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Michael Lawnick08263742010-08-11 18:21:02 +02001/*
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>
David Daneybc454492012-04-12 14:14:23 -070027#include <linux/of.h>
Michael Lawnick08263742010-08-11 18:21:02 +020028
29/* multiplexer per channel data */
30struct i2c_mux_priv {
31 struct i2c_adapter adap;
32 struct i2c_algorithm algo;
33
34 struct i2c_adapter *parent;
David Daney5a3ecd52012-04-12 14:14:22 -070035 void *mux_priv; /* the mux chip/device */
Michael Lawnick08263742010-08-11 18:21:02 +020036 u32 chan_id; /* the channel id */
37
David Daney5a3ecd52012-04-12 14:14:22 -070038 int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
39 int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
Michael Lawnick08263742010-08-11 18:21:02 +020040};
41
42static 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
David Daney5a3ecd52012-04-12 14:14:22 -070051 ret = priv->select(parent, priv->mux_priv, priv->chan_id);
Michael Lawnick08263742010-08-11 18:21:02 +020052 if (ret >= 0)
53 ret = parent->algo->master_xfer(parent, msgs, num);
54 if (priv->deselect)
David Daney5a3ecd52012-04-12 14:14:22 -070055 priv->deselect(parent, priv->mux_priv, priv->chan_id);
Michael Lawnick08263742010-08-11 18:21:02 +020056
57 return ret;
58}
59
60static 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
David Daney5a3ecd52012-04-12 14:14:22 -070071 ret = priv->select(parent, priv->mux_priv, priv->chan_id);
Michael Lawnick08263742010-08-11 18:21:02 +020072 if (ret >= 0)
73 ret = parent->algo->smbus_xfer(parent, addr, flags,
74 read_write, command, size, data);
75 if (priv->deselect)
David Daney5a3ecd52012-04-12 14:14:22 -070076 priv->deselect(parent, priv->mux_priv, priv->chan_id);
Michael Lawnick08263742010-08-11 18:21:02 +020077
78 return ret;
79}
80
81/* Return the parent's functionality */
82static 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
Jean Delvareeee543e2012-10-05 22:23:51 +020090/* Return all parent classes, merged */
91static 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
Michael Lawnick08263742010-08-11 18:21:02 +0200103struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
David Daney5a3ecd52012-04-12 14:14:22 -0700104 struct device *mux_dev,
105 void *mux_priv, u32 force_nr, u32 chan_id,
Jean Delvareeee543e2012-10-05 22:23:51 +0200106 unsigned int class,
Michael Lawnick08263742010-08-11 18:21:02 +0200107 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;
David Daney5a3ecd52012-04-12 14:14:22 -0700121 priv->mux_priv = mux_priv;
Michael Lawnick08263742010-08-11 18:21:02 +0200122 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;
Michael Lawnick08263742010-08-11 18:21:02 +0200139 priv->adap.algo = &priv->algo;
140 priv->adap.algo_data = priv;
141 priv->adap.dev.parent = &parent->dev;
142
Jean Delvareeee543e2012-10-05 22:23:51 +0200143 /* 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
David Daneybc454492012-04-12 14:14:23 -0700151 /*
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", &reg);
161 if (ret)
162 continue;
163 if (chan_id == reg) {
164 priv->adap.dev.of_node = child;
165 break;
166 }
167 }
168 }
169
Michael Lawnick08263742010-08-11 18:21:02 +0200170 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
Michael Lawnick08263742010-08-11 18:21:02 +0200187 return &priv->adap;
188}
189EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
190
Lars-Peter Clausen51d95702013-03-09 08:16:49 +0000191void i2c_del_mux_adapter(struct i2c_adapter *adap)
Michael Lawnick08263742010-08-11 18:21:02 +0200192{
193 struct i2c_mux_priv *priv = adap->algo_data;
Michael Lawnick08263742010-08-11 18:21:02 +0200194
Lars-Peter Clausenbf51a8c2013-03-09 08:16:46 +0000195 i2c_del_adapter(adap);
Michael Lawnick08263742010-08-11 18:21:02 +0200196 kfree(priv);
Michael Lawnick08263742010-08-11 18:21:02 +0200197}
198EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
199
200MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
201MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
202MODULE_LICENSE("GPL v2");