On Monday 09 January 2012, Uwe Kleine-König wrote:

On Fri, Dec 23, 2011 at 09:44:28PM +0100, Uwe Kleine-König wrote:

quoted

On Fri, Dec 23, 2011 at 10:35:22AM +0000, Arnd Bergmann wrote:

quoted

On Thursday 22 December 2011, Uwe Kleine-König wrote:

quoted

[...]
+config SERIAL_EFM32_USART
+ bool "EFM32 USART port."
+ depends on ARCH_EFM32
+ select SERIAL_CORE

[...]

quoted

I would generally prefer not to make the driver depend on the
platform, so we can get better compile time coverage. I think a better
set of dependencies would be

    depends on HAVE_CLK
    depends on OF
    default ARCH_EFM32

I'd prefer something like:

      depends on HAVE_CLK
      depends on ARCH_EFM32 || I_DO_BUILD_COVERAGE_TESTING

This would make it easier for Joe User to pick the right options for his
kernel (assuming he found out to better keep I_DO_BUILD_COVERAGE_TESTING
disabled). [...]

What do you think about this I_DO_BUILD_COVERAGE_TESTING option? It
would allow testers to get all possible options enabled (though there
will never be an EFM32 USART port on a non-EFM32 machine I guess) and
still users and distribution packagers would easily keep the option off
even without cluttering .config and {menu,n,x,whatever}config.

Sorry for the late reply. The same topic has been discussed a lot of
times. We have different ways to handle this in the kernel, but the
way most common way is to use defconfig to decide which drivers to
use on a given machine but give the user the freedom to both enable
and disable any driver whereever possible, even if that would be
a silly thing to do. What we do require normally is that anything
that can be enabled is also able to be built without errors. A lot
of drivers have dependencies on platform specific header files
or other interfaces, so they require that platform to be enabled.

For all others I would not make such a restriction and I would always
recommend to be specific in the dependencies, e.g depending on HAVE_CLK
when you use the clock interfaces, instead of depending on other options
that implicitly enable HAVE_CLK.

	Arnd
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