
 192
 193         snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
 194         WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name),
 195                                "can't create symlink for channel %u\n", chan_id);
 196         dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 197                  i2c_adapter_id(&priv->adap));
 198
 199         return &priv->adap;
 200 }
 201 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 202
 203 void i2c_del_mux_adapter(struct i2c_adapter *adap)
 204 {
 205         struct i2c_mux_priv *priv = adap->algo_data;
 206         char symlink_name[20];
 207
 208         snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id);
 209         sysfs_remove_link(&priv->mux_dev->kobj, symlink_name);
 210
 211         sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
 212         i2c_del_adapter(adap);
 213         kfree(priv);
 214 }
 215 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 216
 217 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 218 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 219 MODULE_LICENSE("GPL v2");