FAILED: patch "[PATCH] kbuild: sink stdout from cmd for silent build" failed to apply to 5.4-stable tree

The patch below does not apply to the 5.4-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 174a1dcc96429efce4ef7eb2f5c4506480da2182 Mon Sep 17 00:00:00 2001
From: Masahiro Yamada <[email protected]>
Date: Mon, 17 May 2021 16:03:13 +0900
Subject: [PATCH] kbuild: sink stdout from cmd for silent build

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/[email protected]/

index 82dd1b65b7a8..f247e691562d 100644
@@ -90,8 +90,13 @@ clean := -f $(srctree)/scripts/Makefile.clean obj
 echo-cmd = $(if $($(quiet)cmd_$(1)),\
 	echo '  $(call escsq,$($(quiet)cmd_$(1)))$(echo-why)';)
 
+# sink stdout for 'make -s'
+       redirect :=
+ quiet_redirect :=
+silent_redirect := exec >/dev/null;
+
 # printing commands
-cmd = @set -e; $(echo-cmd) $(cmd_$(1))
+cmd = @set -e; $(echo-cmd) $($(quiet)redirect) $(cmd_$(1))
 
 ###
 # if_changed      - execute command if any prerequisite is newer than