Re: [PATCH 1/4] kconfig: introduce the "imply" keyword

From	Josh Triplett <josh@joshtriplett.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 1/4] kconfig: introduce the "imply" keyword
Date	2016-10-20 17:50 +0200
Message-ID	<sunLs-12P-9@gated-at.bofh.it> (permalink)
References	<su8Mp-881-9@gated-at.bofh.it> <su8Mq-881-29@gated-at.bofh.it> <sumZ3-wo-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On Thu, Oct 20, 2016 at 03:52:04PM +0100, Edward Cree wrote:
> On 20/10/16 00:42, Nicolas Pitre wrote:
> > diff --git a/Documentation/kbuild/kconfig-language.txt b/Documentation/kbuild/kconfig-language.txt
> > index 069fcb3eef..c96127f648 100644
> > --- a/Documentation/kbuild/kconfig-language.txt
> > +++ b/Documentation/kbuild/kconfig-language.txt
> > @@ -113,6 +113,33 @@ applicable everywhere (see syntax).
> >       That will limit the usefulness but on the other hand avoid
> >       the illegal configurations all over.
> >
> > +- weak reverse dependencies: "imply" <symbol> ["if" <expr>]
> > +  This is similar to "select" as it enforces a lower limit on another
> > +  symbol except that the "implied" config symbol's value may still be
> > +  set to n from a direct dependency or with a visible prompt.
> > +  Given the following example:
> > +
> > +  config FOO
> > +     tristate
> > +     imply BAZ
> > +
> > +  config BAZ
> > +     tristate
> > +     depends on BAr
> > +
> > +  The following values are possible:
> > +
> > +     FOO             BAR             BAR's default   choice for BAZ
> Should the third column not be "BAZ's default"?
> > +     --------------- --------------- --------------- --------------
> > +     n               y               n               N/m/y
> > +     m               y               m               M/y/n
> > +     y               y               y               Y/n
> > +     y               n               *               N
> Also, I don't think having any FOO=y should preclude BAZ=m.  Suppose both
> FOO and FOO2 imply BAZ, FOO=y and FOO2=m.  Then if BAZ-features are only
> desired for driver FOO2, BAz=m makes sense.

That's exactly the problem that motivated "imply" in the first place:
while that's *possible*, it means the user needs to know that they're
breaking BAZ support for driver FOO.

In theory, someone could extend the UI to note the symbols with an
"imply" for a given symbol and provide additional help for the implied
symbol that explains the implications.  In that case, it might make
sense to allow the user to explicitly mark a symbol as 'm', with
appropriate explanations of the implications.  But in the absence of
that, the simple solution seems like preventing 'm' for a symbol implied
by a symbol marked as 'y'.

Thread

[PATCH 0/4] make POSIX timers optional with some Kconfig help Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 01:50 +0200
  [PATCH 3/4] ptp_clock: allow for it to be optional Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 01:50 +0200
    Re: [PATCH 3/4] ptp_clock: allow for it to be optional Thomas Gleixner <tglx@linutronix.de> - 2016-10-20 12:00 +0200
      Re: [PATCH 3/4] ptp_clock: allow for it to be optional Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 19:50 +0200
        Re: [PATCH 3/4] ptp_clock: allow for it to be optional Thomas Gleixner <tglx@linutronix.de> - 2016-10-20 20:10 +0200
    Re: [PATCH 3/4] ptp_clock: allow for it to be optional Richard Cochran <richardcochran@gmail.com> - 2016-10-20 16:10 +0200
      Re: [PATCH 3/4] ptp_clock: allow for it to be optional Josh Triplett <josh@joshtriplett.org> - 2016-10-20 17:50 +0200
      Re: [PATCH 3/4] ptp_clock: allow for it to be optional Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 18:50 +0200
  [PATCH 1/4] kconfig: introduce the "imply" keyword Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 01:50 +0200
    Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Masahiro Yamada <yamada.masahiro@socionext.com> - 2016-10-20 09:00 +0200
    Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Edward Cree <ecree@solarflare.com> - 2016-10-20 17:00 +0200
      Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Josh Triplett <josh@joshtriplett.org> - 2016-10-20 17:50 +0200
      Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 19:10 +0200
        Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Edward Cree <ecree@solarflare.com> - 2016-10-20 19:50 +0200
          Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 20:30 +0200
            Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Edward Cree <ecree@solarflare.com> - 2016-10-20 21:20 +0200
              Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 22:20 +0200
                Re: [PATCH 1/4] kconfig: introduce the "imply" keyword Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-21 05:30 +0200
  [PATCH 4/4] posix-timers: make it configurable Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 01:50 +0200
    Re: [PATCH 4/4] posix-timers: make it configurable Richard Cochran <richardcochran@gmail.com> - 2016-10-20 16:10 +0200
      Re: [PATCH 4/4] posix-timers: make it configurable Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 18:50 +0200
  Re: [PATCH 0/4] make POSIX timers optional with some Kconfig help Thomas Gleixner <tglx@linutronix.de> - 2016-10-20 11:50 +0200
    Re: [PATCH 0/4] make POSIX timers optional with some Kconfig help Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-10-20 20:40 +0200
  Re: [PATCH 0/4] make POSIX timers optional with some Kconfig help Josh Triplett <josh@joshtriplett.org> - 2016-10-20 21:00 +0200

csiph-web