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
28 /* multiplexer per channel data */
29 struct i2c_mux_priv {
30 struct i2c_adapter adap;
31 struct i2c_algorithm algo;
32
33 struct i2c_adapter *parent;
34 void *mux_dev; /* the mux chip/device */
35 u32 chan_id; /* the channel id */
36
37 int (*select)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
38 int (*deselect)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
39 };
40
i2c_mux_master_xfer(struct i2c_adapter * adap,struct i2c_msg msgs[],int num)41 static int i2c_mux_master_xfer(struct i2c_adapter *adap,
42 struct i2c_msg msgs[], int num)
43 {
44 struct i2c_mux_priv *priv = adap->algo_data;
45 struct i2c_adapter *parent = priv->parent;
46 int ret;
47
48 /* Switch to the right mux port and perform the transfer. */
49
50 ret = priv->select(parent, priv->mux_dev, priv->chan_id);
51 if (ret >= 0)
52 ret = parent->algo->master_xfer(parent, msgs, num);
53 if (priv->deselect)
54 priv->deselect(parent, priv->mux_dev, priv->chan_id);
55
56 return ret;
57 }
58
i2c_mux_smbus_xfer(struct i2c_adapter * adap,u16 addr,unsigned short flags,char read_write,u8 command,int size,union i2c_smbus_data * data)59 static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
60 u16 addr, unsigned short flags,
61 char read_write, u8 command,
62 int size, union i2c_smbus_data *data)
63 {
64 struct i2c_mux_priv *priv = adap->algo_data;
65 struct i2c_adapter *parent = priv->parent;
66 int ret;
67
68 /* Select the right mux port and perform the transfer. */
69
70 ret = priv->select(parent, priv->mux_dev, priv->chan_id);
71 if (ret >= 0)
72 ret = parent->algo->smbus_xfer(parent, addr, flags,
73 read_write, command, size, data);
74 if (priv->deselect)
75 priv->deselect(parent, priv->mux_dev, priv->chan_id);
76
77 return ret;
78 }
79
80 /* Return the parent's functionality */
i2c_mux_functionality(struct i2c_adapter * adap)81 static u32 i2c_mux_functionality(struct i2c_adapter *adap)
82 {
83 struct i2c_mux_priv *priv = adap->algo_data;
84 struct i2c_adapter *parent = priv->parent;
85
86 return parent->algo->functionality(parent);
87 }
88
i2c_add_mux_adapter(struct i2c_adapter * parent,void * mux_dev,u32 force_nr,u32 chan_id,int (* select)(struct i2c_adapter *,void *,u32),int (* deselect)(struct i2c_adapter *,void *,u32))89 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
90 void *mux_dev, u32 force_nr, u32 chan_id,
91 int (*select) (struct i2c_adapter *,
92 void *, u32),
93 int (*deselect) (struct i2c_adapter *,
94 void *, u32))
95 {
96 struct i2c_mux_priv *priv;
97 int ret;
98
99 priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
100 if (!priv)
101 return NULL;
102
103 /* Set up private adapter data */
104 priv->parent = parent;
105 priv->mux_dev = mux_dev;
106 priv->chan_id = chan_id;
107 priv->select = select;
108 priv->deselect = deselect;
109
110 /* Need to do algo dynamically because we don't know ahead
111 * of time what sort of physical adapter we'll be dealing with.
112 */
113 if (parent->algo->master_xfer)
114 priv->algo.master_xfer = i2c_mux_master_xfer;
115 if (parent->algo->smbus_xfer)
116 priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
117 priv->algo.functionality = i2c_mux_functionality;
118
119 /* Now fill out new adapter structure */
120 snprintf(priv->adap.name, sizeof(priv->adap.name),
121 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
122 priv->adap.owner = THIS_MODULE;
123 priv->adap.algo = &priv->algo;
124 priv->adap.algo_data = priv;
125 priv->adap.dev.parent = &parent->dev;
126
127 if (force_nr) {
128 priv->adap.nr = force_nr;
129 ret = i2c_add_numbered_adapter(&priv->adap);
130 } else {
131 ret = i2c_add_adapter(&priv->adap);
132 }
133 if (ret < 0) {
134 dev_err(&parent->dev,
135 "failed to add mux-adapter (error=%d)\n",
136 ret);
137 kfree(priv);
138 return NULL;
139 }
140
141 dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
142 i2c_adapter_id(&priv->adap));
143
144 return &priv->adap;
145 }
146 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
147
i2c_del_mux_adapter(struct i2c_adapter * adap)148 int i2c_del_mux_adapter(struct i2c_adapter *adap)
149 {
150 struct i2c_mux_priv *priv = adap->algo_data;
151 int ret;
152
153 ret = i2c_del_adapter(adap);
154 if (ret < 0)
155 return ret;
156 kfree(priv);
157
158 return 0;
159 }
160 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
161
162 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
163 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
164 MODULE_LICENSE("GPL v2");
165