Subject: Re: linux-next: build failure after merge of the final tree (pwm tree related)

From: Thierry Reding <[email-masked]>
Date: Sun, 1 Jul 2012 08:56:39 +0200

On Sat, Jun 30, 2012 at 08:12:32PM +0000, Arnd Bergmann wrote:
> On Saturday 30 June 2012, Thierry Reding wrote:
> > > I think that all the drivers that are not converted to the common PWM
> > > layer yet should depend on not enabling the common code. Once they
> > > are all moved over, that dependency will go away.
> > 
> > Right. That's exactly what I meant. If we add depends on !HAVE_PWM to
> > the PWM symbol that should result in both options conflicting, and
> > therefore not being built at the same time.
> 
> But I would add it to all other ones then, not the generic one!

But if we make the new PWM symbol conflict with HAVE_PWM, then it'll do
the right thing for any of the legacy PWM implementations, without
having to track them down. Furthermore it'll also keep the legacy
version by default and not allow the generic one to be enabled in that
case. This is more likely to cause less side-effects than the other way
around.

> One question though: if the generic pwm implementation does not set
> HAVE_PWM, how can a driver check its presence?

The driver depends on PWM. HAVE_PWM is the symbol for the legacy
implementations, while PWM is the new PWM API symbol.

Thierry