Re: [PATCH] powerpc: Update all configs using savedefconfig

From: Geert Uytterhoeven
Date: Mon Feb 23 2015 - 04:59:51 EST

Hi Michael,

On Tue, Jan 20, 2015 at 8:05 AM, Michael Ellerman <mpe@xxxxxxxxxxxxxx> wrote:
> It looks like it's ~4 years since we updated some of these, so do a bulk
> update.
> Verified that the before and after generated configs are exactly the
> same.

Yep, that's guaranteed by the tool (modulo bugs).

> Which begs the question why update them? The answer is that it can be
> confusing when the stored defconfig drifts too far from the generated
> result.

And it becomes hard to update them, e.g. for enabling or disabling a single

Now the big question is: do they still work?
Plainly ignoring any bugs introduced in the code, there are probably several
"select" statements that have been removed. 4 years ago, they automatically
selected some critical options, while now, they're no longer selected, causing

I'm afraid the only safe way is (for all 108 defconfig files):
- start from the full .config file, as generated from the minimal defconfig
file in a source tree from 4 years ago,
- run "make oldconfig" (boring),
- run "make savedefconfig",
- update the minimal defconfig.

The boring step can be made a little bit less boring by making a diff between
the .config versions before and after running the first "make oldconfig",
and applying that to the later .config files first, but it's still a tedious
task, especially after 4 years. That's why I do this (for m68k) on every rc



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at