gpiolib: of: don't mark hog nodes OF_POPULATED before a chip is found

[PATCH] gpiolib: of: don't mark hog nodes OF_POPULATED before a chip is found

Posted by Abdurrahman Hussain 1 month, 2 weeks ago

When a gpio-hog node is attached by a device-tree overlay before its
parent GPIO chip has been registered, of_gpio_notify() sets
OF_POPULATED on the node via of_node_test_and_set_flag() and only then
discovers that there is no gpio_device for the parent, returning
NOTIFY_DONE without clearing the flag.

Since gpiochip_hog_lines() skips any hog child whose of_node carries
OF_POPULATED, the leaked flag makes the hog silently ignored when the
chip is registered later. Applying an overlay containing both a GPIO
controller node and its hog children - and populating devices only
after the overlay apply completes - hits this on every boot; the hog
is only applied if the chip driver is unbound (which clears the flag
in the remove path) and rebound.

Look up the parent gpio_device before claiming the node so that a hog
attached ahead of its chip stays unclaimed and is picked up normally
by gpiochip_hog_lines() at registration time.

Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Fixes: a23226b7c1f6 ("gpiolib: handle gpio-hogs only once")
Cc: stable@vger.kernel.org
---
 drivers/gpio/gpiolib-of.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 940b566946ce..f36e4b171fa7 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -788,13 +788,13 @@ static int of_gpio_notify(struct notifier_block *nb, unsigned long action,
 		if (!of_property_read_bool(rd->dn, "gpio-hog"))
 			return NOTIFY_DONE;	/* not for us */
 
-		if (of_node_test_and_set_flag(rd->dn, OF_POPULATED))
-			return NOTIFY_DONE;
-
 		gdev = of_find_gpio_device_by_node(rd->dn->parent);
 		if (!gdev)
 			return NOTIFY_DONE;	/* not for us */
 
+		if (of_node_test_and_set_flag(rd->dn, OF_POPULATED))
+			return NOTIFY_DONE;
+
 		ret = gpiochip_add_hog(gpio_device_get_chip(gdev), of_fwnode_handle(rd->dn));
 		if (ret < 0) {
 			pr_err("%s: failed to add hogs for %pOF\n", __func__,

---
base-commit: d58772d8520c7ef247c4b95c9bd76d3a25da9ff5
change-id: 20260815-gpiolib-of-hog-flag-leak-5bac8f98b758

Best regards,
--  
Abdurrahman Hussain <abdurrahman@nexthop.ai>

Re: [PATCH] gpiolib: of: don't mark hog nodes OF_POPULATED before a chip is found

Posted by Bartosz Golaszewski 3 weeks, 6 days ago

On Sat, 15 Aug 2026 13:44:19 -0700, Abdurrahman Hussain wrote:
> When a gpio-hog node is attached by a device-tree overlay before its
> parent GPIO chip has been registered, of_gpio_notify() sets
> OF_POPULATED on the node via of_node_test_and_set_flag() and only then
> discovers that there is no gpio_device for the parent, returning
> NOTIFY_DONE without clearing the flag.
> 
> Since gpiochip_hog_lines() skips any hog child whose of_node carries
> OF_POPULATED, the leaked flag makes the hog silently ignored when the
> chip is registered later. Applying an overlay containing both a GPIO
> controller node and its hog children - and populating devices only
> after the overlay apply completes - hits this on every boot; the hog
> is only applied if the chip driver is unbound (which clears the flag
> in the remove path) and rebound.
> 
> [...]

Applied, thanks!

[1/1] gpiolib: of: don't mark hog nodes OF_POPULATED before a chip is found
      https://git.kernel.org/brgl/c/1f1d0812f6a8ab8e6f709c599f137c99646512cc

Best regards,
-- 
Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>

Re: [PATCH] gpiolib: of: don't mark hog nodes OF_POPULATED before a chip is found

Posted by Daniel Drake 1 month, 1 week ago

On 15/08/2026 21:44, Abdurrahman Hussain wrote:
> When a gpio-hog node is attached by a device-tree overlay before its
> parent GPIO chip has been registered, of_gpio_notify() sets
> OF_POPULATED on the node via of_node_test_and_set_flag() and only then
> discovers that there is no gpio_device for the parent, returning
> NOTIFY_DONE without clearing the flag.
> 
> Since gpiochip_hog_lines() skips any hog child whose of_node carries
> OF_POPULATED, the leaked flag makes the hog silently ignored when the
> chip is registered later. Applying an overlay containing both a GPIO
> controller node and its hog children - and populating devices only
> after the overlay apply completes - hits this on every boot; the hog
> is only applied if the chip driver is unbound (which clears the flag
> in the remove path) and rebound.
> 
> Look up the parent gpio_device before claiming the node so that a hog
> attached ahead of its chip stays unclaimed and is picked up normally
> by gpiochip_hog_lines() at registration time.
> 
> Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
> Fixes: a23226b7c1f6 ("gpiolib: handle gpio-hogs only once")
> Cc: stable@vger.kernel.org
Looks correct, and this is consistent with OF_POPULATED handling in 
of_i2c_notify() and of_spi_notify().

Reviewed-by: Daniel Drake <dan@reactivated.net>