[RFC PATCH 0/2] i2c/of: Populate multiplexed i2c busses from the device tree.

[RFC PATCH 0/2] i2c/of: Populate multiplexed i2c busses from the device tree.

[David Daney]

We need to populate our I2C devices from the device tree, but some of
our systems have multiplexers which currently break this process.

The basic idea is to have the generic i2c-mux framework propagate the
device_node for the child bus into the corresponding i2c_adapter, and
then call of_i2c_register_devices().  This means that the device tree
bindings for *all* i2c muxes must have some common properties.  I try
to document these in mux.txt.

At this point it is an RFC because the patches are against an old
kernel.  Once we agree on how this should look, I will test them
against a current kernel.

Any feedback on the approach and/or specific bindings is most welcome.

David Daney (2):
  i2c: Add a struct device * parameter to i2c_add_mux_adapter()
  i2c/of: Automatically populate i2c mux busses from device tree data.

 Documentation/devicetree/bindings/i2c/mux.txt |   54 +++++++++++++++++++++++++
 drivers/i2c/i2c-mux.c                         |   44 ++++++++++++++++----
 drivers/i2c/muxes/gpio-i2cmux.c               |    3 +-
 drivers/i2c/muxes/pca9541.c                   |    3 +-
 drivers/i2c/muxes/pca954x.c                   |    2 +-
 include/linux/i2c-mux.h                       |    3 +-
 6 files changed, 96 insertions(+), 13 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/i2c/mux.txt

-- 
1.7.2.3

[RFC PATCH 1/2] i2c: Add a struct device * parameter to i2c_add_mux_adapter()

[David Daney]

And adjust all callers.

The new device parameter is used in the next patch to initialize the
mux's of_node so that its children may be automatically populated.

Signed-off-by: David Daney <david.daney@cavium.com>
---
 drivers/i2c/i2c-mux.c           |   19 ++++++++++---------
 drivers/i2c/muxes/gpio-i2cmux.c |    3 ++-
 drivers/i2c/muxes/pca9541.c     |    3 ++-
 drivers/i2c/muxes/pca954x.c     |    2 +-
 include/linux/i2c-mux.h         |    3 ++-
 5 files changed, 17 insertions(+), 13 deletions(-)

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index d32a484..6fc2dd4 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -31,11 +31,11 @@ struct i2c_mux_priv {
 	struct i2c_algorithm algo;
 
 	struct i2c_adapter *parent;
-	void *mux_dev;	/* the mux chip/device */
+	void *mux_priv;	/* 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);
+	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,
@@ -47,11 +47,11 @@ static int i2c_mux_master_xfer(struct i2c_adapter *adap,
 
 	/* Switch to the right mux port and perform the transfer. */
 
-	ret = priv->select(parent, priv->mux_dev, priv->chan_id);
+	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_dev, priv->chan_id);
+		priv->deselect(parent, priv->mux_priv, priv->chan_id);
 
 	return ret;
 }
@@ -67,12 +67,12 @@ static int i2c_mux_smbus_xfer(struct i2c_adapter *adap,
 
 	/* Select the right mux port and perform the transfer. */
 
-	ret = priv->select(parent, priv->mux_dev, priv->chan_id);
+	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_dev, priv->chan_id);
+		priv->deselect(parent, priv->mux_priv, priv->chan_id);
 
 	return ret;
 }
@@ -87,7 +87,8 @@ static u32 i2c_mux_functionality(struct i2c_adapter *adap)
 }
 
 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
-				void *mux_dev, u32 force_nr, u32 chan_id,
+				struct device *mux_dev,
+				void *mux_priv, u32 force_nr, u32 chan_id,
 				int (*select) (struct i2c_adapter *,
 					       void *, u32),
 				int (*deselect) (struct i2c_adapter *,
@@ -102,7 +103,7 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
 
 	/* 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;
diff --git a/drivers/i2c/muxes/gpio-i2cmux.c b/drivers/i2c/muxes/gpio-i2cmux.c
index 7b6ce62..cd238c7 100644
--- a/drivers/i2c/muxes/gpio-i2cmux.c
+++ b/drivers/i2c/muxes/gpio-i2cmux.c
@@ -105,7 +105,8 @@ static int __devinit gpiomux_probe(struct platform_device *pdev)
 	for (i = 0; i < pdata->n_values; i++) {
 		u32 nr = pdata->base_nr ? (pdata->base_nr + i) : 0;
 
-		mux->adap[i] = i2c_add_mux_adapter(parent, mux, nr, i,
+		mux->adap[i] = i2c_add_mux_adapter(parent, &pdev->dev, mux,
+						   nr, i,
 						   gpiomux_select, deselect);
 		if (!mux->adap[i]) {
 			ret = -ENODEV;
diff --git a/drivers/i2c/muxes/pca9541.c b/drivers/i2c/muxes/pca9541.c
index ed699c5..e9e07ba 100644
--- a/drivers/i2c/muxes/pca9541.c
+++ b/drivers/i2c/muxes/pca9541.c
@@ -353,7 +353,8 @@ static int pca9541_probe(struct i2c_client *client,
 	force = 0;
 	if (pdata)
 		force = pdata->modes[0].adap_id;
-	data->mux_adap = i2c_add_mux_adapter(adap, client, force, 0,
+	data->mux_adap = i2c_add_mux_adapter(adap, &client->dev, client,
+					     force, 0,
 					     pca9541_select_chan,
 					     pca9541_release_chan);
 
diff --git a/drivers/i2c/muxes/pca954x.c b/drivers/i2c/muxes/pca954x.c
index 6f89536..5c6ecc7 100644
--- a/drivers/i2c/muxes/pca954x.c
+++ b/drivers/i2c/muxes/pca954x.c
@@ -226,7 +226,7 @@ static int pca954x_probe(struct i2c_client *client,
 		}
 
 		data->virt_adaps[num] =
-			i2c_add_mux_adapter(adap, client,
+			i2c_add_mux_adapter(adap, &client->dev, client,
 				force, num, pca954x_select_chan,
 				(pdata && pdata->modes[num].deselect_on_exit)
 					? pca954x_deselect_mux : NULL);
diff --git a/include/linux/i2c-mux.h b/include/linux/i2c-mux.h
index 34536ef..260ca6a 100644
--- a/include/linux/i2c-mux.h
+++ b/include/linux/i2c-mux.h
@@ -33,7 +33,8 @@
  * mux control.
  */
 struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
-				void *mux_dev, u32 force_nr, u32 chan_id,
+				struct device *mux_dev,
+				void *mux_priv, u32 force_nr, u32 chan_id,
 				int (*select) (struct i2c_adapter *,
 					       void *mux_dev, u32 chan_id),
 				int (*deselect) (struct i2c_adapter *,
-- 
1.7.2.3

[RFC PATCH 2/2] i2c/of: Automatically populate i2c mux busses from device tree data.

[David Daney]

For 'normal' i2c bus drivers, we can call of_i2c_register_devices()
and have the device tree framework automatically populate the bus with
the devices specified in the device tree.

This patch adds a common code to the i2c mux framework to hate the mux
sub-busses be populated by the of_i2c_register_devices() too.  If the
mux device has an of_node, we populate the sub-bus' of_node so that
the subsequent call to of_i2c_register_devices() will find the
corresponding devices.

It seemed better to put this logic in i2c_add_mux_adapter() rather
than the individual mux drivers, as they will all probably want to do
the same thing.

Signed-off-by: David Daney <david.daney@cavium.com>
---
 Documentation/devicetree/bindings/i2c/mux.txt |   54 +++++++++++++++++++++++++
 drivers/i2c/i2c-mux.c                         |   25 +++++++++++
 2 files changed, 79 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/i2c/mux.txt

diff --git a/Documentation/devicetree/bindings/i2c/mux.txt b/Documentation/devicetree/bindings/i2c/mux.txt
new file mode 100644
index 0000000..7bd9192
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/mux.txt
@@ -0,0 +1,54 @@
+Common i2c bus multiplexer/switch properties.
+
+An i2c bus multiplexer/switch will have several child busses that are
+numbered uniquely in a device dependent manner.  The nodes for an i2c bus
+multiplexer/switch will have one child node for each child
+bus.
+
+Required properties for child nodes:
+- #address-cells = <1>;
+- #size-cells = <0>;
+- cell-index : The sub-bus number.
+
+Optional properties for child nodes:
+- Other properties specific to the multiplexer/switch hardware.
+- Child nodes conforming to i2c bus binding
+
+
+Example :
+
+	/*
+	   An NXP pca9548 8 channel I2C multiplexer at address 0x70
+	   with two NXP pca8574 GPIO expanders attached, one each to
+	   ports 3 and 4.
+	 */
+
+	mux@70 {
+		compatible = "nxp,pca9548";
+		reg = <0x70>;
+
+		i2c@3 {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			cell-index = <3>;
+
+			gpio1: gpio@38 {
+				compatible = "nxp,pca8574";
+				reg = <0x38>;
+				#gpio-cells = <2>;
+				gpio-controller;
+			};
+		};
+		i2c@4 {
+			#address-cells = <1>;
+			#size-cells = <0>;
+			cell-index = <4>;
+
+			gpio2: gpio@38 {
+				compatible = "nxp,pca8574";
+				reg = <0x38>;
+				#gpio-cells = <2>;
+				gpio-controller;
+			};
+		};
+	};
diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 6fc2dd4..63f8989 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -24,6 +24,8 @@
 #include <linux/slab.h>
 #include <linux/i2c.h>
 #include <linux/i2c-mux.h>
+#include <linux/of.h>
+#include <linux/of_i2c.h>
 
 /* multiplexer per channel data */
 struct i2c_mux_priv {
@@ -143,6 +145,29 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
 	dev_info(&parent->dev, "Added multiplexed i2c bus %d\n",
 		 i2c_adapter_id(&priv->adap));
 
+#ifdef CONFIG_OF
+	/* Try to get populate the mux adapter's of_node */
+	if (mux_dev->of_node) {
+		struct device_node *child = NULL;
+		const __be32 *cell_index;
+		int len;
+
+		for (;;) {
+			child = of_get_next_child(mux_dev->of_node, child);
+			if (!child)
+				break;
+			cell_index = of_get_property(child, "cell-index", &len);
+			if (!cell_index || (len < sizeof(__be32)))
+				continue;
+			if (chan_id == be32_to_cpup(cell_index)) {
+				priv->adap.dev.of_node = child;
+				break;
+			}
+		}
+	}
+	of_i2c_register_devices(&priv->adap);
+#endif
+
 	return &priv->adap;
 }
 EXPORT_SYMBOL_GPL(i2c_add_mux_adapter);
-- 
1.7.2.3