[PATCH v5 00/13] notifier: add device-managed registration APIs and convert drivers

[PATCH v5 00/13] notifier: add device-managed registration APIs and convert drivers

[Eliav Farber]

Many drivers repeat the same boilerplate when registering notifiers with
device lifetime:

  1. Register the notifier with *_notifier_chain_register()
  2. Check for error
  3. Register a devm action to unregister on teardown
  4. Implement a per-driver static unregister callback

This series adds devm_atomic_notifier_chain_register() and
devm_blocking_notifier_chain_register() that automatically unregister
the notifier when the device is unbound, then converts 11 drivers to use
them.

Each conversion eliminates a per-driver unregister callback and the
associated devm_add_action_or_reset() call, reducing code by ~15 lines
per driver.

The implementation follows the established devres pattern used by other
device-managed kernel APIs.

Changes in v5:
- Patch 1: rename notifier_block parameter from 'n' to 'nb' to match
  the devres struct field name (Uwe Kleine-König)
- Patch 2: remove extra blank line left after deleting the unregister
  callback (Uwe Kleine-König)

Changes in v4:
- Patch 8: split the removal of unused
  ghes_register_vendor_record_notifier() and
  ghes_unregister_vendor_record_notifier() into a separate preceding
  patch (Andy Shevchenko)

Changes in v3:
- Patch 1: drop devm_raw_notifier_chain_register() since raw notifiers
  require caller-provided locking which is incompatible with the devres
  teardown callback (Sashiko)
- Patch 12: fix commit message to accurately describe the old code as
  using devres_alloc() + register_reboot_notifier() (Sashiko)

Changes in v2:
- Patch 1: drop 'extern' from new function prototypes (Bart Van Assche)
- Patch 1: fix kerneldoc to use 'Return:' format (Bart Van Assche)
- Patch 1: use <linux/device/devres.h> instead of <linux/device.h>
  (Andy Shevchenko)
- Patch 8: also remove unused ghes_register_vendor_record_notifier() and
  ghes_unregister_vendor_record_notifier() along with their exports and
  ghes.h declarations (Jonathan Cameron)

Eliav Farber (13):
  notifier: add device-managed registration APIs
  pwm: iqs620a: use devm_blocking_notifier_chain_register()
  iio: light: iqs621-als: use devm_blocking_notifier_chain_register()
  iio: position: iqs624: use devm_blocking_notifier_chain_register()
  gpio: adp5585: use devm_blocking_notifier_chain_register()
  platform/x86: bitland-mifs-wmi: use
    devm_blocking_notifier_chain_register()
  Input: adp5585: use devm_blocking_notifier_chain_register()
  ACPI: APEI: GHES: remove unused
    ghes_{,un}register_vendor_record_notifier()
  ACPI: APEI: GHES: use devm_blocking_notifier_chain_register()
  platform/x86: uniwill-wmi: use devm_blocking_notifier_chain_register()
  gpio: eic-sprd: use devm_atomic_notifier_chain_register()
  gpio: gpiolib-kunit: use devm_blocking_notifier_chain_register()
  reboot: use devm_blocking_notifier_chain_register()

 drivers/acpi/apei/ghes.c                   |  27 +-----
 drivers/gpio/gpio-adp5585.c                |  20 +---
 drivers/gpio/gpio-eic-sprd.c               |  17 +---
 drivers/gpio/gpiolib-kunit.c               |  14 +--
 drivers/iio/light/iqs621-als.c             |  24 +----
 drivers/iio/position/iqs624-pos.c          |  24 +----
 drivers/input/keyboard/adp5585-keys.c      |  18 +---
 drivers/platform/x86/bitland-mifs-wmi.c    |  17 +---
 drivers/platform/x86/uniwill/uniwill-wmi.c |  17 +---
 drivers/pwm/pwm-iqs620a.c                  |  23 +----
 include/acpi/ghes.h                        |  16 ----
 include/linux/notifier.h                   |   7 ++
 kernel/notifier.c                          | 103 +++++++++++++++++++++
 kernel/reboot.c                            |  24 +----
 14 files changed, 140 insertions(+), 211 deletions(-)

-- 
2.47.3

[PATCH v5 01/13] notifier: add device-managed registration APIs

[Eliav Farber]

Add devm_atomic_notifier_chain_register() and
devm_blocking_notifier_chain_register() that automatically unregister
the notifier when the device is unbound.

Many drivers repeat the same boilerplate pattern:

  1. Register the notifier with *_notifier_chain_register()
  2. Check for error
  3. Register a devm action to unregister on teardown
  4. Implement a per-driver static unregister callback

With the new devm_*_notifier_chain_register() APIs, this reduces to a
single call with one error path, eliminating per-driver unregister
callbacks entirely.

The implementation follows the established devres pattern used by other
device-managed kernel APIs.

A devm variant for raw notifier chains is intentionally not included
because raw notifiers require the caller to provide all locking. The
devres teardown callback has no way to acquire the caller's lock, and
devres_alloc() with GFP_KERNEL cannot be used if the caller's lock is a
spinlock.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
Changes in v5:
- Rename notifier_block parameter from 'n' to 'nb' to match the devres
  struct field name (Uwe Kleine-König)

Changes in v3:
- Drop devm_raw_notifier_chain_register() since raw notifiers require
  caller-provided locking which is incompatible with the devres teardown
  callback (Sashiko)

Changes in v2:
- Drop 'extern' from new function prototypes (Bart Van Assche)
- Fix kerneldoc to use 'Return:' format (Bart Van Assche)
- Use <linux/device/devres.h> instead of <linux/device.h> (Andy Shevchenko)

 include/linux/notifier.h |   7 +++
 kernel/notifier.c        | 103 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)

diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 01b6c9d9956f..4eeae9741a6e 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -46,6 +46,7 @@
  * often but notifier_blocks will seldom be removed.
  */
 
+struct device;
 struct notifier_block;
 
 typedef	int (*notifier_fn_t)(struct notifier_block *nb,
@@ -145,8 +146,14 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
 
 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
 		struct notifier_block *nb);
+int devm_atomic_notifier_chain_register(struct device *dev,
+		struct atomic_notifier_head *nh,
+		struct notifier_block *nb);
 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
 		struct notifier_block *nb);
+int devm_blocking_notifier_chain_register(struct device *dev,
+		struct blocking_notifier_head *nh,
+		struct notifier_block *nb);
 extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
 		struct notifier_block *nb);
 extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
diff --git a/kernel/notifier.c b/kernel/notifier.c
index 2f9fe7c30287..0c39627ea69c 100644
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-only
+#include <linux/device/devres.h>
 #include <linux/kdebug.h>
 #include <linux/kprobes.h>
 #include <linux/export.h>
@@ -197,6 +198,56 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
 }
 EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
 
+struct atomic_notifier_chain_devres {
+	struct atomic_notifier_head *nh;
+	struct notifier_block *nb;
+};
+
+static void devm_atomic_notifier_chain_unregister(struct device *dev, void *res)
+{
+	struct atomic_notifier_chain_devres *dr = res;
+
+	atomic_notifier_chain_unregister(dr->nh, dr->nb);
+}
+
+/**
+ *	devm_atomic_notifier_chain_register - Device-managed atomic notifier registration
+ *	@dev: Device to tie the notifier lifetime to
+ *	@nh: Pointer to head of the atomic notifier chain
+ *	@nb: New entry in notifier chain
+ *
+ *	Adds a notifier to an atomic notifier chain and registers a cleanup
+ *	action to automatically unregister it when @dev is unbound.
+ *
+ *	Return:
+ *	0 on success, negative errno on error.
+ */
+int devm_atomic_notifier_chain_register(struct device *dev,
+					struct atomic_notifier_head *nh,
+					struct notifier_block *nb)
+{
+	struct atomic_notifier_chain_devres *dr;
+	int ret;
+
+	dr = devres_alloc(devm_atomic_notifier_chain_unregister,
+			  sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	ret = atomic_notifier_chain_register(nh, nb);
+	if (ret) {
+		devres_free(dr);
+		return ret;
+	}
+
+	dr->nh = nh;
+	dr->nb = nb;
+	devres_add(dev, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_atomic_notifier_chain_register);
+
 /**
  *	atomic_notifier_call_chain - Call functions in an atomic notifier chain
  *	@nh: Pointer to head of the atomic notifier chain
@@ -349,6 +400,58 @@ int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
 }
 EXPORT_SYMBOL_GPL(blocking_notifier_call_chain_robust);
 
+struct blocking_notifier_chain_devres {
+	struct blocking_notifier_head *nh;
+	struct notifier_block *nb;
+};
+
+static void devm_blocking_notifier_chain_unregister(struct device *dev,
+						    void *res)
+{
+	struct blocking_notifier_chain_devres *dr = res;
+
+	blocking_notifier_chain_unregister(dr->nh, dr->nb);
+}
+
+/**
+ *	devm_blocking_notifier_chain_register - Device-managed blocking notifier registration
+ *	@dev: Device to tie the notifier lifetime to
+ *	@nh: Pointer to head of the blocking notifier chain
+ *	@nb: New entry in notifier chain
+ *
+ *	Adds a notifier to a blocking notifier chain and registers a cleanup
+ *	action to automatically unregister it when @dev is unbound.
+ *	Must be called in process context.
+ *
+ *	Return:
+ *	0 on success, negative errno on error.
+ */
+int devm_blocking_notifier_chain_register(struct device *dev,
+					  struct blocking_notifier_head *nh,
+					  struct notifier_block *nb)
+{
+	struct blocking_notifier_chain_devres *dr;
+	int ret;
+
+	dr = devres_alloc(devm_blocking_notifier_chain_unregister,
+			  sizeof(*dr), GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	ret = blocking_notifier_chain_register(nh, nb);
+	if (ret) {
+		devres_free(dr);
+		return ret;
+	}
+
+	dr->nh = nh;
+	dr->nb = nb;
+	devres_add(dev, dr);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(devm_blocking_notifier_chain_register);
+
 /**
  *	blocking_notifier_call_chain - Call functions in a blocking notifier chain
  *	@nh: Pointer to head of the blocking notifier chain
-- 
2.47.3

[PATCH v5 02/13] pwm: iqs620a: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
iqs620_pwm_notifier_unregister() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
Changes in v5:
- Remove extra blank line left after deleting the unregister callback
  (Uwe Kleine-König)

 drivers/pwm/pwm-iqs620a.c | 23 +++--------------------
 1 file changed, 3 insertions(+), 20 deletions(-)

diff --git a/drivers/pwm/pwm-iqs620a.c b/drivers/pwm/pwm-iqs620a.c
index 13e5e138c8e9..6c6caee65b8f 100644
--- a/drivers/pwm/pwm-iqs620a.c
+++ b/drivers/pwm/pwm-iqs620a.c
@@ -173,18 +173,6 @@ static const struct pwm_ops iqs620_pwm_ops = {
 	.get_state = iqs620_pwm_get_state,
 };
 
-static void iqs620_pwm_notifier_unregister(void *context)
-{
-	struct iqs620_pwm_private *iqs620_pwm = context;
-	int ret;
-
-	ret = blocking_notifier_chain_unregister(&iqs620_pwm->iqs62x->nh,
-						 &iqs620_pwm->notifier);
-	if (ret)
-		dev_err(iqs620_pwm->dev,
-			"Failed to unregister notifier: %d\n", ret);
-}
-
 static int iqs620_pwm_probe(struct platform_device *pdev)
 {
 	struct iqs62x_core *iqs62x = dev_get_drvdata(pdev->dev.parent);
@@ -218,19 +206,14 @@ static int iqs620_pwm_probe(struct platform_device *pdev)
 	mutex_init(&iqs620_pwm->lock);
 
 	iqs620_pwm->notifier.notifier_call = iqs620_pwm_notifier;
-	ret = blocking_notifier_chain_register(&iqs620_pwm->iqs62x->nh,
-					       &iqs620_pwm->notifier);
+	ret = devm_blocking_notifier_chain_register(&pdev->dev,
+						    &iqs620_pwm->iqs62x->nh,
+						    &iqs620_pwm->notifier);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
 		return ret;
 	}
 
-	ret = devm_add_action_or_reset(&pdev->dev,
-				       iqs620_pwm_notifier_unregister,
-				       iqs620_pwm);
-	if (ret)
-		return ret;
-
 	ret = devm_pwmchip_add(&pdev->dev, chip);
 	if (ret)
 		dev_err(&pdev->dev, "Failed to add device: %d\n", ret);
-- 
2.47.3

[PATCH v5 03/13] iio: light: iqs621-als: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
iqs621_als_notifier_unregister() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
 drivers/iio/light/iqs621-als.c | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/drivers/iio/light/iqs621-als.c b/drivers/iio/light/iqs621-als.c
index cd5843e3e2c3..f9d215ef1970 100644
--- a/drivers/iio/light/iqs621-als.c
+++ b/drivers/iio/light/iqs621-als.c
@@ -179,19 +179,6 @@ static int iqs621_als_notifier(struct notifier_block *notifier,
 	return NOTIFY_OK;
 }
 
-static void iqs621_als_notifier_unregister(void *context)
-{
-	struct iqs621_als_private *iqs621_als = context;
-	struct iio_dev *indio_dev = iqs621_als->indio_dev;
-	int ret;
-
-	ret = blocking_notifier_chain_unregister(&iqs621_als->iqs62x->nh,
-						 &iqs621_als->notifier);
-	if (ret)
-		dev_err(indio_dev->dev.parent,
-			"Failed to unregister notifier: %d\n", ret);
-}
-
 static int iqs621_als_read_raw(struct iio_dev *indio_dev,
 			       struct iio_chan_spec const *chan,
 			       int *val, int *val2, long mask)
@@ -563,19 +550,14 @@ static int iqs621_als_probe(struct platform_device *pdev)
 	mutex_init(&iqs621_als->lock);
 
 	iqs621_als->notifier.notifier_call = iqs621_als_notifier;
-	ret = blocking_notifier_chain_register(&iqs621_als->iqs62x->nh,
-					       &iqs621_als->notifier);
+	ret = devm_blocking_notifier_chain_register(&pdev->dev,
+						    &iqs621_als->iqs62x->nh,
+						    &iqs621_als->notifier);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
 		return ret;
 	}
 
-	ret = devm_add_action_or_reset(&pdev->dev,
-				       iqs621_als_notifier_unregister,
-				       iqs621_als);
-	if (ret)
-		return ret;
-
 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }
 
-- 
2.47.3

[PATCH v5 04/13] iio: position: iqs624: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
iqs624_pos_notifier_unregister() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
 drivers/iio/position/iqs624-pos.c | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/drivers/iio/position/iqs624-pos.c b/drivers/iio/position/iqs624-pos.c
index 8239239c6ee2..d2aa2df71457 100644
--- a/drivers/iio/position/iqs624-pos.c
+++ b/drivers/iio/position/iqs624-pos.c
@@ -96,19 +96,6 @@ static int iqs624_pos_notifier(struct notifier_block *notifier,
 	return ret;
 }
 
-static void iqs624_pos_notifier_unregister(void *context)
-{
-	struct iqs624_pos_private *iqs624_pos = context;
-	struct iio_dev *indio_dev = iqs624_pos->indio_dev;
-	int ret;
-
-	ret = blocking_notifier_chain_unregister(&iqs624_pos->iqs62x->nh,
-						 &iqs624_pos->notifier);
-	if (ret)
-		dev_err(indio_dev->dev.parent,
-			"Failed to unregister notifier: %d\n", ret);
-}
-
 static int iqs624_pos_angle_get(struct iqs62x_core *iqs62x, unsigned int *val)
 {
 	int ret;
@@ -255,19 +242,14 @@ static int iqs624_pos_probe(struct platform_device *pdev)
 	mutex_init(&iqs624_pos->lock);
 
 	iqs624_pos->notifier.notifier_call = iqs624_pos_notifier;
-	ret = blocking_notifier_chain_register(&iqs624_pos->iqs62x->nh,
-					       &iqs624_pos->notifier);
+	ret = devm_blocking_notifier_chain_register(&pdev->dev,
+						    &iqs624_pos->iqs62x->nh,
+						    &iqs624_pos->notifier);
 	if (ret) {
 		dev_err(&pdev->dev, "Failed to register notifier: %d\n", ret);
 		return ret;
 	}
 
-	ret = devm_add_action_or_reset(&pdev->dev,
-				       iqs624_pos_notifier_unregister,
-				       iqs624_pos);
-	if (ret)
-		return ret;
-
 	return devm_iio_device_register(&pdev->dev, indio_dev);
 }
 
-- 
2.47.3

[PATCH v5 05/13] gpio: adp5585: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
adp5585_gpio_unreg_notifier() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 drivers/gpio/gpio-adp5585.c | 20 +++-----------------
 1 file changed, 3 insertions(+), 17 deletions(-)

diff --git a/drivers/gpio/gpio-adp5585.c b/drivers/gpio/gpio-adp5585.c
index 6f10fc646008..7c04a7e86c8f 100644
--- a/drivers/gpio/gpio-adp5585.c
+++ b/drivers/gpio/gpio-adp5585.c
@@ -390,16 +390,6 @@ static const struct irq_chip adp5585_irq_chip = {
 	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
-static void adp5585_gpio_unreg_notifier(void *data)
-{
-	struct adp5585_gpio_dev *adp5585_gpio = data;
-	struct device *dev = adp5585_gpio->gpio_chip.parent;
-	struct adp5585_dev *adp5585 = dev_get_drvdata(dev->parent);
-
-	blocking_notifier_chain_unregister(&adp5585->event_notifier,
-					   &adp5585_gpio->nb);
-}
-
 static int adp5585_gpio_probe(struct platform_device *pdev)
 {
 	struct adp5585_dev *adp5585 = dev_get_drvdata(pdev->dev.parent);
@@ -450,13 +440,9 @@ static int adp5585_gpio_probe(struct platform_device *pdev)
 		girq->threaded = true;
 
 		adp5585_gpio->nb.notifier_call = adp5585_gpio_key_event;
-		ret = blocking_notifier_chain_register(&adp5585->event_notifier,
-						       &adp5585_gpio->nb);
-		if (ret)
-			return ret;
-
-		ret = devm_add_action_or_reset(dev, adp5585_gpio_unreg_notifier,
-					       adp5585_gpio);
+		ret = devm_blocking_notifier_chain_register(dev,
+							    &adp5585->event_notifier,
+							    &adp5585_gpio->nb);
 		if (ret)
 			return ret;
 	}
-- 
2.47.3

[PATCH v5 06/13] platform/x86: bitland-mifs-wmi: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
bitland_notifier_unregister() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
 drivers/platform/x86/bitland-mifs-wmi.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/platform/x86/bitland-mifs-wmi.c b/drivers/platform/x86/bitland-mifs-wmi.c
index 3a373184519d..2bcd4f692a74 100644
--- a/drivers/platform/x86/bitland-mifs-wmi.c
+++ b/drivers/platform/x86/bitland-mifs-wmi.c
@@ -623,13 +623,6 @@ static const struct key_entry bitland_mifs_wmi_keymap[] = {
 	{ KE_END, 0 }
 };
 
-static void bitland_notifier_unregister(void *data)
-{
-	struct notifier_block *nb = data;
-
-	blocking_notifier_chain_unregister(&bitland_notifier_list, nb);
-}
-
 static int bitland_notifier_callback(struct notifier_block *nb,
 				     unsigned long action, void *data)
 {
@@ -729,13 +722,9 @@ static int bitland_mifs_wmi_probe(struct wmi_device *wdev, const void *context)
 		return ret;
 
 	drv_data->notifier.notifier_call = bitland_notifier_callback;
-	ret = blocking_notifier_chain_register(&bitland_notifier_list, &drv_data->notifier);
-	if (ret)
-		return ret;
-
-	return devm_add_action_or_reset(&wdev->dev,
-				       bitland_notifier_unregister,
-				       &drv_data->notifier);
+	return devm_blocking_notifier_chain_register(&wdev->dev,
+						     &bitland_notifier_list,
+						     &drv_data->notifier);
 }
 
 static void bitland_mifs_wmi_notify(struct wmi_device *wdev,
-- 
2.47.3

[PATCH v5 07/13] Input: adp5585: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
adp5585_keys_unreg_notifier() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
---
 drivers/input/keyboard/adp5585-keys.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

diff --git a/drivers/input/keyboard/adp5585-keys.c b/drivers/input/keyboard/adp5585-keys.c
index 017c95029180..0be4cc234c21 100644
--- a/drivers/input/keyboard/adp5585-keys.c
+++ b/drivers/input/keyboard/adp5585-keys.c
@@ -254,15 +254,6 @@ static int adp5585_keys_ev_handle(struct notifier_block *nb, unsigned long key,
 	return NOTIFY_STOP;
 }
 
-static void adp5585_keys_unreg_notifier(void *data)
-{
-	struct adp5585_kpad *kpad = data;
-	struct adp5585_dev *adp5585 = dev_get_drvdata(kpad->dev->parent);
-
-	blocking_notifier_chain_unregister(&adp5585->event_notifier,
-					   &kpad->nb);
-}
-
 static int adp5585_keys_probe(struct platform_device *pdev)
 {
 	const struct platform_device_id *id = platform_get_device_id(pdev);
@@ -318,12 +309,9 @@ static int adp5585_keys_probe(struct platform_device *pdev)
 		return error;
 
 	kpad->nb.notifier_call = adp5585_keys_ev_handle;
-	error = blocking_notifier_chain_register(&adp5585->event_notifier,
-						 &kpad->nb);
-	if (error)
-		return error;
-
-	error = devm_add_action_or_reset(dev, adp5585_keys_unreg_notifier, kpad);
+	error = devm_blocking_notifier_chain_register(dev,
+						      &adp5585->event_notifier,
+						      &kpad->nb);
 	if (error)
 		return error;
 
-- 
2.47.3

[PATCH v5 08/13] ACPI: APEI: GHES: remove unused ghes_{,un}register_vendor_record_notifier()

[Eliav Farber]

Remove ghes_register_vendor_record_notifier() and
ghes_unregister_vendor_record_notifier() along with their
EXPORT_SYMBOL_GPL()s and ghes.h declarations, since there are no
remaining in-tree callers — all users go through
devm_ghes_register_vendor_record_notifier() instead.

Inline the register/unregister calls directly into
devm_ghes_register_vendor_record_notifier() and its destroy callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
Changes in v4:
- Split from the devm conversion patch into its own commit
  (Andy Shevchenko)

Changes in v2:
- New patch: remove unused ghes_register_vendor_record_notifier() and
  ghes_unregister_vendor_record_notifier() along with their
  EXPORT_SYMBOL_GPL()s and ghes.h declarations, since there are no
  in-tree callers (Jonathan Cameron)

 drivers/acpi/apei/ghes.c | 16 +++-------------
 include/acpi/ghes.h      | 16 ----------------
 2 files changed, 3 insertions(+), 29 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 3236a3ce79d6..4e092f71ca84 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -677,29 +677,19 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
 
 static BLOCKING_NOTIFIER_HEAD(vendor_record_notify_list);
 
-int ghes_register_vendor_record_notifier(struct notifier_block *nb)
+static void ghes_vendor_record_notifier_destroy(void *data)
 {
-	return blocking_notifier_chain_register(&vendor_record_notify_list, nb);
-}
-EXPORT_SYMBOL_GPL(ghes_register_vendor_record_notifier);
+	struct notifier_block *nb = data;
 
-void ghes_unregister_vendor_record_notifier(struct notifier_block *nb)
-{
 	blocking_notifier_chain_unregister(&vendor_record_notify_list, nb);
 }
-EXPORT_SYMBOL_GPL(ghes_unregister_vendor_record_notifier);
-
-static void ghes_vendor_record_notifier_destroy(void *nb)
-{
-	ghes_unregister_vendor_record_notifier(nb);
-}
 
 int devm_ghes_register_vendor_record_notifier(struct device *dev,
 					      struct notifier_block *nb)
 {
 	int ret;
 
-	ret = ghes_register_vendor_record_notifier(nb);
+	ret = blocking_notifier_chain_register(&vendor_record_notify_list, nb);
 	if (ret)
 		return ret;
 
diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h
index 8d7e5caef3f1..3cd13171c14f 100644
--- a/include/acpi/ghes.h
+++ b/include/acpi/ghes.h
@@ -55,22 +55,6 @@ enum {
 };
 
 #ifdef CONFIG_ACPI_APEI_GHES
-/**
- * ghes_register_vendor_record_notifier - register a notifier for vendor
- * records that the kernel would otherwise ignore.
- * @nb: pointer to the notifier_block structure of the event handler.
- *
- * return 0 : SUCCESS, non-zero : FAIL
- */
-int ghes_register_vendor_record_notifier(struct notifier_block *nb);
-
-/**
- * ghes_unregister_vendor_record_notifier - unregister the previously
- * registered vendor record notifier.
- * @nb: pointer to the notifier_block structure of the vendor record handler.
- */
-void ghes_unregister_vendor_record_notifier(struct notifier_block *nb);
-
 /**
  * devm_ghes_register_vendor_record_notifier - device-managed vendor
  * record notifier registration.
-- 
2.47.3

[PATCH v5 09/13] ACPI: APEI: GHES: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
ghes_vendor_record_notifier_destroy() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Reviewed-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
Changes in v4:
- Split removal of unused code into a separate preceding patch
  (Andy Shevchenko)

 drivers/acpi/apei/ghes.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 4e092f71ca84..4419d430b7fd 100644
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -677,23 +677,12 @@ static void ghes_handle_aer(struct acpi_hest_generic_data *gdata)
 
 static BLOCKING_NOTIFIER_HEAD(vendor_record_notify_list);
 
-static void ghes_vendor_record_notifier_destroy(void *data)
-{
-	struct notifier_block *nb = data;
-
-	blocking_notifier_chain_unregister(&vendor_record_notify_list, nb);
-}
-
 int devm_ghes_register_vendor_record_notifier(struct device *dev,
 					      struct notifier_block *nb)
 {
-	int ret;
-
-	ret = blocking_notifier_chain_register(&vendor_record_notify_list, nb);
-	if (ret)
-		return ret;
-
-	return devm_add_action_or_reset(dev, ghes_vendor_record_notifier_destroy, nb);
+	return devm_blocking_notifier_chain_register(dev,
+						     &vendor_record_notify_list,
+						     nb);
 }
 EXPORT_SYMBOL_GPL(devm_ghes_register_vendor_record_notifier);
 
-- 
2.47.3

[PATCH v5 10/13] platform/x86: uniwill-wmi: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
devm_uniwill_wmi_unregister_notifier() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
---
 drivers/platform/x86/uniwill/uniwill-wmi.c | 17 +++--------------
 1 file changed, 3 insertions(+), 14 deletions(-)

diff --git a/drivers/platform/x86/uniwill/uniwill-wmi.c b/drivers/platform/x86/uniwill/uniwill-wmi.c
index afcbfa4f7552..2ffa29a829ee 100644
--- a/drivers/platform/x86/uniwill/uniwill-wmi.c
+++ b/drivers/platform/x86/uniwill/uniwill-wmi.c
@@ -26,22 +26,11 @@
 
 static BLOCKING_NOTIFIER_HEAD(uniwill_wmi_chain_head);
 
-static void devm_uniwill_wmi_unregister_notifier(void *data)
-{
-	struct notifier_block *nb = data;
-
-	blocking_notifier_chain_unregister(&uniwill_wmi_chain_head, nb);
-}
-
 int devm_uniwill_wmi_register_notifier(struct device *dev, struct notifier_block *nb)
 {
-	int ret;
-
-	ret = blocking_notifier_chain_register(&uniwill_wmi_chain_head, nb);
-	if (ret < 0)
-		return ret;
-
-	return devm_add_action_or_reset(dev, devm_uniwill_wmi_unregister_notifier, nb);
+	return devm_blocking_notifier_chain_register(dev,
+						     &uniwill_wmi_chain_head,
+						     nb);
 }
 
 static void uniwill_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
-- 
2.47.3

[PATCH v5 11/13] gpio: eic-sprd: use devm_atomic_notifier_chain_register()

[Eliav Farber]

Replace the atomic_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_atomic_notifier_chain_register(), removing the
sprd_eic_unregister_notifier() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
---
 drivers/gpio/gpio-eic-sprd.c | 17 ++---------------
 1 file changed, 2 insertions(+), 15 deletions(-)

diff --git a/drivers/gpio/gpio-eic-sprd.c b/drivers/gpio/gpio-eic-sprd.c
index 3b7ebcf12fe7..86eb9624d38a 100644
--- a/drivers/gpio/gpio-eic-sprd.c
+++ b/drivers/gpio/gpio-eic-sprd.c
@@ -601,13 +601,6 @@ static const struct irq_chip sprd_eic_irq = {
 	GPIOCHIP_IRQ_RESOURCE_HELPERS,
 };
 
-static void sprd_eic_unregister_notifier(void *data)
-{
-	struct notifier_block *nb = data;
-
-	atomic_notifier_chain_unregister(&sprd_eic_irq_notifier, nb);
-}
-
 static int sprd_eic_probe(struct platform_device *pdev)
 {
 	const struct sprd_eic_variant_data *pdata;
@@ -690,14 +683,8 @@ static int sprd_eic_probe(struct platform_device *pdev)
 	}
 
 	sprd_eic->irq_nb.notifier_call = sprd_eic_irq_notify;
-	ret = atomic_notifier_chain_register(&sprd_eic_irq_notifier,
-					     &sprd_eic->irq_nb);
-	if (ret)
-		return dev_err_probe(dev, ret,
-				     "Failed to register with the interrupt notifier");
-
-	return devm_add_action_or_reset(dev, sprd_eic_unregister_notifier,
-					&sprd_eic->irq_nb);
+	return devm_atomic_notifier_chain_register(dev, &sprd_eic_irq_notifier,
+						   &sprd_eic->irq_nb);
 }
 
 static const struct of_device_id sprd_eic_of_match[] = {
-- 
2.47.3

[PATCH v5 12/13] gpio: gpiolib-kunit: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the blocking_notifier_chain_register() +
devm_add_action_or_reset() pattern with a single call to
devm_blocking_notifier_chain_register(), removing the
gpio_unbind_unregister_notifier() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
Acked-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>
---
 drivers/gpio/gpiolib-kunit.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/drivers/gpio/gpiolib-kunit.c b/drivers/gpio/gpiolib-kunit.c
index 380b68f879e5..8ce9acc89e29 100644
--- a/drivers/gpio/gpiolib-kunit.c
+++ b/drivers/gpio/gpiolib-kunit.c
@@ -237,13 +237,6 @@ static int gpio_unbind_notify(struct notifier_block *nb, unsigned long action,
 	return NOTIFY_OK;
 }
 
-static void gpio_unbind_unregister_notifier(void *data)
-{
-	struct notifier_block *nb = data;
-
-	blocking_notifier_chain_unregister(&gpio_unbind_notifier, nb);
-}
-
 static int gpio_unbind_consumer_probe(struct platform_device *pdev)
 {
 	struct gpio_unbind_consumer_drvdata *data;
@@ -261,11 +254,8 @@ static int gpio_unbind_consumer_probe(struct platform_device *pdev)
 		return PTR_ERR(data->desc);
 
 	data->nb.notifier_call = gpio_unbind_notify;
-	ret = blocking_notifier_chain_register(&gpio_unbind_notifier, &data->nb);
-	if (ret)
-		return ret;
-
-	ret = devm_add_action_or_reset(dev, gpio_unbind_unregister_notifier, &data->nb);
+	ret = devm_blocking_notifier_chain_register(dev, &gpio_unbind_notifier,
+						    &data->nb);
 	if (ret)
 		return ret;
 
-- 
2.47.3

[PATCH v5 13/13] reboot: use devm_blocking_notifier_chain_register()

[Eliav Farber]

Replace the manual devres_alloc() + register_reboot_notifier() pattern
with a single call to devm_blocking_notifier_chain_register(), removing
the devm_unregister_reboot_notifier() callback.

Signed-off-by: Eliav Farber <farbere@amazon.com>
---
Changes in v3:
- Fix commit message to accurately describe the old code as using
  devres_alloc() + register_reboot_notifier() (Sashiko)

 kernel/reboot.c | 24 ++----------------------
 1 file changed, 2 insertions(+), 22 deletions(-)

diff --git a/kernel/reboot.c b/kernel/reboot.c
index 695c33e75efd..557609419989 100644
--- a/kernel/reboot.c
+++ b/kernel/reboot.c
@@ -136,30 +136,10 @@ int unregister_reboot_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_reboot_notifier);
 
-static void devm_unregister_reboot_notifier(struct device *dev, void *res)
-{
-	WARN_ON(unregister_reboot_notifier(*(struct notifier_block **)res));
-}
-
 int devm_register_reboot_notifier(struct device *dev, struct notifier_block *nb)
 {
-	struct notifier_block **rcnb;
-	int ret;
-
-	rcnb = devres_alloc(devm_unregister_reboot_notifier,
-			    sizeof(*rcnb), GFP_KERNEL);
-	if (!rcnb)
-		return -ENOMEM;
-
-	ret = register_reboot_notifier(nb);
-	if (!ret) {
-		*rcnb = nb;
-		devres_add(dev, rcnb);
-	} else {
-		devres_free(rcnb);
-	}
-
-	return ret;
+	return devm_blocking_notifier_chain_register(dev,
+						     &reboot_notifier_list, nb);
 }
 EXPORT_SYMBOL(devm_register_reboot_notifier);
 
-- 
2.47.3

Re: [PATCH v5 07/13] Input: adp5585: use devm_blocking_notifier_chain_register()

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] This problem wasn't introduced by this patch, but there is a potential NULL pointer dereference due to an unchecked `platform_get_device_id()` return value.
--

--- Patch [7]: [PATCH v5 07/13] Input: adp5585: use devm_blocking_notifier_chain_register() ---
commit 7fdada2980ba610dca31ca2b97c993a21524a85f
Author: Eliav Farber <farbere@amazon.com>

Input: adp5585: use devm_blocking_notifier_chain_register()

This commit replaces the manual registration and devm cleanup of the
blocking notifier chain with a single call to
devm_blocking_notifier_chain_register().

> diff --git a/drivers/input/keyboard/adp5585-keys.c b/drivers/input/keyboard/adp5585-keys.c
> index 4208229e13561..012558237674e 100644
> --- a/drivers/input/keyboard/adp5585-keys.c
> +++ b/drivers/input/keyboard/adp5585-keys.c
[ ... ]
>  static int adp5585_keys_probe(struct platform_device *pdev)
>  {
>  	const struct platform_device_id *id = platform_get_device_id(pdev);

[Severity: High]
This isn't a bug introduced by this patch, but is it possible for
platform_get_device_id() to return a null pointer here and cause a panic
when id->driver_data is dereferenced?

Looking at adp5585_keys_probe(), the returned id is not checked before
accessing id->driver_data:

drivers/input/keyboard/adp5585-keys.c:adp5585_keys_probe() {
        const struct platform_device_id *id = platform_get_device_id(pdev);
        ...
        kpad->info = (const struct adp5585_kpad_chip *)id->driver_data;
}

If a privileged user writes an arbitrary string to the driver_override
sysfs attribute of a platform device and binds it to this driver,
platform_get_device_id() will return null because the bound device
name doesn't match the driver's id_table. Does this code need a null
pointer check to prevent a local denial of service?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260816060648.4030-1-farbere@amazon.com?part=7

Re: [PATCH v5 05/13] gpio: adp5585: use devm_blocking_notifier_chain_register()

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:

Pre-existing issues:
- [High] The device-managed event notifier is registered before the gpiochip is added, leading to a Use-After-Free of the IRQ domain during device teardown.
--

--- Patch [5]: [PATCH v5 05/13] gpio: adp5585: use devm_blocking_notifier_chain_register() ---
commit c5fe212287473e8e21c8d2bae802d7b8fa665fcd
Author: Eliav Farber <farbere@amazon.com>

gpio: adp5585: use devm_blocking_notifier_chain_register()

This commit replaces the manual registration of a blocking notifier and
its associated devm_add_action_or_reset() cleanup with the new
devm_blocking_notifier_chain_register() helper.

> diff --git a/drivers/gpio/gpio-adp5585.c b/drivers/gpio/gpio-adp5585.c
> index 6f10fc6460080..7c04a7e86c8f8 100644
> --- a/drivers/gpio/gpio-adp5585.c
> +++ b/drivers/gpio/gpio-adp5585.c
[ ... ]
> @@ -450,13 +440,9 @@ static int adp5585_gpio_probe(struct platform_device *pdev)
>  		girq->threaded = true;
>  
>  		adp5585_gpio->nb.notifier_call = adp5585_gpio_key_event;
> -		ret = blocking_notifier_chain_register(&adp5585->event_notifier,
> -						       &adp5585_gpio->nb);
> -		if (ret)
> -			return ret;
> -
> -		ret = devm_add_action_or_reset(dev, adp5585_gpio_unreg_notifier,
> -					       adp5585_gpio);
> +		ret = devm_blocking_notifier_chain_register(dev,
> +							    &adp5585->event_notifier,
> +							    &adp5585_gpio->nb);

[Severity: High]
This is a pre-existing issue, but does this devres registration order
leave a use-after-free window during device unbind?

Because devm_blocking_notifier_chain_register() is called before
devm_gpiochip_add_data() (which happens later in adp5585_gpio_probe),
devres will destroy the gpiochip and its IRQ domain before unregistering
this notifier during device teardown.

If the user unbinds the adp5585-gpio child device via sysfs while the
parent device remains bound, and a hardware interrupt fires on the
parent device during this teardown window, the parent's IRQ handler
executes adp5585_gpio_key_event(). This dereferences the already freed
irq.domain pointer:

adp5585_gpio_key_event() {
	...
	irq = irq_find_mapping(adp5585_gpio->gpio_chip.irq.domain, off);
	...
}

>  		if (ret)
>  			return ret;
>  	}

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260816060648.4030-1-farbere@amazon.com?part=5

Re: [PATCH v5 01/13] notifier: add device-managed registration APIs

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
- [Medium] The patch omits explicitly callable devm_*_unregister() functions, preventing safe early unregistration in drivers.
- [Medium] devm_atomic_notifier_chain_register() is implicitly restricted to process context but its documentation does not state this.
- [Low] Device-managed registration for SRCU notifiers is omitted without justification.
--

--- Patch [1]: [PATCH v5 01/13] notifier: add device-managed registration APIs ---
commit 123931abf8d80f91fce35443259e0df9e2736a4e
Author: Eliav Farber <farbere@amazon.com>

notifier: add device-managed registration APIs

This patch adds devm_atomic_notifier_chain_register() and
devm_blocking_notifier_chain_register() that automatically unregister
the notifier when the device is unbound. This reduces boilerplate in
drivers by eliminating per-driver unregister callbacks.

> diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> index 01b6c9d9956f9..4eeae9741a6e8 100644
> --- a/include/linux/notifier.h
> +++ b/include/linux/notifier.h

[ ... ]

> @@ -145,8 +146,14 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
>  
>  extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
>  		struct notifier_block *nb);
> +int devm_atomic_notifier_chain_register(struct device *dev,
> +		struct atomic_notifier_head *nh,
> +		struct notifier_block *nb);

[Severity: Medium]
Should there be corresponding devm_atomic_notifier_chain_unregister() and
devm_blocking_notifier_chain_unregister() functions provided?

If a driver needs to unregister early to quiesce hardware, manually calling
the non-devm unregister function leaves a stale devres action. This performs
a useless double-unregister during devres_release_all(), which
unconditionally hits the slow synchronize_rcu() and delays unbind.

>  extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
>  		struct notifier_block *nb);
> +int devm_blocking_notifier_chain_register(struct device *dev,
> +		struct blocking_notifier_head *nh,
> +		struct notifier_block *nb);
>  extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
>  		struct notifier_block *nb);
>  extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,

[Severity: Low]
Is there a reason the devm variant for SRCU notifiers was omitted?

The commit message justifies omitting raw notifiers due to locking
constraints, but SRCU notifiers manage their own internal mutex which should
be safe to lock in the devres teardown context.

> diff --git a/kernel/notifier.c b/kernel/notifier.c
> index 2f9fe7c30287f..0c39627ea69c5 100644
> --- a/kernel/notifier.c
> +++ b/kernel/notifier.c

[ ... ]

> @@ -197,6 +198,56 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
>  }
>  EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
>  
> +struct atomic_notifier_chain_devres {
> +	struct atomic_notifier_head *nh;
> +	struct notifier_block *nb;
> +};
> +
> +static void devm_atomic_notifier_chain_unregister(struct device *dev, void *res)
> +{
> +	struct atomic_notifier_chain_devres *dr = res;
> +
> +	atomic_notifier_chain_unregister(dr->nh, dr->nb);
> +}
> +
> +/**
> + *	devm_atomic_notifier_chain_register - Device-managed atomic notifier registration
> + *	@dev: Device to tie the notifier lifetime to
> + *	@nh: Pointer to head of the atomic notifier chain
> + *	@nb: New entry in notifier chain
> + *
> + *	Adds a notifier to an atomic notifier chain and registers a cleanup
> + *	action to automatically unregister it when @dev is unbound.
> + *
> + *	Return:
> + *	0 on success, negative errno on error.
> + */

[Severity: Medium]
Should this kerneldoc include a context warning like "Must be called in
process context."?

Unlike atomic_notifier_chain_register() which is safe in atomic context,
this function uses devres_alloc() with GFP_KERNEL which can sleep, making it
unsafe to call from atomic context.

> +int devm_atomic_notifier_chain_register(struct device *dev,
> +					struct atomic_notifier_head *nh,
> +					struct notifier_block *nb)

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260816060648.4030-1-farbere@amazon.com?part=1

Re: [PATCH v5 01/13] notifier: add device-managed registration APIs

[Uwe Kleine-König]

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Hello Eliav,

On Sun, Aug 16, 2026 at 06:19:06AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 3 potential issue(s) to consider:
> - [Medium] The patch omits explicitly callable devm_*_unregister() functions, preventing safe early unregistration in drivers.
> - [Medium] devm_atomic_notifier_chain_register() is implicitly restricted to process context but its documentation does not state this.
> - [Low] Device-managed registration for SRCU notifiers is omitted without justification.
> --
> 
> --- Patch [1]: [PATCH v5 01/13] notifier: add device-managed registration APIs ---
> commit 123931abf8d80f91fce35443259e0df9e2736a4e
> Author: Eliav Farber <farbere@amazon.com>
> 
> notifier: add device-managed registration APIs
> 
> This patch adds devm_atomic_notifier_chain_register() and
> devm_blocking_notifier_chain_register() that automatically unregister
> the notifier when the device is unbound. This reduces boilerplate in
> drivers by eliminating per-driver unregister callbacks.
> 
> > diff --git a/include/linux/notifier.h b/include/linux/notifier.h
> > index 01b6c9d9956f9..4eeae9741a6e8 100644
> > --- a/include/linux/notifier.h
> > +++ b/include/linux/notifier.h
> 
> [ ... ]
> 
> > @@ -145,8 +146,14 @@ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
> >  
> >  extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
> >  		struct notifier_block *nb);
> > +int devm_atomic_notifier_chain_register(struct device *dev,
> > +		struct atomic_notifier_head *nh,
> > +		struct notifier_block *nb);
> 
> [Severity: Medium]
> Should there be corresponding devm_atomic_notifier_chain_unregister() and
> devm_blocking_notifier_chain_unregister() functions provided?

I think these can be added once they are needed.
 
> If a driver needs to unregister early to quiesce hardware, manually calling
> the non-devm unregister function leaves a stale devres action. This performs
> a useless double-unregister during devres_release_all(), which
> unconditionally hits the slow synchronize_rcu() and delays unbind.
> 
> >  extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
> >  		struct notifier_block *nb);
> > +int devm_blocking_notifier_chain_register(struct device *dev,
> > +		struct blocking_notifier_head *nh,
> > +		struct notifier_block *nb);
> >  extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
> >  		struct notifier_block *nb);
> >  extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
> 
> [Severity: Low]
> Is there a reason the devm variant for SRCU notifiers was omitted?
> 
> The commit message justifies omitting raw notifiers due to locking
> constraints, but SRCU notifiers manage their own internal mutex which should
> be safe to lock in the devres teardown context.

🤷, I don't care much.

> 
> > diff --git a/kernel/notifier.c b/kernel/notifier.c
> > index 2f9fe7c30287f..0c39627ea69c5 100644
> > --- a/kernel/notifier.c
> > +++ b/kernel/notifier.c
> 
> [ ... ]
> 
> > @@ -197,6 +198,56 @@ int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
> >  }
> >  EXPORT_SYMBOL_GPL(atomic_notifier_chain_unregister);
> >  
> > +struct atomic_notifier_chain_devres {
> > +	struct atomic_notifier_head *nh;
> > +	struct notifier_block *nb;
> > +};
> > +
> > +static void devm_atomic_notifier_chain_unregister(struct device *dev, void *res)
> > +{
> > +	struct atomic_notifier_chain_devres *dr = res;
> > +
> > +	atomic_notifier_chain_unregister(dr->nh, dr->nb);
> > +}
> > +
> > +/**
> > + *	devm_atomic_notifier_chain_register - Device-managed atomic notifier registration
> > + *	@dev: Device to tie the notifier lifetime to
> > + *	@nh: Pointer to head of the atomic notifier chain
> > + *	@nb: New entry in notifier chain
> > + *
> > + *	Adds a notifier to an atomic notifier chain and registers a cleanup
> > + *	action to automatically unregister it when @dev is unbound.
> > + *
> > + *	Return:
> > + *	0 on success, negative errno on error.
> > + */
> 
> [Severity: Medium]
> Should this kerneldoc include a context warning like "Must be called in
> process context."?
> 
> Unlike atomic_notifier_chain_register() which is safe in atomic context,
> this function uses devres_alloc() with GFP_KERNEL which can sleep, making it
> unsafe to call from atomic context.

That sounds like a good suggestion.

You didn't specify a merge plan for this series. Given there is no
explicit maintainer for kernel/notifier.c, I can apply patch #1 (with
adding the comment suggested by Sashiko) and provide an immutable branch
for subsystem maintainers to pull into their tree as base to apply their
patches. I'd wait till say Wednesday with that to maybe let reviews
tickle in.

Sounds good?

Best regards
Uwe

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Re: [PATCH v5 01/13] notifier: add device-managed registration APIs

[Uwe Kleine-König]

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Hello,

I already replied to Sashiko's review and only noticed afterwards that
this way most recipients are stripped. So here again for the wide
audience:

I suggested to add "Must be called in process context." to the kdoc for
devm_atomic_notifier_chain_register() as this is a relevant difference
to atomic_notifier_chain_register() and create an immutable branch for
it as a base for subsystems to apply their follow-up patches. I'd wait
till Wednesday for concerns and review tags to tickle in.

Best regards
Uwe

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