linux-kernel - [PATCH v3 08/24] gpio: sysfs: use gpio_device

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Date: Thu,  8 Feb 2024 10:59:04 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>,
	Kent Gibson <warthog618@...il.com>,
	Alex Elder <elder@...aro.org>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
	Wolfram Sang <wsa@...-dreams.de>
Cc: linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH v3 08/24] gpio: sysfs: use gpio_device_find() to iterate over existing devices

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

With the list of GPIO devices now protected with SRCU we can use
gpio_device_find() to traverse it from sysfs.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>
---
 drivers/gpio/gpiolib-sysfs.c | 46 ++++++++++++++++++------------------
 drivers/gpio/gpiolib.c       |  2 +-
 drivers/gpio/gpiolib.h       |  1 -
 3 files changed, 24 insertions(+), 25 deletions(-)

diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index 6bf5332136e5..d6ff044ce887 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -790,11 +790,29 @@ void gpiochip_sysfs_unregister(struct gpio_device *gdev)
 	}
 }
 
+/*
+ * We're not really looking for a device - we just want to iterate over the
+ * list and call this callback for each GPIO device. This is why this function
+ * always returns 0.
+ */
+static int gpiofind_sysfs_register(struct gpio_chip *gc, void *data)
+{
+	struct gpio_device *gdev = gc->gpiodev;
+	int ret;
+
+	if (gdev->mockdev)
+		return 0;
+
+	ret = gpiochip_sysfs_register(gdev);
+	if (ret)
+		chip_err(gc, "failed to register the sysfs entry: %d\n", ret);
+
+	return 0;
+}
+
 static int __init gpiolib_sysfs_init(void)
 {
-	int		status;
-	unsigned long	flags;
-	struct gpio_device *gdev;
+	int status;
 
 	status = class_register(&gpio_class);
 	if (status < 0)
@@ -806,26 +824,8 @@ static int __init gpiolib_sysfs_init(void)
 	 * We run before arch_initcall() so chip->dev nodes can have
 	 * registered, and so arch_initcall() can always gpiod_export().
 	 */
-	spin_lock_irqsave(&gpio_lock, flags);
-	list_for_each_entry(gdev, &gpio_devices, list) {
-		if (gdev->mockdev)
-			continue;
+	(void)gpio_device_find(NULL, gpiofind_sysfs_register);
 
-		/*
-		 * TODO we yield gpio_lock here because
-		 * gpiochip_sysfs_register() acquires a mutex. This is unsafe
-		 * and needs to be fixed.
-		 *
-		 * Also it would be nice to use gpio_device_find() here so we
-		 * can keep gpio_chips local to gpiolib.c, but the yield of
-		 * gpio_lock prevents us from doing this.
-		 */
-		spin_unlock_irqrestore(&gpio_lock, flags);
-		status = gpiochip_sysfs_register(gdev);
-		spin_lock_irqsave(&gpio_lock, flags);
-	}
-	spin_unlock_irqrestore(&gpio_lock, flags);
-
-	return status;
+	return 0;
 }
 postcore_initcall(gpiolib_sysfs_init);
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a87ab8f013c4..68543ab34fb6 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -85,7 +85,7 @@ DEFINE_SPINLOCK(gpio_lock);
 static DEFINE_MUTEX(gpio_lookup_lock);
 static LIST_HEAD(gpio_lookup_list);
 
-LIST_HEAD(gpio_devices);
+static LIST_HEAD(gpio_devices);
 /* Protects the GPIO device list against concurrent modifications. */
 static DEFINE_MUTEX(gpio_devices_lock);
 /* Ensures coherence during read-only accesses to the list of GPIO devices. */
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index d2e73eea9e92..2bf3f9e13ae4 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -136,7 +136,6 @@ int gpiod_set_array_value_complex(bool raw, bool can_sleep,
 int gpiod_set_transitory(struct gpio_desc *desc, bool transitory);
 
 extern spinlock_t gpio_lock;
-extern struct list_head gpio_devices;
 
 void gpiod_line_state_notify(struct gpio_desc *desc, unsigned long action);
 
-- 
2.40.1