Include TMPFS in all the GENERIC kernel configs

[arichardson]

Summary

Being able to use tmpfs without kernel modules is very useful when building
small MFS_ROOT kernels without a real file system.
Including TMPFS also matches arm/GENERIC and the MIPS std.MALTA configs.

Compiling TMPFS only adds 4 .c files so this should not make much of a
difference to NO_MODULES build times (as we do for our minimal RISC-V
images).

Test Plan

I can now create /tmp as a tmpfs mount on a kernel without modules.

[jrtc27]

Why are we doing this for GENERIC? No other architecture does so, and the only differences between them for GENERIC should be genuinely architecture-specific things, which TMPFS is not. If you want it for MFSROOT kernels, limit it to those. GENERIC is supposed to pick it up as a module just like everything else not required during earlyish boot.

[arichardson]

In D25317#558618, @jrtc27 wrote:

Why are we doing this for GENERIC? No other architecture does so, and the only differences between them for GENERIC should be genuinely architecture-specific things, which TMPFS is not. If you want it for MFSROOT kernels, limit it to those. GENERIC is supposed to pick it up as a module just like everything else not required during earlyish boot.

arm/GENERIC has include "std.armv7" which enables TMPFS

[jrtc27]

In D25317#558621, @arichardson wrote:

In D25317#558618, @jrtc27 wrote:

Why are we doing this for GENERIC? No other architecture does so, and the only differences between them for GENERIC should be genuinely architecture-specific things, which TMPFS is not. If you want it for MFSROOT kernels, limit it to those. GENERIC is supposed to pick it up as a module just like everything else not required during earlyish boot.

arm/GENERIC has include "std.armv7" which enables TMPFS

True, and perhaps for similar reasons of being used on (somewhat-)embedded devices. Honestly I don't know why it _isn't_ always compiled in.

[arichardson]

In D25317#559146, @jrtc27 wrote:

In D25317#558621, @arichardson wrote:

In D25317#558618, @jrtc27 wrote:

Why are we doing this for GENERIC? No other architecture does so, and the only differences between them for GENERIC should be genuinely architecture-specific things, which TMPFS is not. If you want it for MFSROOT kernels, limit it to those. GENERIC is supposed to pick it up as a module just like everything else not required during earlyish boot.

arm/GENERIC has include "std.armv7" which enables TMPFS

True, and perhaps for similar reasons of being used on (somewhat-)embedded devices. Honestly I don't know why it _isn't_ always compiled in.

Yeah it's like 3 .c files. I can try adding it to the other GENERIC kernels, but I'm not sure who to add to that review.

[arichardson]

Add TMPFS to all kernel configs instead

[arichardson]

ping?

[emaste]

SGTM