[PATCH] checkpatch: Do not complain about positive return values starting with EPOLL

[PATCH] checkpatch: Do not complain about positive return values starting with EPOLL

[Guenter Roeck]

checkpatch complains about positive return values of poll functions.
Example:

WARNING: return of an errno should typically be negative (ie: return -EPOLLIN)
+		return EPOLLIN;

Poll functions return positive values. The defines for the return values
of poll functions all start with EPOLL, resulting in a number of false
positives. An often used workaround is to assign poll function return
values to variables and returning that variable, but that is a less than
perfect solution.

There is no error definition which starts with EPOLL, so it is safe to omit
the warning for return values starting with EPOLL.

Cc: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 scripts/checkpatch.pl | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index 23697a6b1eaa..cf82dbd7d9d1 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -5458,7 +5458,8 @@ sub process {
 # Return of what appears to be an errno should normally be negative
 		if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
 			my $name = $1;
-			if ($name ne 'EOF' && $name ne 'ERROR') {
+			if ($name ne 'EOF' && $name ne 'ERROR' &&
+			    rindex($name, 'EPOLL', 0) != 0) {
 				WARN("USE_NEGATIVE_ERRNO",
 				     "return of an errno should typically be negative (ie: return -$1)\n" . $herecurr);
 			}
-- 
2.25.1

Re: [PATCH] checkpatch: Do not complain about positive return values starting with EPOLL

[Joe Perches]

On Sun, 2021-06-20 at 08:45 -0700, Guenter Roeck wrote:
> checkpatch complains about positive return values of poll functions.
> Example:
> 
> WARNING: return of an errno should typically be negative (ie: return -EPOLLIN)
> +		return EPOLLIN;
> 
> Poll functions return positive values. The defines for the return values
> of poll functions all start with EPOLL, resulting in a number of false
> positives. An often used workaround is to assign poll function return
> values to variables and returning that variable, but that is a less than
> perfect solution.
> 
> There is no error definition which starts with EPOLL, so it is safe to omit
> the warning for return values starting with EPOLL.

Seems OK but

> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
[]
> @@ -5458,7 +5458,8 @@ sub process {
>  # Return of what appears to be an errno should normally be negative
>  		if ($sline =~ /\breturn(?:\s*\(+\s*|\s+)(E[A-Z]+)(?:\s*\)+\s*|\s*)[;:,]/) {
>  			my $name = $1;
> -			if ($name ne 'EOF' && $name ne 'ERROR') {
> +			if ($name ne 'EOF' && $name ne 'ERROR' &&
> +			    rindex($name, 'EPOLL', 0) != 0) {

rindex is a bit harder to read so my preference would be for the simpler:

			if ($name ne 'EOF' && $name ne 'ERROR' && $name !~ /^EPOLL/) {

>  				WARN("USE_NEGATIVE_ERRNO",
>  				     "return of an errno should typically be negative (ie: return -$1)\n" . $herecurr);
>  			}