Pinmux with device tree

[Haojian Zhuang]

On Thu, May 19, 2011 at 3:33 AM, Mitch Bradley <wmb at firmworks.com> wrote:
> On 5/18/2011 6:34 AM, Simon Glass wrote:
>>
>> Hi,
>>
>> I see a new pinmux system in the LKML. Has anyone looked at how to
>> represent pinmux settings in the device tree?
>>
>> On a related topic, the examples that are used for GPIOs assume a
>> flags word which describes things like pull-ups, direction, etc. This
>> seems pretty cumbersome and gets worse with pinmuxes. People editing
>> the device trees want to see symbolic information rather than a coded
>> number, a bit like a #define. I can see this can be done with strings
>> but this is inefficient in time and space, and is error-prone.  Is
>> there support for this in device trees that I have missed?
>
> Open Firmware deals with this by defining both a numerical representation
> and a text representation.  The numerical representation appears in memory
> in device tree property values, and the corresponding text representation is
> for display and human input.
>
Could it be supported by flattened device tree? It seems that open firmware
isn't popular in ARM system.

> It primarily applies to unit addresses, i.e. the "reg" property value, but
> the idea generalizes.  The device tree compiler could accept the symbolic
> names, converting them into well-defined bitfield values which would be
> stored in integer cells within property values.
>
>
>