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kbuild

Is it possible to convert a choice to an int in Kconfig

I'm looking for a way to convert a choice to an int in a Kconfig file. So for example, I would want:

config BUFSIZE
    int

choice
    prompt "choose a buffersize"
    depends on FOOBAR
    default 10 if FOO
    default 15 if BAR 
    default 20

config SIZE10
    bool "10"
    depends on !FOO
    select BUFSIZE=10

config SIZE15
    bool "15"
    depends on FOOBAR | BAR
    select BUFSIZE=15

config SIZE20
    bool "20"
    depends on BAR
    select BUFSIZE=20

endchoice

of course, you can't use = with select, so the above does not work. The actual list of choices is somewhat long and volatile, so I would like to avoid having a string of #ifdef's in another file to convert these to integers (plus these values are used in Makefiles as well as C files...)

My alternative is to make BUFSIZE user configurable, but that's problematic, as I cannot restrict the possible values very well. As well, if I specify a default value for an int, and run make oldconfig (where the value has not previously been defined), it prompts me for a value. If you set a default for a choice, it does not seem to prompt you on make oldconfig. This is important, as FOOBAR is turned off/on often, and I would like it to automatically select the default value for the architecture when it is turned on.

I'm wondering if there's a clean solution to this that I've overlooked.

Solution

  • Do it like this:

    choice
    prompt "choose a buffersize"
    depends on FOOBAR
    config BUFFERSIZE_15
        bool "15"
    config BUFFERSIZE_20
        bool "20"
    config BUFFERSIZE_25
        bool "25"
endchoice

config BUFSIZE
    int
    default 10
    default 15 if BUFFERSIZE_15
    default 20 if BUFFERSIZE_20
    default 25 if BUFFERSIZE_25