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 #include <linux/acpi.h> 29 30 /* multiplexer per channel data */ 31 struct i2c_mux_priv { 32 struct i2c_adapter adap; 33 struct i2c_algorithm algo; 34 35 struct i2c_adapter *parent; 36 struct device *mux_dev; 37 void *mux_priv; 38 u32 chan_id; 39 40 int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id); 41 int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id); 42 }; 43 44 static int i2c_mux_master_xfer(struct i2c_adapter *adap, 45 struct i2c_msg msgs[], int num) 46 { 47 struct i2c_mux_priv *priv = adap->algo_data; 48 struct i2c_adapter *parent = priv->parent; 49 int ret; 50 51 /* Switch to the right mux port and perform the transfer. */ 52 53 ret = priv->select(parent, priv->mux_priv, priv->chan_id); 54 if (ret >= 0) 55 ret = __i2c_transfer(parent, msgs, num); 56 if (priv->deselect) 57 priv->deselect(parent, priv->mux_priv, priv->chan_id); 58 59 return ret; 60 } 61 62 static int i2c_mux_smbus_xfer(struct i2c_adapter *adap, 63 u16 addr, unsigned short flags, 64 char read_write, u8 command, 65 int size, union i2c_smbus_data *data) 66 { 67 struct i2c_mux_priv *priv = adap->algo_data; 68 struct i2c_adapter *parent = priv->parent; 69 int ret; 70 71 /* Select the right mux port and perform the transfer. */ 72 73 ret = priv->select(parent, priv->mux_priv, priv->chan_id); 74 if (ret >= 0) 75 ret = parent->algo->smbus_xfer(parent, addr, flags, 76 read_write, command, size, data); 77 if (priv->deselect) 78 priv->deselect(parent, priv->mux_priv, priv->chan_id); 79 80 return ret; 81 } 82 83 /* Return the parent's functionality */ 84 static u32 i2c_mux_functionality(struct i2c_adapter *adap) 85 { 86 struct i2c_mux_priv *priv = adap->algo_data; 87 struct i2c_adapter *parent = priv->parent; 88 89 return parent->algo->functionality(parent); 90 } 91 92 /* Return all parent classes, merged */ 93 static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent) 94 { 95 unsigned int class = 0; 96 97 do { 98 class |= parent->class; 99 parent = i2c_parent_is_i2c_adapter(parent); 100 } while (parent); 101 102 return class; 103 } 104 105 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent, 106 struct device *mux_dev, 107 void *mux_priv, u32 force_nr, u32 chan_id, 108 unsigned int class, 109 int (*select) (struct i2c_adapter *, 110 void *, u32), 111 int (*deselect) (struct i2c_adapter *, 112 void *, u32)) 113 { 114 struct i2c_mux_priv *priv; 115 char symlink_name[20]; 116 int ret; 117 118 priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL); 119 if (!priv) 120 return NULL; 121 122 /* Set up private adapter data */ 123 priv->parent = parent; 124 priv->mux_dev = mux_dev; 125 priv->mux_priv = mux_priv; 126 priv->chan_id = chan_id; 127 priv->select = select; 128 priv->deselect = deselect; 129 130 /* Need to do algo dynamically because we don't know ahead 131 * of time what sort of physical adapter we'll be dealing with. 132 */ 133 if (parent->algo->master_xfer) 134 priv->algo.master_xfer = i2c_mux_master_xfer; 135 if (parent->algo->smbus_xfer) 136 priv->algo.smbus_xfer = i2c_mux_smbus_xfer; 137 priv->algo.functionality = i2c_mux_functionality; 138 139 /* Now fill out new adapter structure */ 140 snprintf(priv->adap.name, sizeof(priv->adap.name), 141 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id); 142 priv->adap.owner = THIS_MODULE; 143 priv->adap.algo = &priv->algo; 144 priv->adap.algo_data = priv; 145 priv->adap.dev.parent = &parent->dev; 146 priv->adap.retries = parent->retries; 147 priv->adap.timeout = parent->timeout; 148 priv->adap.quirks = parent->quirks; 149 150 /* Sanity check on class */ 151 if (i2c_mux_parent_classes(parent) & class) 152 dev_err(&parent->dev, 153 "Segment %d behind mux can't share classes with ancestors\n", 154 chan_id); 155 else 156 priv->adap.class = class; 157 158 /* 159 * Try to populate the mux adapter's of_node, expands to 160 * nothing if !CONFIG_OF. 161 */ 162 if (mux_dev->of_node) { 163 struct device_node *child; 164 u32 reg; 165 166 for_each_child_of_node(mux_dev->of_node, child) { 167 ret = of_property_read_u32(child, "reg", ®); 168 if (ret) 169 continue; 170 if (chan_id == reg) { 171 priv->adap.dev.of_node = child; 172 break; 173 } 174 } 175 } 176 177 /* 178 * Associate the mux channel with an ACPI node. 179 */ 180 if (has_acpi_companion(mux_dev)) 181 acpi_preset_companion(&priv->adap.dev, ACPI_COMPANION(mux_dev), 182 chan_id); 183 184 if (force_nr) { 185 priv->adap.nr = force_nr; 186 ret = i2c_add_numbered_adapter(&priv->adap); 187 } else { 188 ret = i2c_add_adapter(&priv->adap); 189 } 190 if (ret < 0) { 191 dev_err(&parent->dev, 192 "failed to add mux-adapter (error=%d)\n", 193 ret); 194 kfree(priv); 195 return NULL; 196 } 197 198 WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"), 199 "can't create symlink to mux device\n"); 200 201 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id); 202 WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name), 203 "can't create symlink for channel %u\n", chan_id); 204 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n", 205 i2c_adapter_id(&priv->adap)); 206 207 return &priv->adap; 208 } 209 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter); 210 211 void i2c_del_mux_adapter(struct i2c_adapter *adap) 212 { 213 struct i2c_mux_priv *priv = adap->algo_data; 214 char symlink_name[20]; 215 216 snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id); 217 sysfs_remove_link(&priv->mux_dev->kobj, symlink_name); 218 219 sysfs_remove_link(&priv->adap.dev.kobj, "mux_device"); 220 i2c_del_adapter(adap); 221 kfree(priv); 222 } 223 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter); 224 225 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); 226 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses"); 227 MODULE_LICENSE("GPL v2"); 228