+ checkpatch-dont-warn-about-enosys-in-userspace-code.patch added to mm-nonmm-unstable branch

+ checkpatch-dont-warn-about-enosys-in-userspace-code.patch added to mm-nonmm-unstable branch

[Andrew Morton]

The patch titled
     Subject: checkpatch: don't warn about ENOSYS in userspace code
has been added to the -mm mm-nonmm-unstable branch.  Its filename is
     checkpatch-dont-warn-about-enosys-in-userspace-code.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/checkpatch-dont-warn-about-enosys-in-userspace-code.patch

This patch will later appear in the mm-nonmm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Kir Kolyshkin <kolyshkin@gmail.com>
Subject: checkpatch: don't warn about ENOSYS in userspace code
Date: Thu, 22 Oct 2026 15:44:21 -0700

The ENOSYS check enforces a kernel ABI rule: the kernel must only return
-ENOSYS for an invalid syscall number. It makes no sense for userspace
code under tools/, where ENOSYS is a regular "Function not implemented"
error, and checking for errno == ENOSYS is the standard way to detect
that a syscall is not available (e.g. to skip a selftest on an older
kernel). There, the warning is always a false positive.

Use the existing is_userspace() helper to skip the check for such files.

Link: https://lore.kernel.org/20261022224426.2756960-3-kolyshkin@gmail.com
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Joe Perches <joe@perches.com>
Cc: Andy Whitcroft <apw@canonical.com>
Cc: Dwaipayan Ray <dwaipayanray1@gmail.com>
Cc: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
---

 scripts/checkpatch.pl |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/scripts/checkpatch.pl~checkpatch-dont-warn-about-enosys-in-userspace-code
+++ a/scripts/checkpatch.pl
@@ -4983,7 +4983,7 @@ sub process {
 # ENOSYS means "bad syscall nr" and nothing else.  This will have a small
 # number of false positives, but assembly files are not checked, so at
 # least the arch entry code will not trigger this warning.
-		if ($line =~ /\bENOSYS\b/) {
+		if ($line =~ /\bENOSYS\b/ && !is_userspace($realfile)) {
 			WARN("ENOSYS",
 			     "ENOSYS means 'invalid syscall nr' and nothing else\n" . $herecurr);
 		}
_

Patches currently in -mm which might be from kolyshkin@gmail.com are

checkpatch-is_userspace-exclude-kernel-code-under-tools.patch
checkpatch-dont-warn-about-enosys-in-userspace-code.patch
checkpatch-dont-warn-about-bug-in-userspace-code.patch
checkpatch-dont-suggest-kstrtotype-in-userspace-code.patch