Add to the I2C core the ability to handle multiplexed I2C bus topologies by presenting each multiplexed segment as a I2C adapter.
Signed-off-by: Rodolfo Giometti <[email protected]> --- drivers/i2c/Kconfig | 10 +++ drivers/i2c/Makefile | 3 +- drivers/i2c/i2c-mux.c | 180 ++++++++++++++++++++++++++++++++++++++++++++ drivers/i2c/muxes/Kconfig | 8 ++ drivers/i2c/muxes/Makefile | 6 ++ include/linux/i2c-id.h | 3 + include/linux/i2c.h | 14 ++++ 7 files changed, 223 insertions(+), 1 deletions(-) create mode 100644 drivers/i2c/i2c-mux.c create mode 100644 drivers/i2c/muxes/Kconfig create mode 100644 drivers/i2c/muxes/Makefile diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig index 711ca08..78dc245 100644 --- a/drivers/i2c/Kconfig +++ b/drivers/i2c/Kconfig @@ -27,6 +27,16 @@ config I2C_BOARDINFO boolean default y +config I2C_MUX + tristate "I2C bus multiplexing support" + depends on I2C + 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. + +source drivers/i2c/muxes/Kconfig + config I2C_CHARDEV tristate "I2C device interface" help diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile index ba26e6c..281e2a7 100644 --- a/drivers/i2c/Makefile +++ b/drivers/i2c/Makefile @@ -4,8 +4,9 @@ obj-$(CONFIG_I2C_BOARDINFO) += i2c-boardinfo.o obj-$(CONFIG_I2C) += i2c-core.o +obj-$(CONFIG_I2C_MUX) += i2c-mux.o obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o -obj-y += busses/ chips/ algos/ +obj-y += busses/ chips/ muxes/ algos/ ifeq ($(CONFIG_I2C_DEBUG_CORE),y) EXTRA_CFLAGS += -DDEBUG diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c new file mode 100644 index 0000000..390dbc3 --- /dev/null +++ b/drivers/i2c/i2c-mux.c @@ -0,0 +1,180 @@ +/* + * Multiplexed I2C bus driver. + * + * Copyright (c) 2008-2009 Rodolfo Giometti <[email protected]> + * Copyright (c) 2008-2009 Eurotech S.p.A. <[email protected]> + * + * Simplifies access to complex multiplexed I2C bus topologies, by presenting + * each multiplexed bus segment as a virtual I2C adapter. Supports multi-level + * mux'ing (mux behind a mux). + * + * Based on: + * i2c-virt.c from Kumar Gala <[email protected]> + * i2c-virtual.c from Copyright (c) 2004 Google, Inc. (Ken Harrenstien) + * i2c-virtual.c from Brian Kuschak <[email protected]> + * which was: + * Adapted from i2c-adap-ibm_ocp.c + * Original file Copyright 2000-2002 MontaVista Software Inc. + * + * 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/i2c.h> +#include <linux/i2c-id.h> + +struct i2c_mux_priv { + struct i2c_adapter adap; + struct i2c_algorithm algo; + + struct i2c_adapter *parent_adap; + void *client; /* The mux chip/device */ + u32 id; /* the mux id */ + + int (*select)(struct i2c_adapter *, void *, u32); + int (*deselect)(struct i2c_adapter *, void *, u32); +}; + +#define VIRT_TIMEOUT (HZ/2) +#define VIRT_RETRIES 3 + +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_adap; + int ret; + + /* Grab the lock for the parent adapter. We already hold the lock for + * the virtual adapter. Then select the right mux port and perform + * the transfer. + */ + + mutex_lock_nested(&parent->bus_lock, SINGLE_DEPTH_NESTING); + + ret = priv->select(parent, priv->client, priv->id); + if (ret >= 0) + ret = parent->algo->master_xfer(parent, msgs, num); + priv->deselect(parent, priv->client, priv->id); + + mutex_unlock(&parent->bus_lock); + + 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_adap; + int ret; + + /* Grab the lock for the parent adapter. We already hold the lock for + * the virtual adapter. Then select the right mux port and perform + * the transfer. + */ + + mutex_lock_nested(&parent->bus_lock, SINGLE_DEPTH_NESTING); + + ret = priv->select(parent, priv->client, priv->id); + if (ret == 0) + ret = parent->algo->smbus_xfer(parent, addr, flags, + read_write, command, size, data); + priv->deselect(parent, priv->client, priv->id); + + mutex_unlock(&parent->bus_lock); + + return ret; +} + +/* Return the parent's functionality for the virtual adapter */ +static u32 i2c_mux_functionality(struct i2c_adapter *adap) +{ + struct i2c_mux_priv *priv = adap->algo_data; + struct i2c_adapter *parent = priv->parent_adap; + + return parent->algo->functionality(parent); +} + +struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent, + void *client, u32 force_nr, u32 mux_val, + int (*select_cb) (struct i2c_adapter *, + void *, u32), + int (*deselect_cb) (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_adap = parent; + priv->client = client; + priv->id = mux_val; + priv->select = select_cb; + priv->deselect = deselect_cb; + + /* 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 (mux %02x)", + i2c_adapter_id(parent), mux_val); + priv->adap.owner = THIS_MODULE; + priv->adap.id = I2C_HW_VIRT | i2c_adapter_id(parent); + priv->adap.algo = &priv->algo; + priv->adap.algo_data = priv; + priv->adap.timeout = VIRT_TIMEOUT; + priv->adap.retries = VIRT_RETRIES; + 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) { + kfree(priv); + return NULL; + } + + dev_info(&parent->dev, "i2c-mux-%d: Virtual I2C bus - " + "physical bus i2c-%d, port %d\n", + i2c_adapter_id(&priv->adap), i2c_adapter_id(parent), mux_val); + + 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 <[email protected]>"); +MODULE_DESCRIPTION("Virtual I2C driver for multiplexed I2C busses"); +MODULE_LICENSE("GPL v2"); diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig new file mode 100644 index 0000000..95b9bde --- /dev/null +++ b/drivers/i2c/muxes/Kconfig @@ -0,0 +1,8 @@ +# +# Multiplexer I2C chip drivers configuration +# + +menu "Multiplexer I2C Chip support" + depends on I2C && I2C_MUX && EXPERIMENTAL + +endmenu diff --git a/drivers/i2c/muxes/Makefile b/drivers/i2c/muxes/Makefile new file mode 100644 index 0000000..5e70bde --- /dev/null +++ b/drivers/i2c/muxes/Makefile @@ -0,0 +1,6 @@ +# +# Makefile for multiplexer I2C chip drivers. + +ifeq ($(CONFIG_I2C_DEBUG_CHIP),y) +EXTRA_CFLAGS += -DDEBUG +endif diff --git a/include/linux/i2c-id.h b/include/linux/i2c-id.h index 01d67ba..d4f97b6 100644 --- a/include/linux/i2c-id.h +++ b/include/linux/i2c-id.h @@ -162,4 +162,7 @@ #define I2C_HW_SAA7146 0x060000 /* SAA7146 video decoder bus */ #define I2C_HW_SAA7134 0x090000 /* SAA7134 video decoder bus */ +/* --- Virtual adapter mark */ +#define I2C_HW_VIRT 0x80000000 + #endif /* LINUX_I2C_ID_H */ diff --git a/include/linux/i2c.h b/include/linux/i2c.h index 20873d4..748fc22 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -588,6 +588,20 @@ union i2c_smbus_data { #define I2C_SMBUS_BLOCK_PROC_CALL 7 /* SMBus 2.0 */ #define I2C_SMBUS_I2C_BLOCK_DATA 8 +/* + * Called to create a 'virtual' i2c bus which represents a multiplexed bus + * segment. The client and mux_val 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 *client, u32 force_nr, u32 mux_val, + int (*select_cb) (struct i2c_adapter *, + void *, u32), + int (*deselect_cb) (struct i2c_adapter *, + void *, u32)); + +int i2c_del_mux_adapter(struct i2c_adapter *adap); + #ifdef __KERNEL__ -- 1.5.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
