[yocto] Package Feature compile/runtime dependency

[Koehler, Yannick (HP Networking)]

I played with the system yesterday and find Yocto to be great.  Being a Gentoo user, I love the approach taken and see lots of enhancements made.  The biggest one is that fact that some packages, like the kernel and glibc got break down in a set of feature that can be better controlled than manually setting their configuration.  But, this added flexibility create a new level of inter-dependencies, which I think Yocto would gain to add support for.  Here is an example, if I add system to poky-tiny, it won't compile, and once I fix that, it won't boot.  The reason is that systemd package depends not only on other user-space package, but also on kernel features as well as glibc feature just to compile.  There is also other dependency at runtime for certain functionality as well.

Yocto already has a package dependency mechanism with DEPEND and RDEPEND, it would be great if we could somehow tie this with feature as well:

	DEPENDS="package:feature"
	RDEPENDS="package:feature"

This would allow to provide better error indication to the Yocto end-user when playing with distro/image and new combination. I could see system dependency added like this:

 	DEPENDS="linux-yocto-tiny:fhandle,autofs4,ipv6?,devtmpfs,libc:ftraverse,posix-clang-wchar,spawn,utmpx"

Etc...  Disregard the syntax as it is simply an idea/example and not intended as a specification.

Anyway, I am just sharing because I feel this system is really well done, and see this as an opportunity to get it to another level.

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Yannick Koehler