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         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
  42 static 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
  60 static 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 */
  82 static 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 */
  91 static 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
 103 struct 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 }
 189 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 190
 191 void 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 }
 198 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 199
 200 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 201 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 202 MODULE_LICENSE("GPL v2");