linux-kernel - [PATCH 4/4] pwm: Don't initialize list head before calling list

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Message-Id: <20221115211515.3750209-5-u.kleine-koenig@pengutronix.de>
Date:   Tue, 15 Nov 2022 22:15:15 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Thierry Reding <thierry.reding@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        linux-pwm@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...gutronix.de
Subject: [PATCH 4/4] pwm: Don't initialize list head before calling list_add()

list_add() just overwrites the members of the element to add (here:
chip->list) without any checks, even in the DEBUG_LIST case. So save the
effort to initialize the list.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
---
Hello,

this patch I'm not sure about. A quick grep shows there are (only?) 40
more code locations that call INIT_LIST_HEAD just before list_add().
In my understanding INIT_LIST_HEAD is only to initialize lists, but
chip->list is not a list, but the data needed to track chip as a list
member.

Best regards
Uwe

 drivers/pwm/core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
index b43b24bd3c9f..61bacd8d9b44 100644
--- a/drivers/pwm/core.c
+++ b/drivers/pwm/core.c
@@ -299,7 +299,6 @@ int pwmchip_add(struct pwm_chip *chip)
 		radix_tree_insert(&pwm_tree, pwm->pwm, pwm);
 	}

-	INIT_LIST_HEAD(&chip->list);
 	list_add(&chip->list, &pwm_chips);

 	mutex_unlock(&pwm_lock);
-- 
2.38.1