--- /dev/null
+/*
+ * 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>
+
+/* multiplexer per channel data */
+struct i2c_mux_priv {
+ struct i2c_adapter adap;
+ struct i2c_algorithm algo;
+
+ struct i2c_adapter *parent;
+ struct device *mux_dev;
+ void *mux_priv;
+ u32 chan_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;
+ char symlink_name[20];
+ 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->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;
+ priv->adap.retries = parent->retries;
+ priv->adap.timeout = parent->timeout;
+
+ /* 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;
+ }
+
+ WARN(sysfs_create_link(&priv->adap.dev.kobj, &mux_dev->kobj, "mux_device"),
+ "can't create symlink to mux device\n");
+
+ snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
+ WARN(sysfs_create_link(&mux_dev->kobj, &priv->adap.dev.kobj, symlink_name),
+ "can't create symlink for channel %u\n", chan_id);
+ 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);
+
+void i2c_del_mux_adapter(struct i2c_adapter *adap)
+{
+ struct i2c_mux_priv *priv = adap->algo_data;
+ char symlink_name[20];
+
+ snprintf(symlink_name, sizeof(symlink_name), "channel-%u", priv->chan_id);
+ sysfs_remove_link(&priv->mux_dev->kobj, symlink_name);
+
+ sysfs_remove_link(&priv->adap.dev.kobj, "mux_device");
+ i2c_del_adapter(adap);
+ kfree(priv);
+}
+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");
Code Review / kvmfornfv.git / blobdiff