Re: [PATCH] [media] [kbuild] Add and use IS_REACHABLE macro
From: Michal Marek
Date: Thu Feb 19 2015 - 07:11:18 EST
On 2015-02-18 18:12, Arnd Bergmann wrote:
> In the media drivers, the v4l2 core knows about all submodules
> and calls into them from a common function. However this cannot
> work if the modules that get called are loadable and the
> core is built-in. In that case we get
> drivers/built-in.o: In function `set_type':
> drivers/media/v4l2-core/tuner-core.c:301: undefined reference to `tea5767_attach'
> drivers/media/v4l2-core/tuner-core.c:307: undefined reference to `tea5761_attach'
> drivers/media/v4l2-core/tuner-core.c:349: undefined reference to `tda9887_attach'
> drivers/media/v4l2-core/tuner-core.c:405: undefined reference to `xc4000_attach'
> Ideally Kconfig would be used to avoid the case of a broken dependency,
> or the code restructured in a way to turn around the dependency, but either
> way would require much larger changes here.
What can be done without extending kbuild is to accept
CONFIG_VIDEO_TUNER=y and CONFIG_MEDIA_TUNER_FOO=m, but build both into
the kernel, e.g.
diff --git a/drivers/media/tuners/Kconfig b/drivers/media/tuners/Kconfig
index 42e5a01..d2c7e89 100644
@@ -71,6 +71,11 @@ config MEDIA_TUNER_TEA5767
Say Y here to include support for the Philips TEA5767 radio tuner.
+ default VIDEO_TUNER || MEDIA_TUNER_TEA5767
+ depends on MEDIA_TUNER_TEA5767!=n
tristate "Mirics MSi001"
depends on MEDIA_SUPPORT && SPI && VIDEO_V4L2
Actually, I have hard time coming up with a kconfig syntactic sugar to
express such dependency. If I understand it correctly, the valid
configurations in this case are
MEDIA_TUNER_TEA5767 n m y
VIDEO_TUNER n x x x
m x x x
y x x
I.e. only VIDEO_TUNER=y and MEDIA_TUNER_TEA5767=m is incorrect, isn't
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