i2c-mux-gpio: eliminate i2c channel order assumptions

The i2c-mux driver uses the chan_id parameter provided in i2c_add_mux_adapter as a parameter to the select and deselect callbacks while the i2c-mux-gpio driver uses the chan_id as an index in the mux->data.values array.

A simple example of where this doesn't work is when we have a device tree like this:

i2cmux {
	i2c@1 {
		reg = <1>;
		...
	};

	i2c@0 {
		reg = <0>;
		...
	};
};

The mux->data.values array will be { 1, 0 }, but when the i2-mux driver will try to select channel 0, the i2c-mux-gpio driver will actually use values[0], hence 1 as the gpio selection value.

Signed-off-by Ionut Nicu <[email protected]>

---
 drivers/i2c/muxes/i2c-mux-gpio.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

drivers/i2c/muxes/i2c-mux-gpio.c +2 -2

index b5f17ef..3505d0e 100644
@@ -43,7 +43,7 @@ static int i2c_mux_gpio_select(struct i2c_adapter *adap, void *data, u32 chan)
 {
 	struct gpiomux *mux = data;
 
-	i2c_mux_gpio_set(mux, mux->data.values[chan]);
+	i2c_mux_gpio_set(mux, chan);
 
 	return 0;
 }

@@ -233,7 +233,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
 		unsigned int class = mux->data.classes ? mux->data.classes[i] : 0;
 
 		mux->adap[i] = i2c_add_mux_adapter(parent, &pdev->dev, mux, nr,
-						   i, class,
+						   mux->data.values[i], class,
 						   i2c_mux_gpio_select, deselect);
 		if (!mux->adap[i]) {
 			ret = -ENODEV;

Hi!

Quoted 21 lines · Ionut Nicu

The i2c-mux driver uses the chan_id parameter provided in i2c_add_mux_adapter as a parameter to the select and deselect callbacks while the i2c-mux-gpio driver uses the chan_id as an index in the mux->data.values array.

A simple example of where this doesn't work is when we have a device tree like this:

i2cmux {
	i2c@1 {
		reg = <1>;
		...
	};

	i2c@0 {
		reg = <0>;
		...
	};
};

Quoted 4 lines

The mux->data.values array will be { 1, 0 }, but when the i2-mux driver will try to select channel 0, the i2c-mux-gpio driver will actually use values[0], hence 1 as the gpio selection value.

The patch itself is correct, but the description is not precise, I suppose... i2c-mux-gpio is consistent inside itself, it will receive for every child adapter the value it has configured. The problem happens inside i2c-mux.c, i2c_add_mux_adapter():

               	for_each_child_of_node(mux_dev->of_node, child) {
                       	ret = of_property_read_u32(child, "reg", &reg);
                       	if (ret)
                               	continue;
                       	if (chan_id == reg) {
                               	priv->adap.dev.of_node = child;

Which means, i2c-mux-gpio MUST pass reg, not its logical index inside array. Otherwise node will not be correctly assigned and i2c-mux will have problems selecting right adapter for the multiplexed devices.

Quoted 1 line

Signed-off-by Ionut Nicu <[email protected]>

So, for the code itself

Acked-by Alexander Sverdlin <[email protected]>

Quoted 27 lines

---
 drivers/i2c/muxes/i2c-mux-gpio.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

drivers/i2c/muxes/i2c-mux-gpio.c +2 -2

index b5f17ef..3505d0e 100644
@@ -43,7 +43,7 @@ static int i2c_mux_gpio_select(struct i2c_adapter *adap, void *data, u32 chan)
 {
 	struct gpiomux *mux = data;
 
-	i2c_mux_gpio_set(mux, mux->data.values[chan]);
+	i2c_mux_gpio_set(mux, chan);
 
 	return 0;
 }

@@ -233,7 +233,7 @@ static int i2c_mux_gpio_probe(struct platform_device *pdev)
 		unsigned int class = mux->data.classes ? mux->data.classes[i] : 0;
 
 		mux->adap[i] = i2c_add_mux_adapter(parent, &pdev->dev, mux, nr,
-						   i, class,
+						   mux->data.values[i], class,
 						   i2c_mux_gpio_select, deselect);
 		if (!mux->adap[i]) {
 			ret = -ENODEV;