linux-kernel - [PATCH] gpiolib: fix efficiency regression when using gpio_chip_get

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Message-Id: <20250703191829.2952986-1-hugo@hugovil.com>
Date: Thu,  3 Jul 2025 15:18:29 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>
Cc: hugo@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	stable@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] gpiolib: fix efficiency regression when using gpio_chip_get_multiple()

From: Hugo Villeneuve <hvilleneuve@...onoff.com>

commit 74abd086d2ee ("gpiolib: sanitize the return value of
gpio_chip::get_multiple()") altered the value returned by
gc->get_multiple() in case it is positive (> 0), but failed to
return for other cases (<= 0).

This may result in the "if (gc->get)" block being executed and thus
negates the performance gain that is normally obtained by using
gc->get_multiple().

Fix by returning the result of gc->get_multiple() if it is <= 0.

Also move the "ret" variable to the scope where it is used, which as an
added bonus fixes an indentation error introduced by the aforementioned
commit.

Fixes: 74abd086d2ee ("gpiolib: sanitize the return value of gpio_chip::get_multiple()")
Cc: stable@...r.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
 drivers/gpio/gpiolib.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index fdafa0df1b43..3a3eca5b4c40 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -3297,14 +3297,15 @@ static int gpiod_get_raw_value_commit(const struct gpio_desc *desc)
 static int gpio_chip_get_multiple(struct gpio_chip *gc,
 				  unsigned long *mask, unsigned long *bits)
 {
-	int ret;
-	
 	lockdep_assert_held(&gc->gpiodev->srcu);
 
 	if (gc->get_multiple) {
+		int ret;
+
 		ret = gc->get_multiple(gc, mask, bits);
 		if (ret > 0)
 			return -EBADE;
+		return ret;
 	}
 
 	if (gc->get) {

base-commit: b4911fb0b060899e4eebca0151eb56deb86921ec
-- 
2.39.5