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The 'cpio' command is used solely for copying header files to the
temporary directory. However, there is no strong reason to use 'cpio'
for this purpose. For example, scripts/package/install-extmod-build
uses the 'tar' command to copy files.
This commit replaces the use of 'cpio' with 'tar' because 'tar' is
already used in this script to generate kheaders_data.tar.xz anyway.
Performance-wide, there is no significant difference between 'cpio'
and 'tar'.
[Before]
$ rm -fr kheaders; mkdir kheaders
$ time sh -c '
for f in include arch/x86/include
do
find "$f" -name "*.h"
done | cpio --quiet -pd kheaders
'
real 0m0.148s
user 0m0.021s
sys 0m0.140s
[After]
$ rm -fr kheaders; mkdir kheaders
$ time sh -c '
for f in include arch/x86/include
do
find "$f" -name "*.h"
done | tar -c -f - -T - | tar -xf - -C kheaders
'
real 0m0.098s
user 0m0.024s
sys 0m0.131s
Revert commit 69ef0920bd ("Docs: Add cpio requirement to changes.rst")
because 'cpio' is not used anywhere else during the kernel build.
Please note that the built-in initramfs is created by the in-tree tool,
usr/gen_init_cpio, so it does not rely on the external 'cpio' command
at all.
Remove 'cpio' from the package build dependencies as well.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.