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
  28 /* multiplexer per channel data */
  29 struct i2c_mux_priv {
  30         struct i2c_adapter adap;
  31         struct i2c_algorithm algo;
  32
  33         struct i2c_adapter *parent;
  34         void *mux_dev;  /* the mux chip/device */
  35         u32  chan_id;   /* the channel id */
  36
  37         int (*select)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
  38         int (*deselect)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
  39 };
  40
  41 static int i2c_mux_master_xfer(struct i2c_adapter *adap,
  42                                struct i2c_msg msgs[], int num)
  43 {
  44         struct i2c_mux_priv *priv = adap->algo_data;
  45         struct i2c_adapter *parent = priv->parent;
  46         int ret;
  47
  48         /* Switch to the right mux port and perform the transfer. */
  49
  50         ret = priv->select(parent, priv->mux_dev, priv->chan_id);
  51         if (ret >= 0)
  52                 ret = parent->algo->master_xfer(parent, msgs, num);
  53         if (priv->deselect)
  54                 priv->deselect(parent, priv->mux_dev, priv->chan_id);
  55
  56         return ret;
  57 }
  58
  59 static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
  60                               u16 addr, unsigned short flags,
  61                               char read_write, u8 command,
  62                               int size, union i2c_smbus_data *data)
  63 {
  64         struct i2c_mux_priv *priv = adap->algo_data;
  65         struct i2c_adapter *parent = priv->parent;
  66         int ret;
  67
  68         /* Select the right mux port and perform the transfer. */
  69
  70         ret = priv->select(parent, priv->mux_dev, priv->chan_id);
  71         if (ret >= 0)
  72                 ret = parent->algo->smbus_xfer(parent, addr, flags,
  73                                         read_write, command, size, data);
  74         if (priv->deselect)
  75                 priv->deselect(parent, priv->mux_dev, priv->chan_id);
  76
  77         return ret;
  78 }
  79
  80 /* Return the parent's functionality */
  81 static u32 i2c_mux_functionality(struct i2c_adapter *adap)
  82 {
  83         struct i2c_mux_priv *priv = adap->algo_data;
  84         struct i2c_adapter *parent = priv->parent;
  85
  86         return parent->algo->functionality(parent);
  87 }
  88
  89 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
  90                                 void *mux_dev, u32 force_nr, u32 chan_id,
  91                                 int (*select) (struct i2c_adapter *,
  92                                                void *, u32),
  93                                 int (*deselect) (struct i2c_adapter *,
  94                                                  void *, u32))
  95 {
  96         struct i2c_mux_priv *priv;
  97         int ret;
  98
  99         priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
 100         if (!priv)
 101                 return NULL;
 102
 103         /* Set up private adapter data */
 104         priv->parent = parent;
 105         priv->mux_dev = mux_dev;
 106         priv->chan_id = chan_id;
 107         priv->select = select;
 108         priv->deselect = deselect;
 109
 110         /* Need to do algo dynamically because we don't know ahead
 111          * of time what sort of physical adapter we'll be dealing with.
 112          */
 113         if (parent->algo->master_xfer)
 114                 priv->algo.master_xfer = i2c_mux_master_xfer;
 115         if (parent->algo->smbus_xfer)
 116                 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
 117         priv->algo.functionality = i2c_mux_functionality;
 118
 119         /* Now fill out new adapter structure */
 120         snprintf(priv->adap.name, sizeof(priv->adap.name),
 121                  "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
 122         priv->adap.owner = THIS_MODULE;
 123         priv->adap.algo = &priv->algo;
 124         priv->adap.algo_data = priv;
 125         priv->adap.dev.parent = &parent->dev;
 126
 127         if (force_nr) {
 128                 priv->adap.nr = force_nr;
 129                 ret = i2c_add_numbered_adapter(&priv->adap);
 130         } else {
 131                 ret = i2c_add_adapter(&priv->adap);
 132         }
 133         if (ret < 0) {
 134                 dev_err(&parent->dev,
 135                         "failed to add mux-adapter (error=%d)\n",
 136                         ret);
 137                 kfree(priv);
 138                 return NULL;
 139         }
 140
 141         dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 142                  i2c_adapter_id(&priv->adap));
 143
 144         return &priv->adap;
 145 }
 146 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
 147
 148 int i2c_del_mux_adapter(struct i2c_adapter *adap)
 149 {
 150         struct i2c_mux_priv *priv = adap->algo_data;
 151         int ret;
 152
 153         ret = i2c_del_adapter(adap);
 154         if (ret < 0)
 155                 return ret;
 156         kfree(priv);
 157
 158         return 0;
 159 }
 160 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
 161
 162 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
 163 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
 164 MODULE_LICENSE("GPL v2");