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 Restructured Text 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.
Masahiro Yamada
authored
When building with 'make -s', no output to stdout should be printed.
As Arnd Bergmann reported [1], mkimage shows the detailed information
of the generated images.
I think this should be suppressed by the 'cmd' macro instead of by
individual scripts.
Insert 'exec >/dev/null;' in order to redirect stdout to /dev/null for
silent builds.
[Note about this implementation]
'exec >/dev/null;' may look somewhat tricky, but this has a reason.
Appending '>/dev/null' at the end of command line is a common way for
redirection, so I first tried this:
cmd = @set -e; $(echo-cmd) $(cmd_$(1)) >/dev/null
... but it would not work if $(cmd_$(1)) itself contains a redirection.
For example, cmd_wrap in scripts/Makefile.asm-generic redirects the
output from the 'echo' command into the target file.
It would be expanded into:
echo "#include <asm-generic/$*.h>" > $@ >/dev/null
Then, the target file gets empty because the string will go to /dev/null
instead of $@.
Next, I tried this:
cmd = @set -e; $(echo-cmd) { $(cmd_$(1)); } >/dev/null
The form above would be expanded into:
{ echo "#include <asm-generic/$*.h>" > $@; } >/dev/null
This works as expected. However, it would be a syntax error if
$(cmd_$(1)) is empty.
When CONFIG_TRIM_UNUSED_KSYMS is disabled, $(call cmd,gen_ksymdeps) in
scripts/Makefile.build would be expanded into:
set -e; { ; } >/dev/null
..., which causes an syntax error.
I also tried this:
cmd = @set -e; $(echo-cmd) ( $(cmd_$(1)) ) >/dev/null
... but this causes a syntax error for the same reason.
So, finally I adopted:
cmd = @set -e; $(echo-cmd) exec >/dev/null; $(cmd_$(1))
[1]: https://lore.kernel.org/lkml/20210514135752.2910387-1-arnd@kernel.org/
Signed-off-by: 
Masahiro Yamada <masahiroy@kernel.org>| Name | Last commit | Last update |
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| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README |