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i2c: Multiplexed I2C bus core support 

Add multiplexed bus core support. I2C multiplexer and switches
like pca954x get instantiated as new adapters per port.

Signed-off-by: Michael Lawnick <ml.lawnick@gmx.de>
Acked-by: Rodolfo Giometti <giometti@linux.it>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
This commit is contained in:
Michael Lawnick 2010-08-11 18:21:02 +02:00 committed by Jean Delvare
parent dafc50d141
commit 0826374bff
7 changed files with 327 additions and 8 deletions
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11
drivers/i2c/Kconfig
View File

@ -47,6 +47,17 @@ config I2C_CHARDEV
This support is also available as a module. If so, the module
will be called i2c-dev.
config I2C_MUX
tristate "I2C bus multiplexing support"
depends on EXPERIMENTAL
help
Say Y here if you want the I2C core to support the ability to
handle multiplexed I2C bus topologies, by presenting each
multiplexed segment as a I2C adapter.
This support is also available as a module. If so, the module
will be called i2c-mux.
config I2C_HELPER_AUTO
bool "Autoselect pertinent helper modules"
default y

1
drivers/i2c/Makefile
View File

@ -6,6 +6,7 @@ obj-$(CONFIG_I2C_BOARDINFO) += i2c-boardinfo.o
obj-$(CONFIG_I2C) += i2c-core.o
obj-$(CONFIG_I2C_SMBUS) += i2c-smbus.o
obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o
obj-$(CONFIG_I2C_MUX) += i2c-mux.o
obj-y += algos/ busses/
ifeq ($(CONFIG_I2C_DEBUG_CORE),y)

58
drivers/i2c/i2c-core.c
View File

@ -20,7 +20,9 @@
/* With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi>.
All SMBus-related things are written by Frodo Looijaard <frodol@dds.nl>
SMBus 2.0 support by Mark Studebaker <mdsxyz123@yahoo.com> and
Jean Delvare <khali@linux-fr.org> */
Jean Delvare <khali@linux-fr.org>
Mux support by Rodolfo Giometti <giometti@enneenne.com> and
Michael Lawnick <michael.lawnick.ext@nsn.com> */
#include <linux/module.h>
#include <linux/kernel.h>
@ -423,10 +425,48 @@ static int __i2c_check_addr_busy(struct device *dev, void *addrp)
return 0;
}
/* walk up mux tree */
static int i2c_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
int result;
result = device_for_each_child(&adapter->dev, &addr,
__i2c_check_addr_busy);
if (!result && i2c_parent_is_i2c_adapter(adapter))
result = i2c_check_mux_parents(
to_i2c_adapter(adapter->dev.parent), addr);
return result;
}
/* recurse down mux tree */
static int i2c_check_mux_children(struct device *dev, void *addrp)
{
int result;
if (dev->type == &i2c_adapter_type)
result = device_for_each_child(dev, addrp,
i2c_check_mux_children);
else
result = __i2c_check_addr_busy(dev, addrp);
return result;
}
static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
{
return device_for_each_child(&adapter->dev, &addr,
__i2c_check_addr_busy);
int result = 0;
if (i2c_parent_is_i2c_adapter(adapter))
result = i2c_check_mux_parents(
to_i2c_adapter(adapter->dev.parent), addr);
if (!result)
result = device_for_each_child(&adapter->dev, &addr,
i2c_check_mux_children);
return result;
}
/**
@ -435,6 +475,9 @@ static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr)
*/
void i2c_lock_adapter(struct i2c_adapter *adapter)
{
if (i2c_parent_is_i2c_adapter(adapter))
i2c_lock_adapter(to_i2c_adapter(adapter->dev.parent));
else
rt_mutex_lock(&adapter->bus_lock);
}
EXPORT_SYMBOL_GPL(i2c_lock_adapter);
@ -445,6 +488,9 @@ EXPORT_SYMBOL_GPL(i2c_lock_adapter);
*/
static int i2c_trylock_adapter(struct i2c_adapter *adapter)
{
if (i2c_parent_is_i2c_adapter(adapter))
return i2c_trylock_adapter(to_i2c_adapter(adapter->dev.parent));
else
return rt_mutex_trylock(&adapter->bus_lock);
}
@ -454,6 +500,9 @@ static int i2c_trylock_adapter(struct i2c_adapter *adapter)
*/
void i2c_unlock_adapter(struct i2c_adapter *adapter)
{
if (i2c_parent_is_i2c_adapter(adapter))
i2c_unlock_adapter(to_i2c_adapter(adapter->dev.parent));
else
rt_mutex_unlock(&adapter->bus_lock);
}
EXPORT_SYMBOL_GPL(i2c_unlock_adapter);
@ -743,10 +792,11 @@ static const struct attribute_group *i2c_adapter_attr_groups[] = {
NULL
};
static struct device_type i2c_adapter_type = {
struct device_type i2c_adapter_type = {
.groups = i2c_adapter_attr_groups,
.release = i2c_adapter_dev_release,
};
EXPORT_SYMBOL_GPL(i2c_adapter_type);
#ifdef CONFIG_I2C_COMPAT
static struct class_compat *i2c_adapter_compat_class;

40
drivers/i2c/i2c-dev.c
View File

@ -189,12 +189,50 @@ static int i2cdev_check(struct device *dev, void *addrp)
return dev->driver ? -EBUSY : 0;
}
/* walk up mux tree */
static int i2cdev_check_mux_parents(struct i2c_adapter *adapter, int addr)
{
int result;
result = device_for_each_child(&adapter->dev, &addr, i2cdev_check);
if (!result && i2c_parent_is_i2c_adapter(adapter))
result = i2cdev_check_mux_parents(
to_i2c_adapter(adapter->dev.parent), addr);
return result;
}
/* recurse down mux tree */
static int i2cdev_check_mux_children(struct device *dev, void *addrp)
{
int result;
if (dev->type == &i2c_adapter_type)
result = device_for_each_child(dev, addrp,
i2cdev_check_mux_children);
else
result = i2cdev_check(dev, addrp);
return result;
}
/* This address checking function differs from the one in i2c-core
in that it considers an address with a registered device, but no
driver bound to it, as NOT busy. */
static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
{
return device_for_each_child(&adapter->dev, &addr, i2cdev_check);
int result = 0;
if (i2c_parent_is_i2c_adapter(adapter))
result = i2cdev_check_mux_parents(
to_i2c_adapter(adapter->dev.parent), addr);
if (!result)
result = device_for_each_child(&adapter->dev, &addr,
i2cdev_check_mux_children);
return result;
}
static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,

165
drivers/i2c/i2c-mux.c Normal file
View File

@ -0,0 +1,165 @@
/*
* 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>
/* multiplexer per channel data */
struct i2c_mux_priv {
struct i2c_adapter adap;
struct i2c_algorithm algo;
struct i2c_adapter *parent;
void *mux_dev; /* the mux chip/device */
u32 chan_id; /* the channel id */
int (*select)(struct i2c_adapter *, void *mux_dev, u32 chan_id);
int (*deselect)(struct i2c_adapter *, void *mux_dev, 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_dev, priv->chan_id);
if (ret >= 0)
ret = parent->algo->master_xfer(parent, msgs, num);
if (priv->deselect)
priv->deselect(parent, priv->mux_dev, 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_dev, 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_dev, 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);
}
struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
void *mux_dev, u32 force_nr, u32 chan_id,
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_dev = mux_dev;
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.id = parent->id;
priv->adap.algo = &priv->algo;
priv->adap.algo_data = priv;
priv->adap.dev.parent = &parent->dev;
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));
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;
int ret;
ret = i2c_del_adapter(adap);
if (ret < 0)
return ret;
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");

46
include/linux/i2c-mux.h Normal file
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@ -0,0 +1,46 @@
/*
*
* i2c-mux.h - functions for the i2c-bus mux support
*
* Copyright (c) 2008-2009 Rodolfo Giometti <giometti@linux.it>
* Copyright (c) 2008-2009 Eurotech S.p.A. <info@eurotech.it>
* Michael Lawnick <michael.lawnick.ext@nsn.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef _LINUX_I2C_MUX_H
#define _LINUX_I2C_MUX_H
#ifdef __KERNEL__
/*
* Called to create a i2c bus on a multiplexed bus segment.
* The mux_dev and chan_id parameters are passed to the select
* and deselect callback functions to perform hardware-specific
* mux control.
*/
struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
void *mux_dev, u32 force_nr, u32 chan_id,
int (*select) (struct i2c_adapter *,
void *mux_dev, u32 chan_id),
int (*deselect) (struct i2c_adapter *,
void *mux_dev, u32 chan_id));
int i2c_del_mux_adapter(struct i2c_adapter *adap);
#endif /* __KERNEL__ */
#endif /* _LINUX_I2C_MUX_H */

8
include/linux/i2c.h
View File

@ -37,6 +37,7 @@
#include <linux/of.h> /* for struct device_node */
extern struct bus_type i2c_bus_type;
extern struct device_type i2c_adapter_type;
/* --- General options ------------------------------------------------ */
@ -383,6 +384,13 @@ static inline void i2c_set_adapdata(struct i2c_adapter *dev, void *data)
dev_set_drvdata(&dev->dev, data);
}
static inline int i2c_parent_is_i2c_adapter(const struct i2c_adapter *adapter)
{
return adapter->dev.parent != NULL
&& adapter->dev.parent->bus == &i2c_bus_type
&& adapter->dev.parent->type == &i2c_adapter_type;
}
/* Adapter locking functions, exported for shared pin cases */
void i2c_lock_adapter(struct i2c_adapter *);
void i2c_unlock_adapter(struct i2c_adapter *);