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", ®); 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"); 203