aboutsummaryrefslogtreecommitdiff
path: root/drivers/i2c/i2c-mux.c
diff options
context:
space:
mode:
authorMichael Lawnick <ml.lawnick@gmx.de>2010-08-11 18:21:02 +0200
committerJean Delvare <khali@linux-fr.org>2010-08-11 18:21:02 +0200
commit0826374bff57411d239f2fcb15da3c35af0a93cd (patch)
tree514d4361cfc9cc546306612de3464def7fe8a7cd /drivers/i2c/i2c-mux.c
parentdafc50d141c27959dbd3a1cfe9857a86d23402a7 (diff)
downloadlinux-linaro-stable-0826374bff57411d239f2fcb15da3c35af0a93cd.tar.gz
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>
Diffstat (limited to 'drivers/i2c/i2c-mux.c')
-rw-r--r--drivers/i2c/i2c-mux.c165
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");