Documentation/kbuild: Document platform dependency practises
Document best practises for using architecture and platform dependencies. Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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@ -564,6 +564,30 @@ common system, and detect bugs that way.
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Note that compile-tested code should avoid crashing when run on a system where
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Note that compile-tested code should avoid crashing when run on a system where
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the dependency is not met.
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the dependency is not met.
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Architecture and platform dependencies
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Due to the presence of stubs, most drivers can now be compiled on most
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architectures. However, this does not mean it makes sense to have all drivers
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available everywhere, as the actual hardware may only exist on specific
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architectures and platforms. This is especially true for on-SoC IP cores,
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which may be limited to a specific vendor or SoC family.
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To prevent asking the user about drivers that cannot be used on the system(s)
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the user is compiling a kernel for, and if it makes sense, config symbols
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controlling the compilation of a driver should contain proper dependencies,
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limiting the visibility of the symbol to (a superset of) the platform(s) the
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driver can be used on. The dependency can be an architecture (e.g. ARM) or
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platform (e.g. ARCH_OMAP4) dependency. This makes life simpler not only for
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distro config owners, but also for every single developer or user who
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configures a kernel.
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Such a dependency can be relaxed by combining it with the compile-testing rule
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above, leading to:
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config FOO
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bool "Support for foo hardware"
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depends on ARCH_FOO_VENDOR || COMPILE_TEST
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Kconfig recursive dependency limitations
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Kconfig recursive dependency limitations
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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