From mboxrd@z Thu Jan 1 00:00:00 1970 From: Rodolfo Giometti Subject: [PATCH 1/3] i2c: virtual i2c adapter support. Date: Wed, 18 Jun 2008 15:06:03 +0200 Message-ID: <1213794365-8089-1-git-send-email-giometti@linux.it> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <> References: <> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: i2c-bounces-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org Errors-To: i2c-bounces-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org To: i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org Cc: Ben Dooks , Kumar Gala List-Id: linux-i2c@vger.kernel.org Simplifies access to complex multiplexed I2C bus topologies, by presenting each multiplexed bus segment as a virtual I2C adapter. In this manner I2C devices "after" the multiplexer can ba managed as usual. Signed-off-by: Rodolfo Giometti --- drivers/i2c/Kconfig | 9 +++ drivers/i2c/Makefile | 1 + drivers/i2c/i2c-virt.c | 188 ++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/i2c-id.h | 3 + include/linux/i2c.h | 17 +++++ 5 files changed, 218 insertions(+), 0 deletions(-) create mode 100644 drivers/i2c/i2c-virt.c diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig index 9686734..053fe2f 100644 --- a/drivers/i2c/Kconfig +++ b/drivers/i2c/Kconfig @@ -27,6 +27,15 @@ config I2C_BOARDINFO boolean default y +config I2C_VIRT + tristate "I2C virtual adapter support" + depends on I2C + help + Say Y here if you want the I2C core to support the ability to have + virtual adapters. Virtual adapters are useful to handle multiplexed + I2C bus topologies, by presenting each multiplexed segment as a + I2C adapter. + config I2C_CHARDEV tristate "I2C device interface" help diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile index ba26e6c..db72ed9 100644 --- a/drivers/i2c/Makefile +++ b/drivers/i2c/Makefile @@ -4,6 +4,7 @@ obj-$(CONFIG_I2C_BOARDINFO) += i2c-boardinfo.o obj-$(CONFIG_I2C) += i2c-core.o +obj-$(CONFIG_I2C_VIRT) += i2c-virt.o obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o obj-y += busses/ chips/ algos/ diff --git a/drivers/i2c/i2c-virt.c b/drivers/i2c/i2c-virt.c new file mode 100644 index 0000000..ed58f64 --- /dev/null +++ b/drivers/i2c/i2c-virt.c @@ -0,0 +1,188 @@ +/* + * i2c-virt.c - Virtual I2C bus driver. + * + * Copyright (c) 2008 Rodolfo Giometti + * Copyright (c) 2008 Eurotech S.p.A. + * + * 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 + * i2c-virtual.c from Copyright (c) 2004 Google, Inc. (Ken Harrenstien) + * i2c-virtual.c from Brian Kuschak + * 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 +#include +#include +#include + +struct i2c_virt_priv { + struct i2c_adapter *parent_adap; + struct i2c_client *client; /* The mux chip/device */ + + u32 id; /* the mux id */ + + int (*select)(struct i2c_adapter *, struct i2c_client *, u32); + /* Enable the mux */ + int (*deselect)(struct i2c_adapter *, struct i2c_client *, u32); + /* Disable the mux */ +}; + +#define VIRT_TIMEOUT (HZ/2) +#define VIRT_RETRIES 3 + +static int i2c_virt_master_xfer(struct i2c_adapter *adap, + struct i2c_msg msgs[], int num) +{ + struct i2c_virt_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(&parent->bus_lock); + + 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_virt_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_virt_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(&parent->bus_lock); + + 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_virt_functionality(struct i2c_adapter *adap) +{ + struct i2c_virt_priv *priv = adap->algo_data; + struct i2c_adapter *parent = priv->parent_adap; + + return parent->algo->functionality(parent); +} + +struct i2c_adapter *i2c_add_virt_adapter(struct i2c_adapter *parent, + struct i2c_client *client, + u32 force_nr, u32 mux_val, + int (*select_cb) (struct i2c_adapter *, + struct i2c_client *, u32), + int (*deselect_cb) (struct i2c_adapter *, + struct i2c_client *, u32)) +{ + struct i2c_adapter *adap; + struct i2c_virt_priv *priv; + struct i2c_algorithm *algo; + int ret; + + adap = kzalloc(sizeof(struct i2c_adapter) + + sizeof(struct i2c_virt_priv) + + sizeof(struct i2c_algorithm), GFP_KERNEL); + if (!adap) + return NULL; + + priv = (struct i2c_virt_priv *)(adap + 1); + algo = (struct i2c_algorithm *)(priv + 1); + + /* 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. + */ + algo->master_xfer = (parent->algo->master_xfer + ? i2c_virt_master_xfer : NULL); + algo->smbus_xfer = (parent->algo->smbus_xfer + ? i2c_virt_smbus_xfer : NULL); + algo->functionality = i2c_virt_functionality; + + /* Now fill out new adapter structure */ + snprintf(adap->name, sizeof(adap->name), + "i2c-%d-virt (mux %02x:%02x)", + i2c_adapter_id(parent), client->addr, mux_val); + adap->id = I2C_HW_VIRT | i2c_adapter_id(parent); + adap->algo = algo; + adap->algo_data = priv; + adap->timeout = VIRT_TIMEOUT; + adap->retries = VIRT_RETRIES; + adap->dev.parent = &parent->dev; + + if (force_nr) { + adap->nr = force_nr; + ret = i2c_add_numbered_adapter(adap); + } else + ret = i2c_add_adapter(adap); + if (ret < 0) { + kfree(adap); + return NULL; + } + + dev_info(&parent->dev, "i2c-virt-%d: Virtual I2C bus - " + "physical bus i2c-%d, multiplexer 0x%02x port %d\n", + i2c_adapter_id(adap), i2c_adapter_id(parent), + client->addr, mux_val); + + return adap; +} +EXPORT_SYMBOL_GPL(i2c_add_virt_adapter); + +int i2c_del_virt_adapter(struct i2c_adapter *adap) +{ + int ret; + + ret = i2c_del_adapter(adap); + if (ret < 0) + return ret; + kfree(adap); + + return 0; +} +EXPORT_SYMBOL_GPL(i2c_del_virt_adapter); + +MODULE_AUTHOR("Rodolfo Giometti "); +MODULE_DESCRIPTION("Virtual I2C driver for multiplexed I2C busses"); +MODULE_LICENSE("GPL"); diff --git a/include/linux/i2c-id.h b/include/linux/i2c-id.h index 580acc9..ba19ef9 100644 --- a/include/linux/i2c-id.h +++ b/include/linux/i2c-id.h @@ -176,4 +176,7 @@ #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 fb9af6a..968e8f3 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -553,6 +553,23 @@ 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. + * + * The caller is expected to have the core_lists lock + */ +struct i2c_adapter *i2c_add_virt_adapter(struct i2c_adapter *parent, + struct i2c_client *client, + u32 force_nr, u32 mux_val, + int (*select_cb) (struct i2c_adapter *, + struct i2c_client *, u32), + int (*deselect_cb) (struct i2c_adapter *, + struct i2c_client *, u32)); + +int i2c_del_virt_adapter(struct i2c_adapter *adap); + #ifdef __KERNEL__ -- 1.5.4.3 _______________________________________________ i2c mailing list i2c-GZX6beZjE8VD60Wz+7aTrA@public.gmane.org http://lists.lm-sensors.org/mailman/listinfo/i2c