On 02/27/2015 05:24 AM, Sebastian Hesselbarth wrote:

I2C mux pinctrl driver currently determines the number of sub-busses by
counting available pinctrl-names. Unfortunately, this requires each
incarnation of the devicetree node with different available sub-busses
to be rewritten.

This patch reworks i2c-mux-pinctrl driver to count the number of
available sub-nodes instead. The rework should be compatible to the old
way of probing for sub-busses and additionally allows to disable unused
sub-busses with standard DT property status = "disabled".

This also amends the corresponding devicetree binding documentation to
reflect the new functionality to disable unused sub-nodes. While at it,
also fix two references to binding documentation files that miss an "i2c-"
prefix.

-For each named state defined in the pinctrl-names property, an I2C child bus
-will be created. I2C child bus numbers are assigned based on the index into
-the pinctrl-names property.
+For each enabled child node an I2C child bus will be created. I2C child bus
+numbers are assigned based on the order of child nodes.

I think that I2C bus numbers are an internal concept for the OS. As 
such, we should probably remove any mention re: the bus numbers from the 
binding.

-The only exception is that no bus will be created for a state named "idle". If
-such a state is defined, it must be the last entry in pinctrl-names. For
-example:
+There must be a corresponding pinctrl-names entry for each enabled child
+node at the position of the child node's "reg" property. Also, there can be
+an idle pinctrl state defined at the end of possible pinctrl states. If such
+a state is defined, it must be the last entry in pinctrl-names. For example:

What about gaps in the numbering sequence? IIRC, in a situation with 5 
nodes with reg 0, 1, 2, 3, 4 but where only the nodes with reg of 1, 3 
enabled, we only want 2 entries in pinctrl-names? If so, "at the 
position of the child node's "reg" property" isn't correct, since "at 
the position" implies there must be gaps in pinctrl-names. "In the same 
order as the reg property values for enabled subnodes" might be a better 
description.

Perhaps I'm misremembering and you explicitly didn't want to remove 
entries from pinctrl-names if child nodes were disabled? If so, then 
surely then in the text above, "for each enabled child" should be 
replaced with "for each child"?

To make the example cover more cases, perhaps make child node i2c at 0 
disabled and i2c at 1 enabled. Then, the example would show what happens to 
pinctrl-names when there are gaps in the reg property numbering space of 
enabled children?