[GIT PULL] On-demand device probing

[David Woodhouse]

On Mon, 2015-10-19 at 15:50 +0100, Mark Brown wrote:
> > But the point I'm making is that we are working towards *fixing* that,
> > and *not* using DT-specific code in places where we should be using the
> > generic APIs.
> 
> What is the plan for fixing things here?  It's not obvious (at least to
> me) that we don't want to have the subsystems having knowledge of how
> they are bound to a specific firmware which is what you seem to imply
> here. 

I don't know that there *is* a coherent plan here to address it all.

Certainly, we *will* need subsystems to have firmware-specific
knowledge in some cases. Take GPIO as an example; ACPI *has* a way to
describe GPIO, and properties which reference GPIO pins are intended to
work through that — while in DT, properties which reference GPIO pins
will have different contents. They'll be compatible at the driver
level, in the sense that there's a call to get a given GPIO given the
property name, but the subsystems *will* be doing different things
behind the scenes.

My plan, such as it is, is to go through the leaf-node drivers which
almost definitely *should* be firmware-agnostic, and convert those. And
then take stock of what we have left, and work out what, if anything,
still needs to be done.

> It seems like we're going to have to refactor these bits of code when
> they get generalised anyway so I'm not sure that the additional cost
> here is that big.

That's an acceptable answer — "we're adding legacy code here but we
know it's going to be refactored anyway". If that's true, all it takes
is a note in the commit comment to that effect. That's different from
having not thought about it :)

-- 
dwmw2

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