Re: [RFC v1] tree-wide: remove "select FW_LOADER" uses

[Josh Triplett <josh@joshtriplett.org>]

On Mon, May 25, 2015 at 07:07:14PM +0000, James Bottomley wrote:
> On Mon, 2015-05-25 at 10:54 -0700, Josh Triplett wrote:
> > On Mon, May 25, 2015 at 12:55:17PM +0200, Paul Bolle wrote:
> > > On Fri, 2015-05-22 at 14:43 -0700, josh@joshtriplett.org wrote:
> > > > Ideally, someone should teach Kconfig to handle recursive dependencies,
> > > 
> > > I'm probably reading too much in this remark, but how should it handle
> > > that other than returning an error because the configuration it's fed
> > > makes it run in circles?
> > 
> > I don't mean cyclic dependencies (for which Kconfig should just report
> > an error, ideally including the full list of symbols forming the cycle).
> > 
> > I mean that Kconfig should do recursive dependency resolution.  If B
> > depends on A, and C depends on B, I should be able to turn on C
> > directly and have B and A enabled.
> 
> That's really hard in practise you have to make any symbol that selects
> something depend on the dependencies of the selected symbol.  You can't
> do this without involving a SAT solver.  A guy promised to do this a
> couple of years ago, but the patches never materialised.  However, they
> may exist somewhere if someone wants to take a look at completing it.

You can't do this in the completely general case without a SAT solver.
However, I think it's possible to help the user a bit more than than
Kconfig currently does without introducing a general dependency solver.

In particular, it'd be nice to have an easy way to see at a glance
"can't enable C because it depends on B", together with an easy way to
get to B to enable it to get to C.  User-guided dependency resolution
seems like an improvement over no dependency resolution.

- Josh Triplett