From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Date: Fri, 5 Jan 2024 12:12:45 +0000 (+0100)
Subject: gpio: of: assign and read the hog pointer atomically
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=8ce6fd81a452d554889874e50cd34e92cf4547d6;p=linux.git

gpio: of: assign and read the hog pointer atomically

The device nodes representing GPIO hogs cannot be deleted without
unregistering the GPIO chip so there's no need to serialize their access.
However we must ensure that users can get the right address so write and
read it atomically.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 35d717fd393f2..523b047a28035 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -801,7 +801,7 @@ static int of_gpiochip_add_hog(struct gpio_chip *chip, struct device_node *hog)
 			return ret;
 
 #ifdef CONFIG_OF_DYNAMIC
-		desc->hog = hog;
+		WRITE_ONCE(desc->hog, hog);
 #endif
 	}
 
@@ -849,7 +849,7 @@ static void of_gpiochip_remove_hog(struct gpio_chip *chip,
 	struct gpio_desc *desc;
 
 	for_each_gpio_desc_with_flag(chip, desc, FLAG_IS_HOGGED)
-		if (desc->hog == hog)
+		if (READ_ONCE(desc->hog) == hog)
 			gpiochip_free_own_desc(desc);
 }
 
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a5598c3299ffe..03d7c3f92f5e3 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2330,7 +2330,7 @@ static bool gpiod_free_commit(struct gpio_desc *desc)
 		clear_bit(FLAG_EDGE_FALLING, &desc->flags);
 		clear_bit(FLAG_IS_HOGGED, &desc->flags);
 #ifdef CONFIG_OF_DYNAMIC
-		desc->hog = NULL;
+		WRITE_ONCE(desc->hog, NULL);
 #endif
 		ret = true;
 	}