linux-kernel - Re: [PATCH] kconfig: untangle EXPERT and EMBEDDED

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Message-ID: <20120117082842.GA3188@turtle.usersys.redhat.com>
Date:	Tue, 17 Jan 2012 09:28:43 +0100
From:	Andrew Jones <drjones@...hat.com>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	Jerome Marchand <jmarchan@...hat.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, rientjes@...gle.com, mingo@...e.hu,
	david.woodhouse@...el.com, gregkh@...e.de, davem@...emloft.net,
	axboe@...nel.dk, arnd@...db.de, holt@....com,
	linux-arch@...r.kernel.org, linux@....linux.org.uk,
	hskinnemoen@...il.com, egtvedt@...fundet.no, msalter@...hat.com,
	a-jacquiot@...com, starvik@...s.com, jesper.nilsson@...s.com,
	dhowells@...hat.com, takata@...ux-m32r.org,
	yasutake.koichi@...panasonic.com, jonas@...thpole.se,
	kyle@...artin.ca, deller@....de, jejb@...isc-linux.org,
	chris@...kel.net, greg@...ah.com, davej@...hat.com,
	airlied@...ux.ie, jkosina@...e.cz, mchehab@...radead.org,
	johannes@...solutions.net, linville@...driver.com
Subject: Re: [PATCH] kconfig: untangle EXPERT and EMBEDDED

On Mon, Jan 16, 2012 at 06:34:44PM +0100, Geert Uytterhoeven wrote:
> On Mon, Jan 16, 2012 at 16:50, Andrew Jones <drjones@...hat.com> wrote:
> > On Mon, Jan 16, 2012 at 04:40:47PM +0100, Jerome Marchand wrote:
> >> > @@ -1259,8 +1259,7 @@ config SLUB
> >> >        a slab allocator.
> >> >
> >> >  config SLOB
> >> > -   depends on EXPERT
> >> > -   bool "SLOB (Simple Allocator)"
> >> > +   bool "SLOB (Simple Allocator)" if EXPERT
> >> >     help
> >> >        SLOB replaces the stock allocator with a drastically simpler
> >> >        allocator. SLOB is generally more space efficient but
> >>
> >> Am I missing something or this particular chunk does not actually change
> >> anything?
> >
> > No, you're correct. There's no actual change, so the hunk could be dubbed
> > as an unnecessary cleanup. I made the change in order to give it the same
> > general format as the rest of the expert options in that file.
> 
> There _is_ a difference:
>   - "depends on EXPERT" means the option cannot be enabled by the user.
>     "select SLOB" will still override that, but kconf will print a warning.
>   - "bool ... if EXPERT" means the question will only be asked if EXPERT.
>     Other Kconfig logic can still "select SLOB" if it wants to.
>

No, they are equivalent. It says in the documentation
(Documentation/kbuild/kconfig-language.txt)

    - dependencies: "depends on" <expr>
      This defines a dependency for this menu entry. If multiple
      dependencies are defined, they are connected with '&&'. Dependencies
      are applied to all other options within this menu entry (which also
      accept an "if" expression), so these two examples are equivalent:

            bool "foo" if BAR
            default y if BAR
      and
            depends on BAR
            bool "foo"
            default y

SLOB doesn't have a default option in its entry (it actually can't, since
it's a choice value), or any other option type besides help, so the change
in the patch above is precisely equivalent.

If you got a warning with one style, but not the other, then that would be
a bug with kconf. However, I just tried to generate a warning with both
styles and couldn't.

Drew
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