[RFC/PATCH 2/2] of: allow for boolean flags to have value

[Tony Lindgren]

* Mark Rutland <mark.rutland at arm.com> [150205 10:26]:
> On Thu, Feb 05, 2015 at 06:01:06PM +0000, Felipe Balbi wrote:
> > allowing values to boolean flags lets us setup
> > defaults on DTSI which can get disabled later
> > at board DTS if, for whatever reason, board can't
> > use that default.
> > 
> > One such example is DM81xx EVM where we can't use
> > MUSB's multipoint feature even though SoC supports
> > it. Something at the board level prevents us from
> > using the feature.
> > 
> > Instead of removing "multipoint;" from DTSI and
> > adding it to all board DTS just so we can remove
> > it from our quirky board seems like overkill when
> > we could just add:
> > 
> > 	multipoint = <0>;
> > 
> > to that quirky board's DTS.
> > 
> > Note that the description here is but one example
> > and it's likely many others have faced something
> > similar.
> > 
> 
> While I appreciate that adding and removing properties in this way is
> painful, I think that this must be dealt with at DTB compile-time rather
> than kernel run-time.
> 
> There are codebases other than Linux which parse DTs, and not all
> drivers call of_property_read_bool to parse boolean properties, an awful
> lot still just check of_find_property. Additionally, some bindings
> _explicitly_ state boolean properties are empty and have no value, which
> this extension would break.
> 
> I think that this patch only adds to the inconsistency we currently
> have, and given that, I would rather not have this extension to
> of_property_read_bool.
> 
> Arguably of_proeprty_read_bool should warn if it encounters a non-empty
> property.

How about a WARN_ON there as in that case the value will always
be set to 1 in kernel even if specified as 0 in the .dts file?

Regards,

Tony