Re: [Buildroot] [RFC] Makefile: do defconfig with /dev/null instead of .defconfig

[Thomas Petazzoni via buildroot <buildroot@buildroot.org>]

On Sat, Oct 24, 2026 at 07:08:30PM +0200, Arnout Vandecappelle via buildroot wrote:
> For `make defconfig`, we use a .defconfig file. This is inherited from
> the kernel, which has a different defconfig for each architecture. The
> kernel defconfig passes ARCH on the command line rather than in Kconfig,
> and defaults are very different for different architectures. In
> Buildroot, we don't have that, instead we have a .defconfig file which
> only has the default architecture. And it's not actually a defconfig,
> it's a very old full .config where only the first part is kept.
> 
> Since we have architecture-independent defaults, and any architecture
> specific things are expressed with "depend on" and an occasional
> "default ... if ...", we don't need this infrastructure at all. We can
> simply make .defconfig an empty file - the BR2_arch choice has a default
> and that's all we need. And we don't even need an empty file, we have
> /dev/null to do that job.
> 
> Use /dev/null for the "defconfig" target if no DEFCONFIG is given.
> Remove the now unnecessary .defconfig.
> 
> Note that this also makes one hunk of
> support/kconfig/patches/01-kconfig-kernel-to-buildroot.patch redundant.
> Let's not do the effort of removing it now, we can remove it if it
> causes issues when updating the kconfig infrastructure.
> 
> Signed-off-by: Arnout Vandecappelle <arnout@rnout.be>

Tested-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Acked-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

(Since this is RFC, I'm not applying right away, just voicing my
approval for this change.)

Thomas
-- 
Thomas Petazzoni, co-owner and CEO, Bootlin
Embedded Linux and Kernel engineering and training
https://bootlin.com
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