Messages in this thread | | | Date | Mon, 02 Mar 2015 13:01:09 -0700 | From | Stephen Warren <> | Subject | Re: [PATCH v2 1/4] i2c: mux-pinctrl: Rework to honor disabled child nodes |
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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.
> diff --git a/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt b/Documentation/devicetree/bindings/i2c/i2c-mux-pinctrl.txt
> -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"?
> @@ -68,6 +68,7 @@ Example: > pinctrl-1 = <&state_i2cmux_pta>; > pinctrl-2 = <&state_i2cmux_idle>; > > + /* Enabled child bus 0 */ > i2c@0 { > reg = <0>; > #address-cells = <1>; > @@ -79,10 +80,12 @@ Example: > }; > }; > > + /* Disabled child bus 1 */ > i2c@1 { > reg = <1>; > #address-cells = <1>; > #size-cells = <0>; > + status = "disabled";
To make the example cover more cases, perhaps make child node i2c@0 disabled and i2c@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?
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