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    SubjectRe: [RFC][PATCH] kconfig: implement select with values
    Hi Sam,

    On Mon, Jul 26, 2010 at 4:17 PM, Sam Ravnborg <sam@ravnborg.org> wrote:
    > On Tue, Jul 20, 2010 at 04:37:06AM +1000, Stephen Rothwell wrote:
    >> This is a fairly brute force approach to allowing a Kconfig "select"
    >> to specify an excplicit value for the selected config sybmol.
    >>
    >> The syntax of select is changed to:
    >>
    >>       "select" <symbol> [<expr>] ["if" expr]
    >>
    >> The approach taken is to add a list of <value, dependency expression>
    >> pairs to the symbol and check them whenever the reverse depends (from
    >> a current-style select) are checked.
    >
    > I do not see the need for this feature.
    > I have read most of the postings in the defconfig battle and
    > I saw Linus' select suggestion.
    >
    > But we can do almost all of this today (or tomorrow).
    >
    > Consider following Kconfig file:
    >
    >    config USB_SUPPORT
    >            def_bool n
    >
    >    config NET
    >            def_bool y
    >
    >    source arch/x86/Kconfig
    >
    > We use the feature that we can specify the same
    > config option several times.
    > And the first default value that is "visible"
    > will be used.
    >
    > So it allows us to enable and disable any option.
    >
    > And if we for example want to set a specific LOG_BUF_SHIFT
    > we use the same trick:
    >
    >    config LOG_BUF_SHIFT
    >            int
    >            default 14

    Cute. I didn't know this was possible. I'll give it a try and see
    how it works for me. Do override config options also pickup
    select/depends constraints applied by later definitions? I think that
    would be necessary to kick out warnings when a defconfig selection
    isn't actually achievable.

    g.

    >
    >
    > Now in the original suggestion of Linus he used:
    >
    >    KBUILD_KCONFIG=Mykconfig make allnoconfig
    >
    > And "allnoconfig" would make the modified defaults useless.
    >
    > But the soon-to-be-introduced alldefconfig is more sensible.
    >
    > alldefconfig uses default values for everything.

    I basically used defconfig in the prototype that I posted. I think it
    works well for me, and I've got it integrated into the build targets
    (just like Stephen's earlier patch) without having to do a
    KBUILD_KCONFIG trick.

    g.

    --
    Grant Likely, B.Sc., P.Eng.
    Secret Lab Technologies Ltd.
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