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 struct device *mux_dev; 36 void *mux_priv; 37 u32 chan_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 /* Return all parent classes, merged */ 92 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent) 93 { 94 unsigned int class = 0; 95 96 do { 97 class |= parent->class; 98 parent = i2c_parent_is_i2c_adapter(parent); 99 } while (parent); 100 101 return class; 102 } 103 104 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent, 105 struct device *mux_dev, 106 void *mux_priv, u32 force_nr, u32 chan_id, 107 unsigned int class, 108 int (*select) (struct i2c_adapter *, 109 void *, u32), 110 int (*deselect) (struct i2c_adapter *, 111 void *, u32)) 112 { 113 struct i2c_mux_priv *priv; 114 char symlink_name[20]; 115 int ret; 116 117 priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL); 118 if (!priv) 119 return NULL; 120 121 /* Set up private adapter data */ 122 priv->parent = parent; 123 priv->mux_dev = mux_dev; 124 priv->mux_priv = mux_priv; 125 priv->chan_id = chan_id; 126 priv->select = select; 127 priv->deselect = deselect; 128 129 /* Need to do algo dynamically because we don't know ahead 130 * of time what sort of physical adapter we'll be dealing with. 131 */ 132 if (parent->algo->master_xfer) 133 priv->algo.master_xfer = i2c_mux_master_xfer; 134 if (parent->algo->smbus_xfer) 135 priv->algo.smbus_xfer = i2c_mux_smbus_xfer; 136 priv->algo.functionality = i2c_mux_functionality; 137 138 /* Now fill out new adapter structure */ 139 snprintf(priv->adap.name, sizeof(priv->adap.name), 140 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id); 141 priv->adap.owner = THIS_MODULE; 142 priv->adap.algo = &priv->algo; 143 priv->adap.algo_data = priv; 144 priv->adap.dev.parent = &parent->dev; 145 priv->adap.retries = parent->retries; 146 priv->adap.timeout = parent->timeout; 147 148 /* Sanity check on class */ 149 if (i2c_mux_parent_classes(parent) & class) 150 dev_err(&parent->dev, 151 "Segment %d behind mux can't share classes with ancestors\n", 152 chan_id); 153 else 154 priv->adap.class = class; 155 156 /* 157 * Try to populate the mux adapter's of_node, expands to 158 * nothing if !CONFIG_OF. 159 */ 160 if (mux_dev->of_node) { 161 struct device_node *child; 162 u32 reg; 163 164 for_each_child_of_node(mux_dev->of_node, child) { 165 ret = of_property_read_u32(child, "reg", ®); 166 if (ret) 167 continue; 168 if (chan_id == reg) { 169 priv->adap.dev.of_node = child; 170 break; 171 } 172 } 173 } 174 175 if (force_nr) { 176 priv->adap.nr = force_nr; 177 ret = i2c_add_numbered_adapter(&priv->adap); 178 } else { 179 ret = i2c_add_adapter(&priv->adap); 180 } 181 if (ret < 0) { 182 dev_err(&parent->dev, 183 "failed to add mux-adapter (error=%d)\n", 184 ret); 185 kfree(priv); 186 return NULL; 187 } 188 189 WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"), 190 "can't create symlink to mux device\n"); 191 192 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id); 193 WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name), 194 "can't create symlink for channel %u\n", chan_id); 195 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n", 196 i2c_adapter_id(&priv->adap)); 197 198 return &priv->adap; 199 } 200 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter); 201 202 void i2c_del_mux_adapter(struct i2c_adapter *adap) 203 { 204 struct i2c_mux_priv *priv = adap->algo_data; 205 char symlink_name[20]; 206 207 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id); 208 sysfs_remove_link(&priv->mux_dev->kobj, symlink_name); 209 210 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device"); 211 i2c_del_adapter(adap); 212 kfree(priv); 213 } 214 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter); 215 216 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 217 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses"); 218 MODULE_LICENSE("GPL v2"); 219