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