linux-kernel - Re: [PATCH 1/2] kbuild: Enable decompression for use by EXTRA_FIRMWARE The build system can currently only compress files. This patch adds the functionality to decompress files. Decompression is needed for building firmware files into the kernel if those files are compressed on the filesystem. Compressed firmware files are in use by Gentoo, Fedora, Arch, and others.

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Date: Wed, 3 Jan 2024 21:00:29 +0900
From: Masahiro Yamada <masahiroy@...nel.org>
To: Kevin Martin <kevinmbecause@...il.com>
Cc: joeyzerocrash@...tonmail.com, Nathan Chancellor <nathan@...nel.org>, 
	Nick Desaulniers <ndesaulniers@...gle.com>, Nicolas Schier <nicolas@...sle.eu>, 
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] kbuild: Enable decompression for use by
 EXTRA_FIRMWARE The build system can currently only compress files. This patch
 adds the functionality to decompress files. Decompression is needed for
 building firmware files into the kernel if those files are compressed on the
 filesystem. Compressed firmware files are in use by Gentoo, Fedora, Arch, and others.

On Wed, Dec 20, 2023 at 7:26 PM Kevin Martin <kevinmbecause@...il.com> wrote:
>
> Signed-off-by: Kevin Martin <kevinmbecause@...il.com>
> ---
>  scripts/Makefile.lib | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> index 1a965fe68..d043be3dc 100644
> --- a/scripts/Makefile.lib
> +++ b/scripts/Makefile.lib
> @@ -523,6 +523,9 @@ quiet_cmd_xzkern_with_size = XZKERN  $@
>  quiet_cmd_xzmisc = XZMISC  $@
>        cmd_xzmisc = cat $(real-prereqs) | $(XZ) --check=crc32 --lzma2=dict=1MiB > $@
>
> +quiet_cmd_xzdec = XZDEC   $@
> +      cmd_xzdec = cat $(real-prereqs) | $(XZ) --decompress > $@
> +



Please do not fork the meaningless 'cat' process.

This should be a single process to take just one input file.

    cmd_xzdec = $(XZ) --decompress --stdout $< > $@




Commit d3dd3b5a29bb9582957451531fed461628dfc834
was a very bad commit.

The 'cat' and compression/decompression must be
separate rules.

We should not repeat the mistake in the past.



>  # ZSTD
>  # ---------------------------------------------------------------------------
>  # Appends the uncompressed size of the data using size_append. The .zst
> @@ -548,6 +551,9 @@ quiet_cmd_zstd22 = ZSTD22  $@
>  quiet_cmd_zstd22_with_size = ZSTD22  $@
>        cmd_zstd22_with_size = { cat $(real-prereqs) | $(ZSTD) -22 --ultra; $(size_append); } > $@
>
> +quiet_cmd_zstddec = ZSTDDEC $@
> +      cmd_zstddec = cat $(real-prereqs) | $(ZSTD) --decompress > $@
> +


Same here.
Please make this a single process:

   cmd_zstddec = $(ZSTD) --decompress --force --output=$@ $<






One small concern in the future is, if we end up with adding
quiet_cmd_bzip2dec, we will run out of the 7-column of the short log.

 quiet_cmd_bzip2dec = BZIP2DEC$@

We can increase the column size if needed, so I do not think
it is a big issue.










>  # ASM offsets
>  # ---------------------------------------------------------------------------
>
> --
> 2.41.0
>


-- 
Best Regards
Masahiro Yamada