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	struct device *mux_dev;
36	void *mux_priv;
37	u32 chan_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 = __i2c_transfer(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
91/* Return all parent classes, merged */
92static 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
104struct 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	char symlink_name[20];
115	int ret;
116
117	priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
118	if (!priv)
119		return NULL;
120
121	/* Set up private adapter data */
122	priv->parent = parent;
123	priv->mux_dev = mux_dev;
124	priv->mux_priv = mux_priv;
125	priv->chan_id = chan_id;
126	priv->select = select;
127	priv->deselect = deselect;
128
129	/* Need to do algo dynamically because we don't know ahead
130	 * of time what sort of physical adapter we'll be dealing with.
131	 */
132	if (parent->algo->master_xfer)
133		priv->algo.master_xfer = i2c_mux_master_xfer;
134	if (parent->algo->smbus_xfer)
135		priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
136	priv->algo.functionality = i2c_mux_functionality;
137
138	/* Now fill out new adapter structure */
139	snprintf(priv->adap.name, sizeof(priv->adap.name),
140		 "i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
141	priv->adap.owner = THIS_MODULE;
142	priv->adap.algo = &priv->algo;
143	priv->adap.algo_data = priv;
144	priv->adap.dev.parent = &parent->dev;
145	priv->adap.retries = parent->retries;
146	priv->adap.timeout = parent->timeout;
147	priv->adap.quirks = parent->quirks;
148
149	/* Sanity check on class */
150	if (i2c_mux_parent_classes(parent) & class)
151		dev_err(&parent->dev,
152			"Segment %d behind mux can't share classes with ancestors\n",
153			chan_id);
154	else
155		priv->adap.class = class;
156
157	/*
158	 * Try to populate the mux adapter's of_node, expands to
159	 * nothing if !CONFIG_OF.
160	 */
161	if (mux_dev->of_node) {
162		struct device_node *child;
163		u32 reg;
164
165		for_each_child_of_node(mux_dev->of_node, child) {
166			ret = of_property_read_u32(child, "reg", &reg);
167			if (ret)
168				continue;
169			if (chan_id == reg) {
170				priv->adap.dev.of_node = child;
171				break;
172			}
173		}
174	}
175
176	if (force_nr) {
177		priv->adap.nr = force_nr;
178		ret = i2c_add_numbered_adapter(&priv->adap);
179	} else {
180		ret = i2c_add_adapter(&priv->adap);
181	}
182	if (ret < 0) {
183		dev_err(&parent->dev,
184			"failed to add mux-adapter (error=%d)\n",
185			ret);
186		kfree(priv);
187		return NULL;
188	}
189
190	WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"),
191			       "can't create symlink to mux device\n");
192
193	snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
194	WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name),
195			       "can't create symlink for channel %u\n", chan_id);
196	dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
197		 i2c_adapter_id(&priv->adap));
198
199	return &priv->adap;
200}
201EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
202
203void i2c_del_mux_adapter(struct i2c_adapter *adap)
204{
205	struct i2c_mux_priv *priv = adap->algo_data;
206	char symlink_name[20];
207
208	snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id);
209	sysfs_remove_link(&priv->mux_dev->kobj, symlink_name);
210
211	sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
212	i2c_del_adapter(adap);
213	kfree(priv);
214}
215EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
216
217MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
218MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
219MODULE_LICENSE("GPL v2");
220