2 * Multiplexed I2C bus driver.
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>
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).
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>
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.
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>
29 /* multiplexer per channel data */
31 struct i2c_adapter adap
;
32 struct i2c_algorithm algo
;
34 struct i2c_adapter
*parent
;
35 void *mux_priv
; /* the mux chip/device */
36 u32 chan_id
; /* the channel id */
38 int (*select
)(struct i2c_adapter
*, void *mux_priv
, u32 chan_id
);
39 int (*deselect
)(struct i2c_adapter
*, void *mux_priv
, u32 chan_id
);
42 static int i2c_mux_master_xfer(struct i2c_adapter
*adap
,
43 struct i2c_msg msgs
[], int num
)
45 struct i2c_mux_priv
*priv
= adap
->algo_data
;
46 struct i2c_adapter
*parent
= priv
->parent
;
49 /* Switch to the right mux port and perform the transfer. */
51 ret
= priv
->select(parent
, priv
->mux_priv
, priv
->chan_id
);
53 ret
= parent
->algo
->master_xfer(parent
, msgs
, num
);
55 priv
->deselect(parent
, priv
->mux_priv
, priv
->chan_id
);
60 static 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
)
65 struct i2c_mux_priv
*priv
= adap
->algo_data
;
66 struct i2c_adapter
*parent
= priv
->parent
;
69 /* Select the right mux port and perform the transfer. */
71 ret
= priv
->select(parent
, priv
->mux_priv
, priv
->chan_id
);
73 ret
= parent
->algo
->smbus_xfer(parent
, addr
, flags
,
74 read_write
, command
, size
, data
);
76 priv
->deselect(parent
, priv
->mux_priv
, priv
->chan_id
);
81 /* Return the parent's functionality */
82 static u32
i2c_mux_functionality(struct i2c_adapter
*adap
)
84 struct i2c_mux_priv
*priv
= adap
->algo_data
;
85 struct i2c_adapter
*parent
= priv
->parent
;
87 return parent
->algo
->functionality(parent
);
90 /* Return all parent classes, merged */
91 static unsigned int i2c_mux_parent_classes(struct i2c_adapter
*parent
)
93 unsigned int class = 0;
96 class |= parent
->class;
97 parent
= i2c_parent_is_i2c_adapter(parent
);
103 struct 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
,
107 int (*select
) (struct i2c_adapter
*,
109 int (*deselect
) (struct i2c_adapter
*,
112 struct i2c_mux_priv
*priv
;
113 char symlink_name
[20];
116 priv
= kzalloc(sizeof(struct i2c_mux_priv
), GFP_KERNEL
);
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
;
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.
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
;
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 priv
->adap
.retries
= parent
->retries
;
144 priv
->adap
.timeout
= parent
->timeout
;
146 /* Sanity check on class */
147 if (i2c_mux_parent_classes(parent
) & class)
148 dev_err(&parent
->dev
,
149 "Segment %d behind mux can't share classes with ancestors\n",
152 priv
->adap
.class = class;
155 * Try to populate the mux adapter's of_node, expands to
156 * nothing if !CONFIG_OF.
158 if (mux_dev
->of_node
) {
159 struct device_node
*child
;
162 for_each_child_of_node(mux_dev
->of_node
, child
) {
163 ret
= of_property_read_u32(child
, "reg", ®
);
166 if (chan_id
== reg
) {
167 priv
->adap
.dev
.of_node
= child
;
174 priv
->adap
.nr
= force_nr
;
175 ret
= i2c_add_numbered_adapter(&priv
->adap
);
177 ret
= i2c_add_adapter(&priv
->adap
);
180 dev_err(&parent
->dev
,
181 "failed to add mux-adapter (error=%d)\n",
187 WARN(sysfs_create_link(&priv
->adap
.dev
.kobj
, &mux_dev
->kobj
, "mux_device"),
188 "can't create symlink to mux device\n");
190 snprintf(symlink_name
, sizeof(symlink_name
), "channel-%u", chan_id
);
191 WARN(sysfs_create_link(&mux_dev
->kobj
, &priv
->adap
.dev
.kobj
, symlink_name
),
192 "can't create symlink for channel %u\n", chan_id
);
193 dev_info(&parent
->dev
, "Added multiplexed i2c bus %d\n",
194 i2c_adapter_id(&priv
->adap
));
198 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter
);
200 void i2c_del_mux_adapter(struct i2c_adapter
*adap
)
202 struct i2c_mux_priv
*priv
= adap
->algo_data
;
203 char symlink_name
[20];
205 snprintf(symlink_name
, sizeof(symlink_name
), "channel-%u", priv
->chan_id
);
206 sysfs_remove_link(&adap
->dev
.parent
->kobj
, symlink_name
);
208 sysfs_remove_link(&priv
->adap
.dev
.kobj
, "mux_device");
209 i2c_del_adapter(adap
);
212 EXPORT_SYMBOL_GPL(i2c_del_mux_adapter
);
214 MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
215 MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
216 MODULE_LICENSE("GPL v2");
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