linux-kernel - [PATCH RFC/RFT 08/15] gpio: sysfs: only get the dirent reference for the value attr once

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Message-Id: <20250610-gpio-sysfs-chip-export-v1-8-a8c7aa4478b1@linaro.org>
Date: Tue, 10 Jun 2025 16:38:23 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Ahmad Fatoum <a.fatoum@...gutronix.de>, 
 Kent Gibson <warthog618@...il.com>, 
 Jan Lübbe <jlu@...gutronix.de>, 
 Marek Vasut <marex@...x.de>, Geert Uytterhoeven <geert+renesas@...der.be>, 
 Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH RFC/RFT 08/15] gpio: sysfs: only get the dirent reference
 for the value attr once

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

There's no reason to retrieve the reference to the sysfs dirent every
time we request an interrupt, we can as well only do it once when
exporting the GPIO.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/gpiolib-sysfs.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index a3403b963d6488aad24e47e9e28e0439676de704..642635c9f84bbd869727755e72781fae31a9cca3 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -36,7 +36,7 @@ struct gpiod_data {
 	struct gpio_desc *desc;
 
 	struct mutex mutex;
-	struct kernfs_node *value_kn;
+	struct kernfs_node *value_class_node;
 	int irq;
 	unsigned char irq_flags;
 
@@ -156,7 +156,7 @@ static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
 {
 	struct gpiod_data *data = priv;
 
-	sysfs_notify_dirent(data->value_kn);
+	sysfs_notify_dirent(data->value_class_node);
 
 	return IRQ_HANDLED;
 }
@@ -177,10 +177,6 @@ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 	if (data->irq < 0)
 		return -EIO;
 
-	data->value_kn = sysfs_get_dirent(dev->kobj.sd, "value");
-	if (!data->value_kn)
-		return -ENODEV;
-
 	irq_flags = IRQF_SHARED;
 	if (flags & GPIO_IRQF_TRIGGER_FALLING) {
 		irq_flags |= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
@@ -203,7 +199,7 @@ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 	 */
 	ret = gpiochip_lock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
 	if (ret < 0)
-		goto err_put_kn;
+		goto err_clr_bits;
 
 	ret = request_any_context_irq(data->irq, gpio_sysfs_irq, irq_flags,
 				"gpiolib", data);
@@ -216,10 +212,9 @@ static int gpio_sysfs_request_irq(struct device *dev, unsigned char flags)
 
 err_unlock:
 	gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
-err_put_kn:
+err_clr_bits:
 	clear_bit(FLAG_EDGE_RISING, &desc->flags);
 	clear_bit(FLAG_EDGE_FALLING, &desc->flags);
-	sysfs_put(data->value_kn);
 
 	return ret;
 }
@@ -242,7 +237,6 @@ static void gpio_sysfs_free_irq(struct device *dev)
 	gpiochip_unlock_as_irq(guard.gc, gpio_chip_hwgpio(desc));
 	clear_bit(FLAG_EDGE_RISING, &desc->flags);
 	clear_bit(FLAG_EDGE_FALLING, &desc->flags);
-	sysfs_put(data->value_kn);
 }
 
 static const char *const trigger_names[] = {
@@ -726,8 +720,16 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change)
 		goto err_free_data;
 	}
 
+	data->value_class_node = sysfs_get_dirent(dev->kobj.sd, "value");
+	if (!data->value_class_node) {
+		status = -ENODEV;
+		goto err_unregister_device;
+	}
+
 	return 0;
 
+err_unregister_device:
+	device_unregister(dev);
 err_free_data:
 	kfree(data);
 err_clear_bit:
@@ -804,6 +806,7 @@ void gpiod_unexport(struct gpio_desc *desc)
 
 		data = dev_get_drvdata(dev);
 		clear_bit(FLAG_EXPORT, &desc->flags);
+		sysfs_put(data->value_class_node);
 		device_unregister(dev);
 
 		/*

-- 
2.48.1