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>

1 files changed, 165 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
new file mode 100644
index 000000000000..d32a4843fc3a
--- /dev/null
+++ b/drivers/i2c/i2c-mux.c
@@ -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");