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 #include <linux/of_i2c.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         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
  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 = 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
  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 struct 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 }
 170 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 171
 172 int 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 }
 184 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 185
 186 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 187 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 188 MODULE_LICENSE("GPL v2");