[PATCH 2/4] checkpatch: don't warn about ENOSYS in userspace code

[Kir Kolyshkin]

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.

Signed-off-by: Kir Kolyshkin <kolyshkin@xxxxxxxxx>
---
 scripts/checkpatch.pl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 8f9a46d809ae..a97d5748878b 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -4985,7 +4985,7 @@ 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);
 		}
-- 
2.56.0