[PATCH v6 0/9] devm_led_classdev_register() usage problem

[PATCH v6 0/9] devm_led_classdev_register() usage problem

[George Stark]

This patch series fixes the problem of devm_led_classdev_register misusing.

The basic problem is described in [1]. Shortly when devm_led_classdev_register()
is used then led_classdev_unregister() called after driver's remove() callback.
led_classdev_unregister() calls driver's brightness_set callback and that callback
may use resources which were destroyed already in driver's remove().

After discussion with maintainers [2] [3] we decided:
1) don't touch led subsytem core code and don't remove led_set_brightness() from it
but fix drivers
2) don't use devm_led_classdev_unregister

So the solution is to use devm wrappers for all resources
driver's brightness_set() depends on. And introduce dedicated devm wrapper
for mutex as it's often used resource.

[1] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/
[2] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mc132b9b350fa51931b4fcfe14705d9f06e91421f
[3] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mdbf572a85c33f869a553caf986b6228bb65c8383

Changelog:
v1->v2:
	revise patch series completely

v2->v3:
locking: add define if mutex_destroy() is not an empty function
	new patch, discussed here [8]

devm-helpers: introduce devm_mutex_init
	previous version [4]
	- revise code based on mutex_destroy define
	- update commit message
	- update devm_mutex_init()'s description

leds: aw2013: unlock mutex before destroying it
	previous version [5]
	- make this patch first in the series
	- add tags Fixes and RvB by Andy

leds: aw2013: use devm API to cleanup module's resources
	previous version [6]
	- make aw2013_chip_disable_action()'s body oneline
	- don't shadow devm_mutex_init() return code

leds: aw200xx: use devm API to cleanup module's resources
	previous version [7]
	- make aw200xx_*_action()'s bodies oneline
	- don't shadow devm_mutex_init() return code

leds: lm3532: use devm API to cleanup module's resources
leds: nic78bx: use devm API to cleanup module's resources
leds: mlxreg: use devm_mutex_init for mutex initializtion
leds: an30259a: use devm_mutext_init for mutext initialization
leds: powernv: add LED_RETAIN_AT_SHUTDOWN flag for leds
	- those pathes were planned but not sent in the series #2 due to mail server
	problem on my side. I revised them according to the comments.

v3->v4:
locking: introduce devm_mutex_init
	new patch
	- move devm_mutex_init implementation completely from devm-helpers.h to mutex.h

locking: add define if mutex_destroy() is not an empty function
	drop the patch [9]

devm-helpers: introduce devm_mutex_init
	drop the patch [10]

leds: aw2013: use devm API to cleanup module's resources
	- add tag Tested-by: Nikita Travkin <nikita@trvn.ru>

v4->v5:
leds: aw2013: unlock mutex before destroying it
	merged separately and removed from the series

locking/mutex: move mutex_destroy() definition lower
	introduce optional refactoring patch

locking/mutex: introduce devm_mutex_init
	leave only one devm_mutex_init definition
	add tag Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>

leds* patches
	remove #include <linux/devm-helpers.h> due to devm_mutext_init in mutex.h now

v5->v6:
locking/mutex: move mutex_destroy() definition lower [11]
	drop the patch due to devm_mutex_init block is big enough to be declared standalone.

locking/mutex: introduce devm_mutex_init
	redesign devm_mutex_init function to macro to keep lockdep feature working
	use typeof to redeclare mutex var in macro body (thanks to checkpatch)
	previous version [12]

[4] https://lore.kernel.org/lkml/20231204180603.470421-1-gnstark@salutedevices.com/T/#mf500af0eda2a9ffc95594607dbe4cb64f2e3c9a8
[5] https://lore.kernel.org/lkml/20231204180603.470421-1-gnstark@salutedevices.com/T/#mc92df4fb4f7d4187fb01cc1144acfa5fb5230dd2
[6] https://lore.kernel.org/lkml/20231204180603.470421-1-gnstark@salutedevices.com/T/#m300df89710c43cc2ab598baa16c68dd0a0d7d681
[7] https://lore.kernel.org/lkml/20231204180603.470421-1-gnstark@salutedevices.com/T/#m8e5c65e0c6b137c91fa00bb9320ad581164d1d0b
[8] https://lore.kernel.org/lkml/377e4437-7051-4d88-ae68-1460bcd692e1@redhat.com/T/#m5f84a4a2f387d49678783e652b9e658e02c27450
[9] https://lore.kernel.org/lkml/20231213223020.2713164-1-gnstark@salutedevices.com/T/#m19ad1fc04c560012c1e27418e3156d0c9306dd84
[10] https://lore.kernel.org/lkml/20231213223020.2713164-1-gnstark@salutedevices.com/T/#m63126025f5d1bdcef69bcad50f2e58274d42e2d
[11] https://lore.kernel.org/lkml/20240307024034.1548605-2-gnstark@salutedevices.com/
[12] https://lore.kernel.org/lkml/20240307024034.1548605-3-gnstark@salutedevices.com/

George Stark (9):
  locking/mutex: introduce devm_mutex_init
  leds: aw2013: use devm API to cleanup module's resources
  leds: aw200xx: use devm API to cleanup module's resources
  leds: lp3952: use devm API to cleanup module's resources
  leds: lm3532: use devm API to cleanup module's resources
  leds: nic78bx: use devm API to cleanup module's resources
  leds: mlxreg: use devm_mutex_init for mutex initializtion
  leds: an30259a: use devm_mutext_init for mutext initialization
  leds: powernv: use LED_RETAIN_AT_SHUTDOWN flag for leds

 drivers/leds/leds-an30259a.c | 14 ++++----------
 drivers/leds/leds-aw200xx.c  | 32 +++++++++++++++++++++-----------
 drivers/leds/leds-aw2013.c   | 25 +++++++++++++------------
 drivers/leds/leds-lm3532.c   | 29 +++++++++++++++++------------
 drivers/leds/leds-lp3952.c   | 21 +++++++++++----------
 drivers/leds/leds-mlxreg.c   | 14 +++++---------
 drivers/leds/leds-nic78bx.c  | 23 +++++++++++++----------
 drivers/leds/leds-powernv.c  | 23 ++++++++---------------
 include/linux/mutex.h        | 27 +++++++++++++++++++++++++++
 kernel/locking/mutex-debug.c | 11 +++++++++++
 10 files changed, 130 insertions(+), 89 deletions(-)

--
2.25.1

[PATCH v6 1/9] locking/mutex: introduce devm_mutex_init

[George Stark]

Using of devm API leads to a certain order of releasing resources.
So all dependent resources which are not devm-wrapped should be deleted
with respect to devm-release order. Mutex is one of such objects that
often is bound to other resources and has no own devm wrapping.
Since mutex_destroy() actually does nothing in non-debug builds
frequently calling mutex_destroy() is just ignored which is safe for now
but wrong formally and can lead to a problem if mutex_destroy() will be
extended so introduce devm_mutex_init()

Signed-off-by: George Stark <gnstark@salutedevices.com>
Suggested by-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 include/linux/mutex.h        | 27 +++++++++++++++++++++++++++
 kernel/locking/mutex-debug.c | 11 +++++++++++
 2 files changed, 38 insertions(+)

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 67edc4ca2bee..f57e005ded24 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -22,6 +22,8 @@
 #include <linux/cleanup.h>
 #include <linux/mutex_types.h>
 
+struct device;
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)			\
 		, .dep_map = {					\
@@ -117,6 +119,31 @@ do {							\
 } while (0)
 #endif /* CONFIG_PREEMPT_RT */
 
+#ifdef CONFIG_DEBUG_MUTEXES
+
+int __devm_mutex_init(struct device *dev, struct mutex *lock);
+
+#else
+
+static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+	/*
+	 * When CONFIG_DEBUG_MUTEXES is off mutex_destroy is just a nop so
+	 * no really need to register it in devm subsystem.
+	 */
+	return 0;
+}
+
+#endif
+
+#define devm_mutex_init(dev, mutex)			\
+({							\
+	typeof(mutex) mutex_ = (mutex);			\
+							\
+	mutex_init(mutex_);				\
+	__devm_mutex_init(dev, mutex_);			\
+})
+
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
  * Also see Documentation/locking/mutex-design.rst.
diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
index bc8abb8549d2..6aa77e3dc82e 100644
--- a/kernel/locking/mutex-debug.c
+++ b/kernel/locking/mutex-debug.c
@@ -19,6 +19,7 @@
 #include <linux/kallsyms.h>
 #include <linux/interrupt.h>
 #include <linux/debug_locks.h>
+#include <linux/device.h>
 
 #include "mutex.h"
 
@@ -89,6 +90,16 @@ void debug_mutex_init(struct mutex *lock, const char *name,
 	lock->magic = lock;
 }
 
+static void devm_mutex_release(void *res)
+{
+	mutex_destroy(res);
+}
+
+int __devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
+}
+
 /***
  * mutex_destroy - mark a mutex unusable
  * @lock: the mutex to be destroyed
-- 
2.25.1

[PATCH v6 2/9] leds: aw2013: use devm API to cleanup module's resources

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses resources which were destroyed already
in module's remove() so use devm API instead of remove().

Signed-off-by: George Stark <gnstark@salutedevices.com>
Tested-by: Nikita Travkin <nikita@trvn.ru>
---
 drivers/leds/leds-aw2013.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/leds/leds-aw2013.c b/drivers/leds/leds-aw2013.c
index 17235a5e576a..6475eadcb0df 100644
--- a/drivers/leds/leds-aw2013.c
+++ b/drivers/leds/leds-aw2013.c
@@ -320,6 +320,11 @@ static int aw2013_probe_dt(struct aw2013 *chip)
 	return 0;
 }
 
+static void aw2013_chip_disable_action(void *data)
+{
+	aw2013_chip_disable(data);
+}
+
 static const struct regmap_config aw2013_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
@@ -336,7 +341,10 @@ static int aw2013_probe(struct i2c_client *client)
 	if (!chip)
 		return -ENOMEM;
 
-	mutex_init(&chip->mutex);
+	ret = devm_mutex_init(&client->dev, &chip->mutex);
+	if (ret)
+		return ret;
+
 	mutex_lock(&chip->mutex);
 
 	chip->client = client;
@@ -384,6 +392,10 @@ static int aw2013_probe(struct i2c_client *client)
 		goto error_reg;
 	}
 
+	ret = devm_add_action(&client->dev, aw2013_chip_disable_action, chip);
+	if (ret)
+		goto error_reg;
+
 	ret = aw2013_probe_dt(chip);
 	if (ret < 0)
 		goto error_reg;
@@ -406,19 +418,9 @@ static int aw2013_probe(struct i2c_client *client)
 
 error:
 	mutex_unlock(&chip->mutex);
-	mutex_destroy(&chip->mutex);
 	return ret;
 }
 
-static void aw2013_remove(struct i2c_client *client)
-{
-	struct aw2013 *chip = i2c_get_clientdata(client);
-
-	aw2013_chip_disable(chip);
-
-	mutex_destroy(&chip->mutex);
-}
-
 static const struct of_device_id aw2013_match_table[] = {
 	{ .compatible = "awinic,aw2013", },
 	{ /* sentinel */ },
@@ -432,7 +434,6 @@ static struct i2c_driver aw2013_driver = {
 		.of_match_table = aw2013_match_table,
 	},
 	.probe = aw2013_probe,
-	.remove = aw2013_remove,
 };
 
 module_i2c_driver(aw2013_driver);
-- 
2.25.1

[PATCH v6 3/9] leds: aw200xx: use devm API to cleanup module's resources

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses resources which were destroyed already
in module's remove() so use devm API instead of remove().

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-aw200xx.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/leds/leds-aw200xx.c b/drivers/leds/leds-aw200xx.c
index f584a7f98fc5..5cba52d07b38 100644
--- a/drivers/leds/leds-aw200xx.c
+++ b/drivers/leds/leds-aw200xx.c
@@ -530,6 +530,16 @@ static const struct regmap_config aw200xx_regmap_config = {
 	.disable_locking = true,
 };
 
+static void aw200xx_chip_reset_action(void *data)
+{
+	aw200xx_chip_reset(data);
+}
+
+static void aw200xx_disable_action(void *data)
+{
+	aw200xx_disable(data);
+}
+
 static int aw200xx_probe(struct i2c_client *client)
 {
 	const struct aw200xx_chipdef *cdef;
@@ -568,11 +578,17 @@ static int aw200xx_probe(struct i2c_client *client)
 
 	aw200xx_enable(chip);
 
+	ret = devm_add_action(&client->dev, aw200xx_disable_action, chip);
+	if (ret)
+		return ret;
+
 	ret = aw200xx_chip_check(chip);
 	if (ret)
 		return ret;
 
-	mutex_init(&chip->mutex);
+	ret = devm_mutex_init(&client->dev, &chip->mutex);
+	if (ret)
+		return ret;
 
 	/* Need a lock now since after call aw200xx_probe_fw, sysfs nodes created */
 	mutex_lock(&chip->mutex);
@@ -581,6 +597,10 @@ static int aw200xx_probe(struct i2c_client *client)
 	if (ret)
 		goto out_unlock;
 
+	ret = devm_add_action(&client->dev, aw200xx_chip_reset_action, chip);
+	if (ret)
+		goto out_unlock;
+
 	ret = aw200xx_probe_fw(&client->dev, chip);
 	if (ret)
 		goto out_unlock;
@@ -595,15 +615,6 @@ static int aw200xx_probe(struct i2c_client *client)
 	return ret;
 }
 
-static void aw200xx_remove(struct i2c_client *client)
-{
-	struct aw200xx *chip = i2c_get_clientdata(client);
-
-	aw200xx_chip_reset(chip);
-	aw200xx_disable(chip);
-	mutex_destroy(&chip->mutex);
-}
-
 static const struct aw200xx_chipdef aw20036_cdef = {
 	.channels = 36,
 	.display_size_rows_max = 3,
@@ -652,7 +663,6 @@ static struct i2c_driver aw200xx_driver = {
 		.of_match_table = aw200xx_match_table,
 	},
 	.probe = aw200xx_probe,
-	.remove = aw200xx_remove,
 	.id_table = aw200xx_id,
 };
 module_i2c_driver(aw200xx_driver);
-- 
2.25.1

[PATCH v6 4/9] leds: lp3952: use devm API to cleanup module's resources

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses resources which were destroyed already
in module's remove() so use devm API instead of remove().
Also drop explicit turning LEDs off from remove() due to they will be off
anyway by led_classdev_unregister().

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-lp3952.c | 21 +++++++++++----------
 1 file changed, 11 insertions(+), 10 deletions(-)

diff --git a/drivers/leds/leds-lp3952.c b/drivers/leds/leds-lp3952.c
index 5d18bbfd1f23..e24bfe686312 100644
--- a/drivers/leds/leds-lp3952.c
+++ b/drivers/leds/leds-lp3952.c
@@ -207,6 +207,13 @@ static const struct regmap_config lp3952_regmap = {
 	.cache_type = REGCACHE_MAPLE,
 };
 
+static void gpio_set_low_action(void *data)
+{
+	struct lp3952_led_array *priv = (struct lp3952_led_array *)data;
+
+	gpiod_set_value(priv->enable_gpio, 0);
+}
+
 static int lp3952_probe(struct i2c_client *client)
 {
 	int status;
@@ -226,6 +233,10 @@ static int lp3952_probe(struct i2c_client *client)
 		return status;
 	}
 
+	status = devm_add_action(&client->dev, gpio_set_low_action, priv);
+	if (status)
+		return status;
+
 	priv->regmap = devm_regmap_init_i2c(client, &lp3952_regmap);
 	if (IS_ERR(priv->regmap)) {
 		int err = PTR_ERR(priv->regmap);
@@ -254,15 +265,6 @@ static int lp3952_probe(struct i2c_client *client)
 	return 0;
 }
 
-static void lp3952_remove(struct i2c_client *client)
-{
-	struct lp3952_led_array *priv;
-
-	priv = i2c_get_clientdata(client);
-	lp3952_on_off(priv, LP3952_LED_ALL, false);
-	gpiod_set_value(priv->enable_gpio, 0);
-}
-
 static const struct i2c_device_id lp3952_id[] = {
 	{LP3952_NAME, 0},
 	{}
@@ -274,7 +276,6 @@ static struct i2c_driver lp3952_i2c_driver = {
 			.name = LP3952_NAME,
 	},
 	.probe = lp3952_probe,
-	.remove = lp3952_remove,
 	.id_table = lp3952_id,
 };
 
-- 
2.25.1

[PATCH v6 5/9] leds: lm3532: use devm API to cleanup module's resources

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses resources which were destroyed already
in module's remove() so use devm API instead of remove().

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-lm3532.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/drivers/leds/leds-lm3532.c b/drivers/leds/leds-lm3532.c
index 13662a4aa1f2..aa7966eb506f 100644
--- a/drivers/leds/leds-lm3532.c
+++ b/drivers/leds/leds-lm3532.c
@@ -542,6 +542,13 @@ static int lm3532_parse_als(struct lm3532_data *priv)
 	return ret;
 }
 
+static void gpio_set_low_action(void *data)
+{
+	struct lm3532_data *priv = (struct lm3532_data *)data;
+
+	gpiod_direction_output(priv->enable_gpio, 0);
+}
+
 static int lm3532_parse_node(struct lm3532_data *priv)
 {
 	struct fwnode_handle *child = NULL;
@@ -556,6 +563,12 @@ static int lm3532_parse_node(struct lm3532_data *priv)
 	if (IS_ERR(priv->enable_gpio))
 		priv->enable_gpio = NULL;
 
+	if (priv->enable_gpio) {
+		ret = devm_add_action(&priv->client->dev, gpio_set_low_action, priv);
+		if (ret)
+			return ret;
+	}
+
 	priv->regulator = devm_regulator_get(&priv->client->dev, "vin");
 	if (IS_ERR(priv->regulator))
 		priv->regulator = NULL;
@@ -691,7 +704,10 @@ static int lm3532_probe(struct i2c_client *client)
 		return ret;
 	}
 
-	mutex_init(&drvdata->lock);
+	ret = devm_mutex_init(&client->dev, &drvdata->lock);
+	if (ret)
+		return ret;
+
 	i2c_set_clientdata(client, drvdata);
 
 	ret = lm3532_parse_node(drvdata);
@@ -703,16 +719,6 @@ static int lm3532_probe(struct i2c_client *client)
 	return ret;
 }
 
-static void lm3532_remove(struct i2c_client *client)
-{
-	struct lm3532_data *drvdata = i2c_get_clientdata(client);
-
-	mutex_destroy(&drvdata->lock);
-
-	if (drvdata->enable_gpio)
-		gpiod_direction_output(drvdata->enable_gpio, 0);
-}
-
 static const struct of_device_id of_lm3532_leds_match[] = {
 	{ .compatible = "ti,lm3532", },
 	{},
@@ -727,7 +733,6 @@ MODULE_DEVICE_TABLE(i2c, lm3532_id);
 
 static struct i2c_driver lm3532_i2c_driver = {
 	.probe = lm3532_probe,
-	.remove = lm3532_remove,
 	.id_table = lm3532_id,
 	.driver = {
 		.name = LM3532_NAME,
-- 
2.25.1

[PATCH v6 6/9] leds: nic78bx: use devm API to cleanup module's resources

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses resources which were destroyed already
in module's remove() so use devm API instead of remove().

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-nic78bx.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/leds/leds-nic78bx.c b/drivers/leds/leds-nic78bx.c
index a86b43dd995e..f3049fa14f04 100644
--- a/drivers/leds/leds-nic78bx.c
+++ b/drivers/leds/leds-nic78bx.c
@@ -118,6 +118,15 @@ static struct nic78bx_led nic78bx_leds[] = {
 	}
 };
 
+static void lock_led_reg_action(void *data)
+{
+	struct nic78bx_led_data *led_data = (struct nic78bx_led_data *)data;
+
+	/* Lock LED register */
+	outb(NIC78BX_LOCK_VALUE,
+	     led_data->io_base + NIC78BX_LOCK_REG_OFFSET);
+}
+
 static int nic78bx_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
@@ -152,6 +161,10 @@ static int nic78bx_probe(struct platform_device *pdev)
 	led_data->io_base = io_rc->start;
 	spin_lock_init(&led_data->lock);
 
+	ret = devm_add_action(dev, lock_led_reg_action, led_data);
+	if (ret)
+		return ret;
+
 	for (i = 0; i < ARRAY_SIZE(nic78bx_leds); i++) {
 		nic78bx_leds[i].data = led_data;
 
@@ -167,15 +180,6 @@ static int nic78bx_probe(struct platform_device *pdev)
 	return ret;
 }
 
-static void nic78bx_remove(struct platform_device *pdev)
-{
-	struct nic78bx_led_data *led_data = platform_get_drvdata(pdev);
-
-	/* Lock LED register */
-	outb(NIC78BX_LOCK_VALUE,
-	     led_data->io_base + NIC78BX_LOCK_REG_OFFSET);
-}
-
 static const struct acpi_device_id led_device_ids[] = {
 	{"NIC78B3", 0},
 	{"", 0},
@@ -184,7 +188,6 @@ MODULE_DEVICE_TABLE(acpi, led_device_ids);
 
 static struct platform_driver led_driver = {
 	.probe = nic78bx_probe,
-	.remove_new = nic78bx_remove,
 	.driver = {
 		.name = KBUILD_MODNAME,
 		.acpi_match_table = ACPI_PTR(led_device_ids),
-- 
2.25.1

[PATCH v6 7/9] leds: mlxreg: use devm_mutex_init for mutex initializtion

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses mutex which was destroyed already
in module's remove() so use devm API instead.

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-mlxreg.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/leds/leds-mlxreg.c b/drivers/leds/leds-mlxreg.c
index d8e3d5d8d2d0..b1510cd32e47 100644
--- a/drivers/leds/leds-mlxreg.c
+++ b/drivers/leds/leds-mlxreg.c
@@ -257,6 +257,7 @@ static int mlxreg_led_probe(struct platform_device *pdev)
 {
 	struct mlxreg_core_platform_data *led_pdata;
 	struct mlxreg_led_priv_data *priv;
+	int err;
 
 	led_pdata = dev_get_platdata(&pdev->dev);
 	if (!led_pdata) {
@@ -268,26 +269,21 @@ static int mlxreg_led_probe(struct platform_device *pdev)
 	if (!priv)
 		return -ENOMEM;
 
-	mutex_init(&priv->access_lock);
+	err = devm_mutex_init(&pdev->dev, &priv->access_lock);
+	if (err)
+		return err;
+
 	priv->pdev = pdev;
 	priv->pdata = led_pdata;
 
 	return mlxreg_led_config(priv);
 }
 
-static void mlxreg_led_remove(struct platform_device *pdev)
-{
-	struct mlxreg_led_priv_data *priv = dev_get_drvdata(&pdev->dev);
-
-	mutex_destroy(&priv->access_lock);
-}
-
 static struct platform_driver mlxreg_led_driver = {
 	.driver = {
 	    .name = "leds-mlxreg",
 	},
 	.probe = mlxreg_led_probe,
-	.remove_new = mlxreg_led_remove,
 };
 
 module_platform_driver(mlxreg_led_driver);
-- 
2.25.1

[PATCH v6 8/9] leds: an30259a: use devm_mutext_init for mutext initialization

[George Stark]

In this driver LEDs are registered using devm_led_classdev_register()
so they are automatically unregistered after module's remove() is done.
led_classdev_unregister() calls module's led_set_brightness() to turn off
the LEDs and that callback uses mutex which was destroyed already
in module's remove() so use devm API instead.

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-an30259a.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/leds/leds-an30259a.c b/drivers/leds/leds-an30259a.c
index 0216afed3b6e..decfca447d8a 100644
--- a/drivers/leds/leds-an30259a.c
+++ b/drivers/leds/leds-an30259a.c
@@ -283,7 +283,10 @@ static int an30259a_probe(struct i2c_client *client)
 	if (err < 0)
 		return err;
 
-	mutex_init(&chip->mutex);
+	err = devm_mutex_init(&client->dev, &chip->mutex);
+	if (err)
+		return err;
+
 	chip->client = client;
 	i2c_set_clientdata(client, chip);
 
@@ -317,17 +320,9 @@ static int an30259a_probe(struct i2c_client *client)
 	return 0;
 
 exit:
-	mutex_destroy(&chip->mutex);
 	return err;
 }
 
-static void an30259a_remove(struct i2c_client *client)
-{
-	struct an30259a *chip = i2c_get_clientdata(client);
-
-	mutex_destroy(&chip->mutex);
-}
-
 static const struct of_device_id an30259a_match_table[] = {
 	{ .compatible = "panasonic,an30259a", },
 	{ /* sentinel */ },
@@ -347,7 +342,6 @@ static struct i2c_driver an30259a_driver = {
 		.of_match_table = an30259a_match_table,
 	},
 	.probe = an30259a_probe,
-	.remove = an30259a_remove,
 	.id_table = an30259a_id,
 };
 
-- 
2.25.1

[PATCH v6 9/9] leds: powernv: use LED_RETAIN_AT_SHUTDOWN flag for leds

[George Stark]

This driver wants to keep its LEDs state after module is removed
and implemented it in its own way. LED subsystem supports dedicated
flag LED_RETAIN_AT_SHUTDOWN for the same purpose so use the flag
instead of custom implementation.

Signed-off-by: George Stark <gnstark@salutedevices.com>
---
 drivers/leds/leds-powernv.c | 23 ++++++++---------------
 1 file changed, 8 insertions(+), 15 deletions(-)

diff --git a/drivers/leds/leds-powernv.c b/drivers/leds/leds-powernv.c
index 4f01acb75727..9c6fb7d6e0e7 100644
--- a/drivers/leds/leds-powernv.c
+++ b/drivers/leds/leds-powernv.c
@@ -30,15 +30,6 @@ static const struct led_type_map led_type_map[] = {
 };
 
 struct powernv_led_common {
-	/*
-	 * By default unload path resets all the LEDs. But on PowerNV
-	 * platform we want to retain LED state across reboot as these
-	 * are controlled by firmware. Also service processor can modify
-	 * the LEDs independent of OS. Hence avoid resetting LEDs in
-	 * unload path.
-	 */
-	bool		led_disabled;
-
 	/* Max supported LED type */
 	__be64		max_led_type;
 
@@ -178,10 +169,6 @@ static int powernv_brightness_set(struct led_classdev *led_cdev,
 	struct powernv_led_common *powernv_led_common = powernv_led->common;
 	int rc;
 
-	/* Do not modify LED in unload path */
-	if (powernv_led_common->led_disabled)
-		return 0;
-
 	mutex_lock(&powernv_led_common->lock);
 	rc = powernv_led_set(powernv_led, value);
 	mutex_unlock(&powernv_led_common->lock);
@@ -225,6 +212,14 @@ static int powernv_led_create(struct device *dev,
 
 	powernv_led->cdev.brightness_set_blocking = powernv_brightness_set;
 	powernv_led->cdev.brightness_get = powernv_brightness_get;
+	/*
+	 * By default unload path resets all the LEDs. But on PowerNV
+	 * platform we want to retain LED state across reboot as these
+	 * are controlled by firmware. Also service processor can modify
+	 * the LEDs independent of OS. Hence avoid resetting LEDs in
+	 * unload path.
+	 */
+	powernv_led->cdev.flags = LED_RETAIN_AT_SHUTDOWN;
 	powernv_led->cdev.brightness = LED_OFF;
 	powernv_led->cdev.max_brightness = LED_FULL;
 
@@ -313,9 +308,7 @@ static void powernv_led_remove(struct platform_device *pdev)
 {
 	struct powernv_led_common *powernv_led_common;
 
-	/* Disable LED operation */
 	powernv_led_common = platform_get_drvdata(pdev);
-	powernv_led_common->led_disabled = true;
 
 	/* Destroy lock */
 	mutex_destroy(&powernv_led_common->lock);
-- 
2.25.1

Re: [PATCH v6 1/9] locking/mutex: introduce devm_mutex_init

[Christophe Leroy]

Le 14/03/2024 à 09:45, George Stark a écrit :
> Using of devm API leads to a certain order of releasing resources.
> So all dependent resources which are not devm-wrapped should be deleted
> with respect to devm-release order. Mutex is one of such objects that
> often is bound to other resources and has no own devm wrapping.
> Since mutex_destroy() actually does nothing in non-debug builds
> frequently calling mutex_destroy() is just ignored which is safe for now
> but wrong formally and can lead to a problem if mutex_destroy() will be
> extended so introduce devm_mutex_init()
> 
> Signed-off-by: George Stark <gnstark@salutedevices.com>
> Suggested by-by: Christophe Leroy <christophe.leroy@csgroup.eu>

s/Suggested by-by/Suggested-by:

Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>

> ---
>   include/linux/mutex.h        | 27 +++++++++++++++++++++++++++
>   kernel/locking/mutex-debug.c | 11 +++++++++++
>   2 files changed, 38 insertions(+)
> 
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 67edc4ca2bee..f57e005ded24 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -22,6 +22,8 @@
>   #include <linux/cleanup.h>
>   #include <linux/mutex_types.h>
>   
> +struct device;
> +
>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
>   # define __DEP_MAP_MUTEX_INITIALIZER(lockname)			\
>   		, .dep_map = {					\
> @@ -117,6 +119,31 @@ do {							\
>   } while (0)
>   #endif /* CONFIG_PREEMPT_RT */
>   
> +#ifdef CONFIG_DEBUG_MUTEXES
> +
> +int __devm_mutex_init(struct device *dev, struct mutex *lock);
> +
> +#else
> +
> +static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> +	/*
> +	 * When CONFIG_DEBUG_MUTEXES is off mutex_destroy is just a nop so
> +	 * no really need to register it in devm subsystem.
> +	 */
> +	return 0;
> +}
> +
> +#endif
> +
> +#define devm_mutex_init(dev, mutex)			\
> +({							\
> +	typeof(mutex) mutex_ = (mutex);			\
> +							\
> +	mutex_init(mutex_);				\
> +	__devm_mutex_init(dev, mutex_);			\
> +})
> +
>   /*
>    * See kernel/locking/mutex.c for detailed documentation of these APIs.
>    * Also see Documentation/locking/mutex-design.rst.
> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
> index bc8abb8549d2..6aa77e3dc82e 100644
> --- a/kernel/locking/mutex-debug.c
> +++ b/kernel/locking/mutex-debug.c
> @@ -19,6 +19,7 @@
>   #include <linux/kallsyms.h>
>   #include <linux/interrupt.h>
>   #include <linux/debug_locks.h>
> +#include <linux/device.h>
>   
>   #include "mutex.h"
>   
> @@ -89,6 +90,16 @@ void debug_mutex_init(struct mutex *lock, const char *name,
>   	lock->magic = lock;
>   }
>   
> +static void devm_mutex_release(void *res)
> +{
> +	mutex_destroy(res);
> +}
> +
> +int __devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> +	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> +}
> +
>   /***
>    * mutex_destroy - mark a mutex unusable
>    * @lock: the mutex to be destroyed

Re: [PATCH v6 1/9] locking/mutex: introduce devm_mutex_init

[Andy Shevchenko]

On Thu, Mar 14, 2024 at 10:46 AM George Stark <gnstark@salutedevices.com> wrote:
>
> Using of devm API leads to a certain order of releasing resources.
> So all dependent resources which are not devm-wrapped should be deleted
> with respect to devm-release order. Mutex is one of such objects that
> often is bound to other resources and has no own devm wrapping.
> Since mutex_destroy() actually does nothing in non-debug builds
> frequently calling mutex_destroy() is just ignored which is safe for now
> but wrong formally and can lead to a problem if mutex_destroy() will be
> extended so introduce devm_mutex_init()

Missing period at the end.

....

> Suggested by-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Needs properly spelled tag.

...

> +static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> +       /*
> +        * When CONFIG_DEBUG_MUTEXES is off mutex_destroy is just a nop so

mutex_destroy()

> +        * no really need to register it in devm subsystem.

in the devm

> +        */
> +       return 0;
> +}

...

> @@ -19,6 +19,7 @@
>  #include <linux/kallsyms.h>
>  #include <linux/interrupt.h>
>  #include <linux/debug_locks.h>
> +#include <linux/device.h>

Without seeing much context can't say if there is a better (more
ordered) place to squeeze a new header to. Please, check.

...

After addressing the above comments
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 9/9] leds: powernv: use LED_RETAIN_AT_SHUTDOWN flag for leds

[Andy Shevchenko]

On Thu, Mar 14, 2024 at 10:46 AM George Stark <gnstark@salutedevices.com> wrote:
>
> This driver wants to keep its LEDs state after module is removed
> and implemented it in its own way. LED subsystem supports dedicated
> flag LED_RETAIN_AT_SHUTDOWN for the same purpose so use the flag
> instead of custom implementation.

So, this change is not related to the main purpose of the series...

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 0/9] devm_led_classdev_register() usage problem

[Andy Shevchenko]

On Thu, Mar 14, 2024 at 10:46 AM George Stark <gnstark@salutedevices.com> wrote:
>
> This patch series fixes the problem of devm_led_classdev_register misusing.
>
> The basic problem is described in [1]. Shortly when devm_led_classdev_register()
> is used then led_classdev_unregister() called after driver's remove() callback.
> led_classdev_unregister() calls driver's brightness_set callback and that callback
> may use resources which were destroyed already in driver's remove().
>
> After discussion with maintainers [2] [3] we decided:
> 1) don't touch led subsytem core code and don't remove led_set_brightness() from it

subsystem

> but fix drivers
> 2) don't use devm_led_classdev_unregister
>
> So the solution is to use devm wrappers for all resources
> driver's brightness_set() depends on. And introduce dedicated devm wrapper
> for mutex as it's often used resource.

The leds related changes (except the last one) LGTM, hence FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
(for patches 2-8)

> [1] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/
> [2] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mc132b9b350fa51931b4fcfe14705d9f06e91421f
> [3] https://lore.kernel.org/lkml/8704539b-ed3b-44e6-aa82-586e2f895e2b@salutedevices.com/T/#mdbf572a85c33f869a553caf986b6228bb65c8383

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH v6 1/9] locking/mutex: introduce devm_mutex_init

[Marek Behún]

On Thu, 14 Mar 2024 11:45:23 +0300
George Stark <gnstark@salutedevices.com> wrote:

> Using of devm API leads to a certain order of releasing resources.
> So all dependent resources which are not devm-wrapped should be deleted
> with respect to devm-release order. Mutex is one of such objects that
> often is bound to other resources and has no own devm wrapping.
> Since mutex_destroy() actually does nothing in non-debug builds
> frequently calling mutex_destroy() is just ignored which is safe for now
> but wrong formally and can lead to a problem if mutex_destroy() will be
> extended so introduce devm_mutex_init()
> 
> Signed-off-by: George Stark <gnstark@salutedevices.com>
> Suggested by-by: Christophe Leroy <christophe.leroy@csgroup.eu>

Reviewed-by: Marek Behún <kabel@kernel.org>

Re: [PATCH v6 1/9] locking/mutex: introduce devm_mutex_init

[Waiman Long]

On 3/14/24 04:45, George Stark wrote:
> Using of devm API leads to a certain order of releasing resources.
> So all dependent resources which are not devm-wrapped should be deleted
> with respect to devm-release order. Mutex is one of such objects that
> often is bound to other resources and has no own devm wrapping.
> Since mutex_destroy() actually does nothing in non-debug builds
> frequently calling mutex_destroy() is just ignored which is safe for now
> but wrong formally and can lead to a problem if mutex_destroy() will be
> extended so introduce devm_mutex_init()
>
> Signed-off-by: George Stark <gnstark@salutedevices.com>
> Suggested by-by: Christophe Leroy <christophe.leroy@csgroup.eu>
> ---
>   include/linux/mutex.h        | 27 +++++++++++++++++++++++++++
>   kernel/locking/mutex-debug.c | 11 +++++++++++
>   2 files changed, 38 insertions(+)
>
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index 67edc4ca2bee..f57e005ded24 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -22,6 +22,8 @@
>   #include <linux/cleanup.h>
>   #include <linux/mutex_types.h>
>   
> +struct device;
> +
>   #ifdef CONFIG_DEBUG_LOCK_ALLOC
>   # define __DEP_MAP_MUTEX_INITIALIZER(lockname)			\
>   		, .dep_map = {					\
> @@ -117,6 +119,31 @@ do {							\
>   } while (0)
>   #endif /* CONFIG_PREEMPT_RT */
>   
> +#ifdef CONFIG_DEBUG_MUTEXES
> +
> +int __devm_mutex_init(struct device *dev, struct mutex *lock);
> +
> +#else
> +
> +static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> +	/*
> +	 * When CONFIG_DEBUG_MUTEXES is off mutex_destroy is just a nop so
> +	 * no really need to register it in devm subsystem.
> +	 */
> +	return 0;
> +}
> +
> +#endif
> +
> +#define devm_mutex_init(dev, mutex)			\
> +({							\
> +	typeof(mutex) mutex_ = (mutex);			\
> +							\
> +	mutex_init(mutex_);				\
> +	__devm_mutex_init(dev, mutex_);			\
> +})
> +
>   /*
>    * See kernel/locking/mutex.c for detailed documentation of these APIs.
>    * Also see Documentation/locking/mutex-design.rst.
> diff --git a/kernel/locking/mutex-debug.c b/kernel/locking/mutex-debug.c
> index bc8abb8549d2..6aa77e3dc82e 100644
> --- a/kernel/locking/mutex-debug.c
> +++ b/kernel/locking/mutex-debug.c
> @@ -19,6 +19,7 @@
>   #include <linux/kallsyms.h>
>   #include <linux/interrupt.h>
>   #include <linux/debug_locks.h>
> +#include <linux/device.h>
>   
>   #include "mutex.h"
>   
> @@ -89,6 +90,16 @@ void debug_mutex_init(struct mutex *lock, const char *name,
>   	lock->magic = lock;
>   }
>   
> +static void devm_mutex_release(void *res)
> +{
> +	mutex_destroy(res);
> +}
> +
> +int __devm_mutex_init(struct device *dev, struct mutex *lock)
> +{
> +	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
> +}
> +
>   /***
>    * mutex_destroy - mark a mutex unusable
>    * @lock: the mutex to be destroyed
Acked-by: Waiman Long <longman@redhat.com>