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/*
* Multiplexed I2C bus driver.
*
* Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
* Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
* Copyright (c) 2009-2010 NSN GmbH & Co KG <michael.lawnick.ext@nsn.com>
*
* Simplifies access to complex multiplexed I2C bus topologies, by presenting
* each multiplexed bus segment as an additional I2C adapter.
* Supports multi-level mux'ing (mux behind a mux).
*
* Based on:
* i2c-virt.c from Kumar Gala <galak@kernel.crashing.org>
* i2c-virtual.c from Ken Harrenstien, Copyright (c) 2004 Google, Inc.
* i2c-virtual.c from Brian Kuschak <bkuschak@yahoo.com>
*
* This file is licensed under the terms of the GNU General Public
* License version 2. This program is licensed "as is" without any
* warranty of any kind, whether express or implied.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/i2c-mux.h>
#include <linux/of.h>
#include <linux/of_i2c.h>
/* multiplexer per channel data */
struct i2c_mux_priv {
struct i2c_adapter adap;
struct i2c_algorithm algo;
struct i2c_adapter *parent;
void *mux_priv; /* the mux chip/device */
u32 chan_id; /* the channel id */
int (*select)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
int (*deselect)(struct i2c_adapter *, void *mux_priv, u32 chan_id);
};
static int i2c_mux_master_xfer(struct i2c_adapter *adap,
struct i2c_msg msgs[], int num)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_adapter *parent = priv->parent;
int ret;
/* Switch to the right mux port and perform the transfer. */
ret = priv->select(parent, priv->mux_priv, priv->chan_id);
if (ret >= 0)
ret = parent->algo->master_xfer(parent, msgs, num);
if (priv->deselect)
priv->deselect(parent, priv->mux_priv, priv->chan_id);
return ret;
}
static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
u16 addr, unsigned short flags,
char read_write, u8 command,
int size, union i2c_smbus_data *data)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_adapter *parent = priv->parent;
int ret;
/* Select the right mux port and perform the transfer. */
ret = priv->select(parent, priv->mux_priv, priv->chan_id);
if (ret >= 0)
ret = parent->algo->smbus_xfer(parent, addr, flags,
read_write, command, size, data);
if (priv->deselect)
priv->deselect(parent, priv->mux_priv, priv->chan_id);
return ret;
}
/* Return the parent's functionality */
static u32 i2c_mux_functionality(struct i2c_adapter *adap)
{
struct i2c_mux_priv *priv = adap->algo_data;
struct i2c_adapter *parent = priv->parent;
return parent->algo->functionality(parent);
}
/* Return all parent classes, merged */
static unsigned int i2c_mux_parent_classes(struct i2c_adapter *parent)
{
unsigned int class = 0;
do {
class |= parent->class;
parent = i2c_parent_is_i2c_adapter(parent);
} while (parent);
return class;
}
struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
struct device *mux_dev,
void *mux_priv, u32 force_nr, u32 chan_id,
unsigned int class,
int (*select) (struct i2c_adapter *,
void *, u32),
int (*deselect) (struct i2c_adapter *,
void *, u32))
{
struct i2c_mux_priv *priv;
int ret;
priv = kzalloc(sizeof(struct i2c_mux_priv), GFP_KERNEL);
if (!priv)
return NULL;
/* Set up private adapter data */
priv->parent = parent;
priv->mux_priv = mux_priv;
priv->chan_id = chan_id;
priv->select = select;
priv->deselect = deselect;
/* Need to do algo dynamically because we don't know ahead
* of time what sort of physical adapter we'll be dealing with.
*/
if (parent->algo->master_xfer)
priv->algo.master_xfer = i2c_mux_master_xfer;
if (parent->algo->smbus_xfer)
priv->algo.smbus_xfer = i2c_mux_smbus_xfer;
priv->algo.functionality = i2c_mux_functionality;
/* Now fill out new adapter structure */
snprintf(priv->adap.name, sizeof(priv->adap.name),
"i2c-%d-mux (chan_id %d)", i2c_adapter_id(parent), chan_id);
priv->adap.owner = THIS_MODULE;
priv->adap.algo = &priv->algo;
priv->adap.algo_data = priv;
priv->adap.dev.parent = &parent->dev;
/* Sanity check on class */
if (i2c_mux_parent_classes(parent) & class)
dev_err(&parent->dev,
"Segment %d behind mux can't share classes with ancestors\n",
chan_id);
else
priv->adap.class = class;
/*
* Try to populate the mux adapter's of_node, expands to
* nothing if !CONFIG_OF.
*/
if (mux_dev->of_node) {
struct device_node *child;
u32 reg;
for_each_child_of_node(mux_dev->of_node, child) {
ret = of_property_read_u32(child, "reg", ®);
if (ret)
continue;
if (chan_id == reg) {
priv->adap.dev.of_node = child;
break;
}
}
}
if (force_nr) {
priv->adap.nr = force_nr;
ret = i2c_add_numbered_adapter(&priv->adap);
} else {
ret = i2c_add_adapter(&priv->adap);
}
if (ret < 0) {
dev_err(&parent->dev,
"failed to add mux-adapter (error=%d)\n",
ret);
kfree(priv);
return NULL;
}
dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
i2c_adapter_id(&priv->adap));
of_i2c_register_devices(&priv->adap);
return &priv->adap;
}
EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
int i2c_del_mux_adapter(struct i2c_adapter *adap)
{
struct i2c_mux_priv *priv = adap->algo_data;
i2c_del_adapter(adap);
kfree(priv);
return 0;
}
EXPORT_SYMBOL_GPL(i2c_del_mux_adapter);
MODULE_AUTHOR("Rodolfo Giometti <giometti@linux.it>");
MODULE_DESCRIPTION("I2C driver for multiplexed I2C busses");
MODULE_LICENSE("GPL v2");
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