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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
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;
35	void *mux_priv;	/* the mux chip/device */
36	u32  chan_id;	/* the channel id */
37
38	int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
39	int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
40};
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
51	ret = priv->select(parent, priv->mux_priv, priv->chan_id);
52	if (ret >= 0)
53		ret = parent->algo->master_xfer(parent, msgs, num);
54	if (priv->deselect)
55		priv->deselect(parent, priv->mux_priv, priv->chan_id);
56
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
71	ret = priv->select(parent, priv->mux_priv, priv->chan_id);
72	if (ret >= 0)
73		ret = parent->algo->smbus_xfer(parent, addr, flags,
74					read_write, command, size, data);
75	if (priv->deselect)
76		priv->deselect(parent, priv->mux_priv, priv->chan_id);
77
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
90/* 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
103struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
104				struct device *mux_dev,
105				void *mux_priv, u32 force_nr, u32 chan_id,
106				unsigned int class,
107				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;
121	priv->mux_priv = mux_priv;
122	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;
139	priv->adap.algo = &priv->algo;
140	priv->adap.algo_data = priv;
141	priv->adap.dev.parent = &parent->dev;
142	priv->adap.retries = parent->retries;
143	priv->adap.timeout = parent->timeout;
144
145	/* Sanity check on class */
146	if (i2c_mux_parent_classes(parent) & class)
147		dev_err(&parent->dev,
148			"Segment %d behind mux can't share classes with ancestors\n",
149			chan_id);
150	else
151		priv->adap.class = class;
152
153	/*
154	 * Try to populate the mux adapter's of_node, expands to
155	 * nothing if !CONFIG_OF.
156	 */
157	if (mux_dev->of_node) {
158		struct device_node *child;
159		u32 reg;
160
161		for_each_child_of_node(mux_dev->of_node, child) {
162			ret = of_property_read_u32(child, "reg", &reg);
163			if (ret)
164				continue;
165			if (chan_id == reg) {
166				priv->adap.dev.of_node = child;
167				break;
168			}
169		}
170	}
171
172	if (force_nr) {
173		priv->adap.nr = force_nr;
174		ret = i2c_add_numbered_adapter(&priv->adap);
175	} else {
176		ret = i2c_add_adapter(&priv->adap);
177	}
178	if (ret < 0) {
179		dev_err(&parent->dev,
180			"failed to add mux-adapter (error=%d)\n",
181			ret);
182		kfree(priv);
183		return NULL;
184	}
185
186	dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
187		 i2c_adapter_id(&priv->adap));
188
189	return &priv->adap;
190}
191EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
192
193void i2c_del_mux_adapter(struct i2c_adapter *adap)
194{
195	struct i2c_mux_priv *priv = adap->algo_data;
196
197	i2c_del_adapter(adap);
198	kfree(priv);
199}
200EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
201
202MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
203MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
204MODULE_LICENSE("GPL v2");
205