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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 */ |
31 | struct 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 | |
43 | static 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 | |
61 | static 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 */ |
83 | static 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 | |
91 | /* Return all parent classes, merged */ |
92 | static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent) |
93 | { |
94 | unsigned int class = 0; |
95 | |
96 | do { |
97 | class |= parent->class; |
98 | parent = i2c_parent_is_i2c_adapter(parent); |
99 | } while (parent); |
100 | |
101 | return class; |
102 | } |
103 | |
104 | struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent, |
105 | struct device *mux_dev, |
106 | void *mux_priv, u32 force_nr, u32 chan_id, |
107 | unsigned int class, |
108 | int (*select) (struct i2c_adapter *, |
109 | void *, u32), |
110 | int (*deselect) (struct i2c_adapter *, |
111 | void *, u32)) |
112 | { |
113 | struct i2c_mux_priv *priv; |
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 | |
144 | /* Sanity check on class */ |
145 | if (i2c_mux_parent_classes(parent) & class) |
146 | dev_err(&parent->dev, |
147 | "Segment %d behind mux can't share classes with ancestors\n", |
148 | chan_id); |
149 | else |
150 | priv->adap.class = class; |
151 | |
152 | /* |
153 | * Try to populate the mux adapter's of_node, expands to |
154 | * nothing if !CONFIG_OF. |
155 | */ |
156 | if (mux_dev->of_node) { |
157 | struct device_node *child; |
158 | u32 reg; |
159 | |
160 | for_each_child_of_node(mux_dev->of_node, child) { |
161 | ret = of_property_read_u32(child, "reg", ®); |
162 | if (ret) |
163 | continue; |
164 | if (chan_id == reg) { |
165 | priv->adap.dev.of_node = child; |
166 | break; |
167 | } |
168 | } |
169 | } |
170 | |
171 | if (force_nr) { |
172 | priv->adap.nr = force_nr; |
173 | ret = i2c_add_numbered_adapter(&priv->adap); |
174 | } else { |
175 | ret = i2c_add_adapter(&priv->adap); |
176 | } |
177 | if (ret < 0) { |
178 | dev_err(&parent->dev, |
179 | "failed to add mux-adapter (error=%d)\n", |
180 | ret); |
181 | kfree(priv); |
182 | return NULL; |
183 | } |
184 | |
185 | dev_info(&parent->dev, "Added multiplexed i2c bus %d\n", |
186 | i2c_adapter_id(&priv->adap)); |
187 | |
188 | of_i2c_register_devices(&priv->adap); |
189 | |
190 | return &priv->adap; |
191 | } |
192 | EXPORT_SYMBOL_GPL(i2c_add_mux_adapter); |
193 | |
194 | int i2c_del_mux_adapter(struct i2c_adapter *adap) |
195 | { |
196 | struct i2c_mux_priv *priv = adap->algo_data; |
197 | int ret; |
198 | |
199 | ret = i2c_del_adapter(adap); |
200 | if (ret < 0) |
201 | return ret; |
202 | kfree(priv); |
203 | |
204 | return 0; |
205 | } |
206 | EXPORT_SYMBOL_GPL(i2c_del_mux_adapter); |
207 | |
208 | MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>"); |
209 | MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses"); |
210 | MODULE_LICENSE("GPL v2"); |
211 |
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