GPIO - marking individual pins (not) available in device tree

[David Gibson]

On Thu, Oct 23, 2008 at 06:05:19PM -0500, Matt Sealey wrote:
>
>
> Mitch Bradley wrote:
> [snip]
>
>> You could adopt the convention that preassigned GPIOs must be  
>> represented by subordinate nodes, and any GPIO that is not covered by a 
>> subordinate node's "reg" property is implicitly available.  That's the  
>> way it works for other address spaces.

[snip]
> At the moment it's encoded as:
>
> 	gpios = <&controller-phandle pin-number pin-flags>

Actually, it's not.  The gpios property is:
	<controller-phandle gpio-descriptor ...>

The "gpio-descriptor" (like an interrupt descriptor from IEEE1275) is
a blob with number of cells equal to #gpio-cells from the controller.
The internal layout of the descriptor is specific to the gpio
controller.  Typically it includes a pin number and flags/mode.
However, it could be, and sometimes is, encoded as bank-number /
pin-number / flags.  Or even something more involved still, if that's
useful for the specific gpio controller in question.  Or it could
simply be pin number if it's associated with a really simple gpio
controller where all pins have the same behaviour.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
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