Root/drivers/i2c/i2c-mux.c

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/of_i2c.h>
29
30/* multiplexer per channel data */
31struct i2c_mux_priv {
32    struct i2c_adapter adap;
33    struct i2c_algorithm algo;
34
35    struct i2c_adapter *parent;
36    void *mux_priv; /* the mux chip/device */
37    u32 chan_id; /* the channel 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
43static 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
61static 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 */
83static 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
91struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
92                struct device *mux_dev,
93                void *mux_priv, u32 force_nr, u32 chan_id,
94                int (*select) (struct i2c_adapter *,
95                           void *, u32),
96                int (*deselect) (struct i2c_adapter *,
97                         void *, u32))
98{
99    struct i2c_mux_priv *priv;
100    int ret;
101
102    priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
103    if (!priv)
104        return NULL;
105
106    /* Set up private adapter data */
107    priv->parent = parent;
108    priv->mux_priv = mux_priv;
109    priv->chan_id = chan_id;
110    priv->select = select;
111    priv->deselect = deselect;
112
113    /* Need to do algo dynamically because we don't know ahead
114     * of time what sort of physical adapter we'll be dealing with.
115     */
116    if (parent->algo->master_xfer)
117        priv->algo.master_xfer = i2c_mux_master_xfer;
118    if (parent->algo->smbus_xfer)
119        priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
120    priv->algo.functionality = i2c_mux_functionality;
121
122    /* Now fill out new adapter structure */
123    snprintf(priv->adap.name, sizeof(priv->adap.name),
124         "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
125    priv->adap.owner = THIS_MODULE;
126    priv->adap.algo = &priv->algo;
127    priv->adap.algo_data = priv;
128    priv->adap.dev.parent = &parent->dev;
129
130    /*
131     * Try to populate the mux adapter's of_node, expands to
132     * nothing if !CONFIG_OF.
133     */
134    if (mux_dev->of_node) {
135        struct device_node *child;
136        u32 reg;
137
138        for_each_child_of_node(mux_dev->of_node, child) {
139            ret = of_property_read_u32(child, "reg", &reg);
140            if (ret)
141                continue;
142            if (chan_id == reg) {
143                priv->adap.dev.of_node = child;
144                break;
145            }
146        }
147    }
148
149    if (force_nr) {
150        priv->adap.nr = force_nr;
151        ret = i2c_add_numbered_adapter(&priv->adap);
152    } else {
153        ret = i2c_add_adapter(&priv->adap);
154    }
155    if (ret < 0) {
156        dev_err(&parent->dev,
157            "failed to add mux-adapter (error=%d)\n",
158            ret);
159        kfree(priv);
160        return NULL;
161    }
162
163    dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
164         i2c_adapter_id(&priv->adap));
165
166    of_i2c_register_devices(&priv->adap);
167
168    return &priv->adap;
169}
170EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
171
172int i2c_del_mux_adapter(struct i2c_adapter *adap)
173{
174    struct i2c_mux_priv *priv = adap->algo_data;
175    int ret;
176
177    ret = i2c_del_adapter(adap);
178    if (ret < 0)
179        return ret;
180    kfree(priv);
181
182    return 0;
183}
184EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
185
186MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
187MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
188MODULE_LICENSE("GPL v2");
189

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