Re: [gentoo-dev] Guidance on adding kernel config checks to ebuilds

[Mike Pagano]

On 9/27/21 12:10 PM, Mike Gilbert wrote:
> I'm looking to solicit opinions on when it is appropriate for an
> ebuild to check for kernel config options using linux-info.eclass. I
> don't think we have any guidelines documented, instead leaving it up
> to the "common sense" of package maintainers.
>
> Adding linux-info calls to pkg_pretend or pkg_setup causes slowdowns
> when running emerge, so we should do so only when there is a
> compensating benefit. It doesn't make sense to check for kernel
> options that are very commonly enabled. But what is "very common"?
>
> An obvious example would be CONFIG_INET, which controls IPv4 support
> in the kernel. It does not make sense to check for that in every
> package that uses AF_INET sockets.
>
> A less obvious example: a user filed a bug against net-misc/dhcpcd
> today asking that we check for CONFIG_PACKET [1]. My first thought was
> "why would you ever disable that?". The option description even says
> "if unsure, say Y". However, I suppose it is technically possible to
> run a Linux system with it disabled.
>
> I think a reasonable rule of thumb would be to assume we can rely on
> options that are enabled by "make defconfig". If the user chooses to
> disable them, they are responsible for anything that breaks.
>
> Thoughts?
>
> [1] https://bugs.gentoo.org/815064
>

The challenge I see is that these config checks head off bugs and issues without our intervention.

We as kernel maintainers depend on ebuild maintainers to check these things so they don't become "kernel bugs" to figure out.

> Adding linux-info calls to pkg_pretend or pkg_setup causes slowdowns
> when running emerge, so we should do so only when there is a
> compensating benefit.

Is this a significant slowdown? Do you have any numbers?