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"); 165