i2c-mux: Add support for device auto-detection

Let I2C bus segments behind multiplexers have a class. This allows for
device auto-detection on these segments. As long as parent segments
don't share the same class, it should be fine.

I implemented support in drivers i2c-mux-gpio and i2c-mux-pca954x. I
left i2c-mux-pca9541 and i2c-mux-pinctrl alone for the moment as I
don't know if this feature makes sense for the use cases of these
drivers.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Peter Korsgaard <peter.korsgaard@barco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: Michael Lawnick <ml.lawnick@gmx.de>
Cc: Rodolfo Giometti <giometti@linux.it>

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c
index 1038c38..d94e0ce 100644
--- a/drivers/i2c/i2c-mux.c
+++ b/drivers/i2c/i2c-mux.c
@@ -88,9 +88,23 @@ static u32 i2c_mux_functionality(struct i2c_adapter *adap)
 	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 *,
@@ -127,6 +141,14 @@ struct i2c_adapter *i2c_add_mux_adapter(struct i2c_adapter *parent,
 	priv->adap.algo_data = priv;
 	priv->adap.dev.parent = &parent->dev;
 
+	/* 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.