linux-kernel - [PATCH 2/2] leds: gpio: Add devlinks between the gpio consumed and the gpio leds device

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Date: Tue, 20 Feb 2024 12:11:07 +0100
From: Herve Codina <herve.codina@...tlin.com>
To: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>,
	Pavel Machek <pavel@....cz>,
	Lee Jones <lee@...nel.org>
Cc: linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-leds@...r.kernel.org,
	Luca Ceresoli <luca.ceresoli@...tlin.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	Herve Codina <herve.codina@...tlin.com>
Subject: [PATCH 2/2] leds: gpio: Add devlinks between the gpio consumed and the gpio leds device

When a gpio is removed, the gpio leds consumer need to be removed first.
This dependency consumer/supplier can be described by devlink links.
In case of device-tree, even if some devlinks are created due to the
presence of gpio phandles in the gpio leds children, these links do not
help in removing the gpio leds device (i.e. the real consumer) before
the consumed gpio.
We can reach cases where the gpio are no more present and the gpio leds
driver continue to have leds using these gpio.
Further more, when the gpio come back, the gpio leds still use the old
removed one.

Indeed, the gpio are consumed by the parent of the consumer used in the
devlink creation due to phandles. A link is missing between the gpio and
the real gpio consumer, the gpio leds device itself.

Use the newly introduced gpiod_device_add_link() to create this
missing link between the gpio leds devices and the gpios.
With that done, if a gpio is removed, the gpio leds is removed and the
resources are correctly released.

Signed-off-by: Herve Codina <herve.codina@...tlin.com>
---
 drivers/leds/leds-gpio.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/leds/leds-gpio.c b/drivers/leds/leds-gpio.c
index 83fcd7b6afff..b3ec8ecbe5da 100644
--- a/drivers/leds/leds-gpio.c
+++ b/drivers/leds/leds-gpio.c
@@ -150,6 +150,7 @@ static struct gpio_leds_priv *gpio_leds_create(struct device *dev)
 {
 	struct fwnode_handle *child;
 	struct gpio_leds_priv *priv;
+	struct device_link *link;
 	int count, ret;

 	count = device_get_child_node_count(dev);
@@ -197,6 +198,20 @@ static struct gpio_leds_priv *gpio_leds_create(struct device *dev)
 		/* Set gpiod label to match the corresponding LED name. */
 		gpiod_set_consumer_name(led_dat->gpiod,
 					led_dat->cdev.dev->kobj.name);
+
+		/*
+		 * Create a link between the GPIO and the gpio-leds device.
+		 * This allow to have a relationship between the gpio used and
+		 * the gpio-leds device in order to automatically remove the
+		 * gpio-leds device (consumer) when a GPIO (supplier) is removed.
+		 */
+		link = gpiod_device_add_link(dev, led_dat->gpiod,
+					     DL_FLAG_AUTOREMOVE_CONSUMER);
+		if (IS_ERR(link)) {
+			fwnode_handle_put(child);
+			return ERR_CAST(link);
+		}
+
 		priv->num_leds++;
 	}

-- 
2.43.0