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