linux-kernel - [PATCH][next] pwm: cros-ec: Avoid -Wflex-array-member-not-at-end warnings

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Message-ID: <aJtRPZpc-Lv-C6zD@kspp>
Date: Tue, 12 Aug 2025 23:35:41 +0900
From: "Gustavo A. R. Silva" <gustavoars@...nel.org>
To: Uwe Kleine-König <ukleinek@...nel.org>,
	Benson Leung <bleung@...omium.org>,
	Guenter Roeck <groeck@...omium.org>
Cc: linux-pwm@...r.kernel.org, chrome-platform@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	linux-hardening@...r.kernel.org
Subject: [PATCH][next] pwm: cros-ec: Avoid -Wflex-array-member-not-at-end
 warnings

-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.

Use the new TRAILING_OVERLAP() helper to fix the following warnings:

drivers/pwm/pwm-cros-ec.c:53:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
drivers/pwm/pwm-cros-ec.c:87:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]

This helper creates a union between a flexible-array member (FAM)
and a set of members that would otherwise follow it. This overlays
the trailing members onto the FAM while preserving the original
memory layout.

Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
---
 drivers/pwm/pwm-cros-ec.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/pwm/pwm-cros-ec.c b/drivers/pwm/pwm-cros-ec.c
index 189301dc395e..67cfa17f58e0 100644
--- a/drivers/pwm/pwm-cros-ec.c
+++ b/drivers/pwm/pwm-cros-ec.c
@@ -49,10 +49,9 @@ static int cros_ec_pwm_set_duty(struct cros_ec_pwm_device *ec_pwm, u8 index,
 				u16 duty)
 {
 	struct cros_ec_device *ec = ec_pwm->ec;
-	struct {
-		struct cros_ec_command msg;
+	TRAILING_OVERLAP(struct cros_ec_command, msg, data,
 		struct ec_params_pwm_set_duty params;
-	} __packed buf;
+	) __packed buf;
 	struct ec_params_pwm_set_duty *params = &buf.params;
 	struct cros_ec_command *msg = &buf.msg;
 	int ret;
@@ -83,13 +82,12 @@ static int cros_ec_pwm_set_duty(struct cros_ec_pwm_device *ec_pwm, u8 index,
 
 static int cros_ec_pwm_get_duty(struct cros_ec_device *ec, bool use_pwm_type, u8 index)
 {
-	struct {
-		struct cros_ec_command msg;
+	TRAILING_OVERLAP(struct cros_ec_command, msg, data,
 		union {
 			struct ec_params_pwm_get_duty params;
 			struct ec_response_pwm_get_duty resp;
 		};
-	} __packed buf;
+	) __packed buf;
 	struct ec_params_pwm_get_duty *params = &buf.params;
 	struct ec_response_pwm_get_duty *resp = &buf.resp;
 	struct cros_ec_command *msg = &buf.msg;
-- 
2.43.0