linux-kernel - [PATCH 2/6] hid: cp2112: hold the lock for the entire direction

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Message-Id: <20250423-gpiochip-set-rv-hid-v1-2-2e6762b582f6@linaro.org>
Date: Wed, 23 Apr 2025 10:55:40 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Jiri Kosina <jikos@...nel.org>, Benjamin Tissoires <bentiss@...nel.org>, 
 Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>, Rishi Gupta <gupt21@...il.com>
Cc: linux-input@...r.kernel.org, linux-kernel@...r.kernel.org, 
 linux-gpio@...r.kernel.org, linux-i2c@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 2/6] hid: cp2112: hold the lock for the entire
 direction_output() call

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

We currently take the lock, set direction to output, release it,
reacquire it and set the desired value. That doesn't look correct.
Introduce a helper function that sets the value without taking the lock
and use it where applicable in order to combine the critical sections.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/hid/hid-cp2112.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/drivers/hid/hid-cp2112.c b/drivers/hid/hid-cp2112.c
index a001b9acd2d4..408c865efdd4 100644
--- a/drivers/hid/hid-cp2112.c
+++ b/drivers/hid/hid-cp2112.c
@@ -17,6 +17,7 @@
  */
 
 #include <linux/bitops.h>
+#include <linux/cleanup.h>
 #include <linux/gpio/driver.h>
 #include <linux/hid.h>
 #include <linux/hidraw.h>
@@ -218,15 +219,13 @@ static int cp2112_gpio_direction_input(struct gpio_chip *chip, unsigned offset)
 	return ret;
 }
 
-static void cp2112_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
+static void cp2112_gpio_set_unlocked(struct cp2112_device *dev,
+				     unsigned int offset, int value)
 {
-	struct cp2112_device *dev = gpiochip_get_data(chip);
 	struct hid_device *hdev = dev->hdev;
 	u8 *buf = dev->in_out_buffer;
 	int ret;
 
-	mutex_lock(&dev->lock);
-
 	buf[0] = CP2112_GPIO_SET;
 	buf[1] = value ? CP2112_GPIO_ALL_GPIO_MASK : 0;
 	buf[2] = BIT(offset);
@@ -236,8 +235,16 @@ static void cp2112_gpio_set(struct gpio_chip *chip, unsigned offset, int value)
 				 HID_REQ_SET_REPORT);
 	if (ret < 0)
 		hid_err(hdev, "error setting GPIO values: %d\n", ret);
+}
 
-	mutex_unlock(&dev->lock);
+static void cp2112_gpio_set(struct gpio_chip *chip, unsigned int offset,
+			    int value)
+{
+	struct cp2112_device *dev = gpiochip_get_data(chip);
+
+	guard(mutex)(&dev->lock);
+
+	return cp2112_gpio_set_unlocked(dev, offset, value);
 }
 
 static int cp2112_gpio_get_all(struct gpio_chip *chip)
@@ -306,13 +313,13 @@ static int cp2112_gpio_direction_output(struct gpio_chip *chip,
 		goto fail;
 	}
 
-	mutex_unlock(&dev->lock);
-
 	/*
 	 * Set gpio value when output direction is already set,
 	 * as specified in AN495, Rev. 0.2, cpt. 4.4
 	 */
-	cp2112_gpio_set(chip, offset, value);
+	cp2112_gpio_set_unlocked(dev, offset, value);
+
+	mutex_unlock(&dev->lock);
 
 	return 0;
 

-- 
2.45.2