Various drivers, mostly in platform/x86 extend the ACPI battery driver
with additional sysfs attributes to implement more UAPIs than are
exposed through ACPI by using various side-channels, like WMI,
nonstandard ACPI or EC communication.

While the created sysfs attributes look similar to the attributes
provided by the powersupply core, there are various deficiencies:

* They don't show up in uevent payload.
* They can't be queried with the standard in-kernel APIs.
* They don't work with triggers.
* The extending driver has to reimplement all of the parsing,
formatting and sysfs display logic.
* Writing a extension driver is completely different from writing a
normal power supply driver.

This extension API avoids all of these issues.
An extension is just a "struct power_supply_ext" with the same kind of
callbacks as in a normal "struct power_supply_desc".

The API is meant to be used via battery_hook_register(), the same way as
the current extensions.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
---
 drivers/power/supply/power_supply.h       |  17 ++++
 drivers/power/supply/power_supply_core.c  | 162 ++++++++++++++++++++++++++++--
 drivers/power/supply/power_supply_sysfs.c |  26 ++++-
 include/linux/power_supply.h              |  33 ++++++
 4 files changed, 228 insertions(+), 10 deletions(-)

diff --git a/drivers/power/supply/power_supply.h b/drivers/power/supply/power_supply.h
index 5dabbd895538003096b62d03fdd0201b82b090e6..531785516d2ac31f9a7f73a58e15e64cb81820ed 100644
--- a/drivers/power/supply/power_supply.h
+++ b/drivers/power/supply/power_supply.h
@@ -9,6 +9,8 @@
  *  Modified: 2004, Oct     Szabolcs Gyurko
  */
 
+#include <linux/lockdep.h>
+
 struct device;
 struct device_type;
 struct power_supply;
@@ -17,6 +19,21 @@ extern int power_supply_property_is_writeable(struct power_supply *psy,
 					      enum power_supply_property psp);
 extern bool power_supply_has_property(struct power_supply *psy,
 				      enum power_supply_property psp);
+extern bool power_supply_ext_has_property(const struct power_supply_ext *ext,
+					  enum power_supply_property psp);
+
+struct power_supply_ext_registration {
+	struct list_head list_head;
+	const struct power_supply_ext *ext;
+	void *data;
+};
+
+/* Make sure that the macro is a single expression */
+#define power_supply_for_each_extension(pos, psy)			\
+	if ( ({ lockdep_assert_held(&(psy)->extensions_sem); 0; }) )	\
+		;							\
+	else								\
+		list_for_each_entry(pos, &(psy)->extensions, list_head)	\
 
 #ifdef CONFIG_SYSFS
 
diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index 502b07468b93dfb7f5a6c2092588d931a7d015f2..bc22edbd0e6a02c27500132075f5c98d814a7330 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -81,6 +81,7 @@ static int __power_supply_changed_work(struct device *dev, void *data)
 
 static void power_supply_changed_work(struct work_struct *work)
 {
+	int ret;
 	unsigned long flags;
 	struct power_supply *psy = container_of(work, struct power_supply,
 						changed_work);
@@ -88,6 +89,16 @@ static void power_supply_changed_work(struct work_struct *work)
 	dev_dbg(&psy->dev, "%s\n", __func__);
 
 	spin_lock_irqsave(&psy->changed_lock, flags);
+
+	if (unlikely(psy->update_groups)) {
+		psy->update_groups = false;
+		spin_unlock_irqrestore(&psy->changed_lock, flags);
+		ret = sysfs_update_groups(&psy->dev.kobj, power_supply_dev_type.groups);
+		if (ret)
+			dev_warn(&psy->dev, "failed to update sysfs groups: %pe\n", ERR_PTR(ret));
+		spin_lock_irqsave(&psy->changed_lock, flags);
+	}
+
 	/*
 	 * Check 'changed' here to avoid issues due to race between
 	 * power_supply_changed() and this routine. In worst case
@@ -1196,15 +1207,34 @@ static bool psy_desc_has_property(const struct power_supply_desc *psy_desc,
 	return found;
 }
 
+bool power_supply_ext_has_property(const struct power_supply_ext *psy_ext,
+				   enum power_supply_property psp)
+{
+	int i;
+
+	for (i = 0; i < psy_ext->num_properties; i++)
+		if (psy_ext->properties[i] == psp)
+			return true;
+
+	return false;
+}
+
 bool power_supply_has_property(struct power_supply *psy,
 			       enum power_supply_property psp)
 {
+	struct power_supply_ext_registration *reg;
+
 	if (psy_desc_has_property(psy->desc, psp))
 		return true;
 
 	if (power_supply_battery_info_has_prop(psy->battery_info, psp))
 		return true;
 
+	power_supply_for_each_extension(reg, psy) {
+		if (power_supply_ext_has_property(reg->ext, psp))
+			return true;
+	}
+
 	return false;
 }
 
@@ -1212,12 +1242,21 @@ int power_supply_get_property(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    union power_supply_propval *val)
 {
+	struct power_supply_ext_registration *reg;
+
 	if (atomic_read(&psy->use_cnt) <= 0) {
 		if (!psy->initialized)
 			return -EAGAIN;
 		return -ENODEV;
 	}
 
+	scoped_guard(rwsem_read, &psy->extensions_sem) {
+		power_supply_for_each_extension(reg, psy) {
+			if (power_supply_ext_has_property(reg->ext, psp))
+				return reg->ext->get_property(psy, reg->ext, reg->data, psp, val);
+		}
+	}
+
 	if (psy_desc_has_property(psy->desc, psp))
 		return psy->desc->get_property(psy, psp, val);
 	else if (power_supply_battery_info_has_prop(psy->battery_info, psp))
@@ -1231,7 +1270,24 @@ int power_supply_set_property(struct power_supply *psy,
 			    enum power_supply_property psp,
 			    const union power_supply_propval *val)
 {
-	if (atomic_read(&psy->use_cnt) <= 0 || !psy->desc->set_property)
+	struct power_supply_ext_registration *reg;
+
+	if (atomic_read(&psy->use_cnt) <= 0)
+		return -ENODEV;
+
+	scoped_guard(rwsem_read, &psy->extensions_sem) {
+		power_supply_for_each_extension(reg, psy) {
+			if (power_supply_ext_has_property(reg->ext, psp)) {
+				if (reg->ext->set_property)
+					return reg->ext->set_property(psy, reg->ext, reg->data,
+								      psp, val);
+				else
+					return -ENODEV;
+			}
+		}
+	}
+
+	if (!psy->desc->set_property)
 		return -ENODEV;
 
 	return psy->desc->set_property(psy, psp, val);
@@ -1241,7 +1297,22 @@ EXPORT_SYMBOL_GPL(power_supply_set_property);
 int power_supply_property_is_writeable(struct power_supply *psy,
 					enum power_supply_property psp)
 {
-	return psy->desc->property_is_writeable && psy->desc->property_is_writeable(psy, psp);
+	struct power_supply_ext_registration *reg;
+
+	power_supply_for_each_extension(reg, psy) {
+		if (power_supply_ext_has_property(reg->ext, psp)) {
+			if (reg->ext->property_is_writeable)
+				return reg->ext->property_is_writeable(psy, reg->ext,
+								       reg->data, psp);
+			else
+				return 0;
+		}
+	}
+
+	if (!psy->desc->property_is_writeable)
+		return 0;
+
+	return psy->desc->property_is_writeable(psy, psp);
 }
 
 void power_supply_external_power_changed(struct power_supply *psy)
@@ -1260,6 +1331,76 @@ int power_supply_powers(struct power_supply *psy, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(power_supply_powers);
 
+static int power_supply_update_sysfs_and_hwmon(struct power_supply *psy)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&psy->changed_lock, flags);
+	psy->update_groups = true;
+	spin_unlock_irqrestore(&psy->changed_lock, flags);
+
+	power_supply_changed(psy);
+
+	power_supply_remove_hwmon_sysfs(psy);
+	return power_supply_add_hwmon_sysfs(psy);
+}
+
+int power_supply_register_extension(struct power_supply *psy, const struct power_supply_ext *ext,
+				    void *data)
+{
+	struct power_supply_ext_registration *reg;
+	size_t i;
+	int ret;
+
+	if (!psy || !ext || !ext->properties || !ext->num_properties)
+		return -EINVAL;
+
+	guard(rwsem_write)(&psy->extensions_sem);
+
+	for (i = 0; i < ext->num_properties; i++)
+		if (power_supply_has_property(psy, ext->properties[i]))
+			return -EEXIST;
+
+	reg = kmalloc(sizeof(*reg), GFP_KERNEL);
+	if (!reg)
+		return -ENOMEM;
+
+	reg->ext = ext;
+	reg->data = data;
+	list_add(&reg->list_head, &psy->extensions);
+
+	ret = power_supply_update_sysfs_and_hwmon(psy);
+	if (ret)
+		goto sysfs_hwmon_failed;
+
+	return 0;
+
+sysfs_hwmon_failed:
+	list_del(&reg->list_head);
+	kfree(reg);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(power_supply_register_extension);
+
+void power_supply_unregister_extension(struct power_supply *psy, const struct power_supply_ext *ext)
+{
+	struct power_supply_ext_registration *reg;
+
+	guard(rwsem_write)(&psy->extensions_sem);
+
+	power_supply_for_each_extension(reg, psy) {
+		if (reg->ext == ext) {
+			list_del(&reg->list_head);
+			kfree(reg);
+			power_supply_update_sysfs_and_hwmon(psy);
+			return;
+		}
+	}
+
+	dev_warn(&psy->dev, "Trying to unregister invalid extension");
+}
+EXPORT_SYMBOL_GPL(power_supply_unregister_extension);
+
 static void power_supply_dev_release(struct device *dev)
 {
 	struct power_supply *psy = to_power_supply(dev);
@@ -1414,6 +1555,9 @@ __power_supply_register(struct device *parent,
 	}
 
 	spin_lock_init(&psy->changed_lock);
+	init_rwsem(&psy->extensions_sem);
+	INIT_LIST_HEAD(&psy->extensions);
+
 	rc = device_add(dev);
 	if (rc)
 		goto device_add_failed;
@@ -1426,13 +1570,15 @@ __power_supply_register(struct device *parent,
 	if (rc)
 		goto register_thermal_failed;
 
-	rc = power_supply_create_triggers(psy);
-	if (rc)
-		goto create_triggers_failed;
+	scoped_guard(rwsem_read, &psy->extensions_sem) {
+		rc = power_supply_create_triggers(psy);
+		if (rc)
+			goto create_triggers_failed;
 
-	rc = power_supply_add_hwmon_sysfs(psy);
-	if (rc)
-		goto add_hwmon_sysfs_failed;
+		rc = power_supply_add_hwmon_sysfs(psy);
+		if (rc)
+			goto add_hwmon_sysfs_failed;
+	}
 
 	/*
 	 * Update use_cnt after any uevents (most notably from device_add()).
diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
index 99bfe1f03eb8326d38c4e2831c9670313b42e425..927ddb9d83bb7259809ba695cb9398d1ad654b46 100644
--- a/drivers/power/supply/power_supply_sysfs.c
+++ b/drivers/power/supply/power_supply_sysfs.c
@@ -268,6 +268,27 @@ static ssize_t power_supply_show_enum_with_available(
 	return count;
 }
 
+static ssize_t power_supply_show_charge_behaviour(struct device *dev,
+						  struct power_supply *psy,
+						  union power_supply_propval *value,
+						  char *buf)
+{
+	struct power_supply_ext_registration *reg;
+
+	scoped_guard(rwsem_read, &psy->extensions_sem) {
+		power_supply_for_each_extension(reg, psy) {
+			if (power_supply_ext_has_property(reg->ext,
+							  POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR))
+				return power_supply_charge_behaviour_show(dev,
+						reg->ext->charge_behaviours,
+						value->intval, buf);
+		}
+	}
+
+	return power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
+						  value->intval, buf);
+}
+
 static ssize_t power_supply_format_property(struct device *dev,
 					    bool uevent,
 					    struct device_attribute *attr,
@@ -307,8 +328,7 @@ static ssize_t power_supply_format_property(struct device *dev,
 	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
 		if (uevent) /* no possible values in uevents */
 			goto default_format;
-		ret = power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
-							 value.intval, buf);
+		ret = power_supply_show_charge_behaviour(dev, psy, &value, buf);
 		break;
 	case POWER_SUPPLY_PROP_MODEL_NAME ... POWER_SUPPLY_PROP_SERIAL_NUMBER:
 		ret = sysfs_emit(buf, "%s\n", value.strval);
@@ -385,6 +405,8 @@ static umode_t power_supply_attr_is_visible(struct kobject *kobj,
 	if (attrno == POWER_SUPPLY_PROP_TYPE)
 		return mode;
 
+	guard(rwsem_read)(&psy->extensions_sem);
+
 	if (power_supply_has_property(psy, attrno)) {
 		if (power_supply_property_is_writeable(psy, attrno) > 0)
 			mode |= S_IWUSR;
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index b98106e1a90f34bce5129317a099f363248342b9..e434516086f032cdb4698005bb1a99eda303a307 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -15,6 +15,8 @@
 #include <linux/device.h>
 #include <linux/workqueue.h>
 #include <linux/leds.h>
+#include <linux/rwsem.h>
+#include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/notifier.h>
 
@@ -281,6 +283,27 @@ struct power_supply_desc {
 	int use_for_apm;
 };
 
+struct power_supply_ext {
+	u8 charge_behaviours;
+	const enum power_supply_property *properties;
+	size_t num_properties;
+
+	int (*get_property)(struct power_supply *psy,
+			    const struct power_supply_ext *ext,
+			    void *data,
+			    enum power_supply_property psp,
+			    union power_supply_propval *val);
+	int (*set_property)(struct power_supply *psy,
+			    const struct power_supply_ext *ext,
+			    void *data,
+			    enum power_supply_property psp,
+			    const union power_supply_propval *val);
+	int (*property_is_writeable)(struct power_supply *psy,
+				     const struct power_supply_ext *ext,
+				     void *data,
+				     enum power_supply_property psp);
+};
+
 struct power_supply {
 	const struct power_supply_desc *desc;
 
@@ -300,10 +323,13 @@ struct power_supply {
 	struct delayed_work deferred_register_work;
 	spinlock_t changed_lock;
 	bool changed;
+	bool update_groups;
 	bool initialized;
 	bool removing;
 	atomic_t use_cnt;
 	struct power_supply_battery_info *battery_info;
+	struct rw_semaphore extensions_sem; /* protects "extensions" */
+	struct list_head extensions;
 #ifdef CONFIG_THERMAL
 	struct thermal_zone_device *tzd;
 	struct thermal_cooling_device *tcd;
@@ -878,6 +904,13 @@ devm_power_supply_register(struct device *parent,
 extern void power_supply_unregister(struct power_supply *psy);
 extern int power_supply_powers(struct power_supply *psy, struct device *dev);
 
+extern int __must_check
+power_supply_register_extension(struct power_supply *psy,
+				const struct power_supply_ext *ext,
+				void *data);
+extern void power_supply_unregister_extension(struct power_supply *psy,
+					      const struct power_supply_ext *ext);
+
 #define to_power_supply(device) container_of(device, struct power_supply, dev)
 
 extern void *power_supply_get_drvdata(struct power_supply *psy);

-- 
2.47.1

Am 11.12.24 um 20:57 schrieb Thomas Weißschuh:

> Various drivers, mostly in platform/x86 extend the ACPI battery driver
> with additional sysfs attributes to implement more UAPIs than are
> exposed through ACPI by using various side-channels, like WMI,
> nonstandard ACPI or EC communication.
>
> While the created sysfs attributes look similar to the attributes
> provided by the powersupply core, there are various deficiencies:
>
> * They don't show up in uevent payload.
> * They can't be queried with the standard in-kernel APIs.
> * They don't work with triggers.
> * The extending driver has to reimplement all of the parsing,
> formatting and sysfs display logic.
> * Writing a extension driver is completely different from writing a
> normal power supply driver.
>
> This extension API avoids all of these issues.
> An extension is just a "struct power_supply_ext" with the same kind of
> callbacks as in a normal "struct power_supply_desc".
>
> The API is meant to be used via battery_hook_register(), the same way as
> the current extensions.

Reviewed-by: Armin Wolf <W_Armin@gmx.de>

> Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
> ---
>   drivers/power/supply/power_supply.h       |  17 ++++
>   drivers/power/supply/power_supply_core.c  | 162 ++++++++++++++++++++++++++++--
>   drivers/power/supply/power_supply_sysfs.c |  26 ++++-
>   include/linux/power_supply.h              |  33 ++++++
>   4 files changed, 228 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/power/supply/power_supply.h b/drivers/power/supply/power_supply.h
> index 5dabbd895538003096b62d03fdd0201b82b090e6..531785516d2ac31f9a7f73a58e15e64cb81820ed 100644
> --- a/drivers/power/supply/power_supply.h
> +++ b/drivers/power/supply/power_supply.h
> @@ -9,6 +9,8 @@
>    *  Modified: 2004, Oct     Szabolcs Gyurko
>    */
>
> +#include <linux/lockdep.h>
> +
>   struct device;
>   struct device_type;
>   struct power_supply;
> @@ -17,6 +19,21 @@ extern int power_supply_property_is_writeable(struct power_supply *psy,
>   					      enum power_supply_property psp);
>   extern bool power_supply_has_property(struct power_supply *psy,
>   				      enum power_supply_property psp);
> +extern bool power_supply_ext_has_property(const struct power_supply_ext *ext,
> +					  enum power_supply_property psp);
> +
> +struct power_supply_ext_registration {
> +	struct list_head list_head;
> +	const struct power_supply_ext *ext;
> +	void *data;
> +};
> +
> +/* Make sure that the macro is a single expression */
> +#define power_supply_for_each_extension(pos, psy)			\
> +	if ( ({ lockdep_assert_held(&(psy)->extensions_sem); 0; }) )	\
> +		;							\
> +	else								\
> +		list_for_each_entry(pos, &(psy)->extensions, list_head)	\
>
>   #ifdef CONFIG_SYSFS
>
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index 502b07468b93dfb7f5a6c2092588d931a7d015f2..bc22edbd0e6a02c27500132075f5c98d814a7330 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -81,6 +81,7 @@ static int __power_supply_changed_work(struct device *dev, void *data)
>
>   static void power_supply_changed_work(struct work_struct *work)
>   {
> +	int ret;
>   	unsigned long flags;
>   	struct power_supply *psy = container_of(work, struct power_supply,
>   						changed_work);
> @@ -88,6 +89,16 @@ static void power_supply_changed_work(struct work_struct *work)
>   	dev_dbg(&psy->dev, "%s\n", __func__);
>
>   	spin_lock_irqsave(&psy->changed_lock, flags);
> +
> +	if (unlikely(psy->update_groups)) {
> +		psy->update_groups = false;
> +		spin_unlock_irqrestore(&psy->changed_lock, flags);
> +		ret = sysfs_update_groups(&psy->dev.kobj, power_supply_dev_type.groups);
> +		if (ret)
> +			dev_warn(&psy->dev, "failed to update sysfs groups: %pe\n", ERR_PTR(ret));
> +		spin_lock_irqsave(&psy->changed_lock, flags);
> +	}
> +
>   	/*
>   	 * Check 'changed' here to avoid issues due to race between
>   	 * power_supply_changed() and this routine. In worst case
> @@ -1196,15 +1207,34 @@ static bool psy_desc_has_property(const struct power_supply_desc *psy_desc,
>   	return found;
>   }
>
> +bool power_supply_ext_has_property(const struct power_supply_ext *psy_ext,
> +				   enum power_supply_property psp)
> +{
> +	int i;
> +
> +	for (i = 0; i < psy_ext->num_properties; i++)
> +		if (psy_ext->properties[i] == psp)
> +			return true;
> +
> +	return false;
> +}
> +
>   bool power_supply_has_property(struct power_supply *psy,
>   			       enum power_supply_property psp)
>   {
> +	struct power_supply_ext_registration *reg;
> +
>   	if (psy_desc_has_property(psy->desc, psp))
>   		return true;
>
>   	if (power_supply_battery_info_has_prop(psy->battery_info, psp))
>   		return true;
>
> +	power_supply_for_each_extension(reg, psy) {
> +		if (power_supply_ext_has_property(reg->ext, psp))
> +			return true;
> +	}
> +
>   	return false;
>   }
>
> @@ -1212,12 +1242,21 @@ int power_supply_get_property(struct power_supply *psy,
>   			    enum power_supply_property psp,
>   			    union power_supply_propval *val)
>   {
> +	struct power_supply_ext_registration *reg;
> +
>   	if (atomic_read(&psy->use_cnt) <= 0) {
>   		if (!psy->initialized)
>   			return -EAGAIN;
>   		return -ENODEV;
>   	}
>
> +	scoped_guard(rwsem_read, &psy->extensions_sem) {
> +		power_supply_for_each_extension(reg, psy) {
> +			if (power_supply_ext_has_property(reg->ext, psp))
> +				return reg->ext->get_property(psy, reg->ext, reg->data, psp, val);
> +		}
> +	}
> +
>   	if (psy_desc_has_property(psy->desc, psp))
>   		return psy->desc->get_property(psy, psp, val);
>   	else if (power_supply_battery_info_has_prop(psy->battery_info, psp))
> @@ -1231,7 +1270,24 @@ int power_supply_set_property(struct power_supply *psy,
>   			    enum power_supply_property psp,
>   			    const union power_supply_propval *val)
>   {
> -	if (atomic_read(&psy->use_cnt) <= 0 || !psy->desc->set_property)
> +	struct power_supply_ext_registration *reg;
> +
> +	if (atomic_read(&psy->use_cnt) <= 0)
> +		return -ENODEV;
> +
> +	scoped_guard(rwsem_read, &psy->extensions_sem) {
> +		power_supply_for_each_extension(reg, psy) {
> +			if (power_supply_ext_has_property(reg->ext, psp)) {
> +				if (reg->ext->set_property)
> +					return reg->ext->set_property(psy, reg->ext, reg->data,
> +								      psp, val);
> +				else
> +					return -ENODEV;
> +			}
> +		}
> +	}
> +
> +	if (!psy->desc->set_property)
>   		return -ENODEV;
>
>   	return psy->desc->set_property(psy, psp, val);
> @@ -1241,7 +1297,22 @@ EXPORT_SYMBOL_GPL(power_supply_set_property);
>   int power_supply_property_is_writeable(struct power_supply *psy,
>   					enum power_supply_property psp)
>   {
> -	return psy->desc->property_is_writeable && psy->desc->property_is_writeable(psy, psp);
> +	struct power_supply_ext_registration *reg;
> +
> +	power_supply_for_each_extension(reg, psy) {
> +		if (power_supply_ext_has_property(reg->ext, psp)) {
> +			if (reg->ext->property_is_writeable)
> +				return reg->ext->property_is_writeable(psy, reg->ext,
> +								       reg->data, psp);
> +			else
> +				return 0;
> +		}
> +	}
> +
> +	if (!psy->desc->property_is_writeable)
> +		return 0;
> +
> +	return psy->desc->property_is_writeable(psy, psp);
>   }
>
>   void power_supply_external_power_changed(struct power_supply *psy)
> @@ -1260,6 +1331,76 @@ int power_supply_powers(struct power_supply *psy, struct device *dev)
>   }
>   EXPORT_SYMBOL_GPL(power_supply_powers);
>
> +static int power_supply_update_sysfs_and_hwmon(struct power_supply *psy)
> +{
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&psy->changed_lock, flags);
> +	psy->update_groups = true;
> +	spin_unlock_irqrestore(&psy->changed_lock, flags);
> +
> +	power_supply_changed(psy);
> +
> +	power_supply_remove_hwmon_sysfs(psy);
> +	return power_supply_add_hwmon_sysfs(psy);
> +}
> +
> +int power_supply_register_extension(struct power_supply *psy, const struct power_supply_ext *ext,
> +				    void *data)
> +{
> +	struct power_supply_ext_registration *reg;
> +	size_t i;
> +	int ret;
> +
> +	if (!psy || !ext || !ext->properties || !ext->num_properties)
> +		return -EINVAL;
> +
> +	guard(rwsem_write)(&psy->extensions_sem);
> +
> +	for (i = 0; i < ext->num_properties; i++)
> +		if (power_supply_has_property(psy, ext->properties[i]))
> +			return -EEXIST;
> +
> +	reg = kmalloc(sizeof(*reg), GFP_KERNEL);
> +	if (!reg)
> +		return -ENOMEM;
> +
> +	reg->ext = ext;
> +	reg->data = data;
> +	list_add(&reg->list_head, &psy->extensions);
> +
> +	ret = power_supply_update_sysfs_and_hwmon(psy);
> +	if (ret)
> +		goto sysfs_hwmon_failed;
> +
> +	return 0;
> +
> +sysfs_hwmon_failed:
> +	list_del(&reg->list_head);
> +	kfree(reg);
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(power_supply_register_extension);
> +
> +void power_supply_unregister_extension(struct power_supply *psy, const struct power_supply_ext *ext)
> +{
> +	struct power_supply_ext_registration *reg;
> +
> +	guard(rwsem_write)(&psy->extensions_sem);
> +
> +	power_supply_for_each_extension(reg, psy) {
> +		if (reg->ext == ext) {
> +			list_del(&reg->list_head);
> +			kfree(reg);
> +			power_supply_update_sysfs_and_hwmon(psy);
> +			return;
> +		}
> +	}
> +
> +	dev_warn(&psy->dev, "Trying to unregister invalid extension");
> +}
> +EXPORT_SYMBOL_GPL(power_supply_unregister_extension);
> +
>   static void power_supply_dev_release(struct device *dev)
>   {
>   	struct power_supply *psy = to_power_supply(dev);
> @@ -1414,6 +1555,9 @@ __power_supply_register(struct device *parent,
>   	}
>
>   	spin_lock_init(&psy->changed_lock);
> +	init_rwsem(&psy->extensions_sem);
> +	INIT_LIST_HEAD(&psy->extensions);
> +
>   	rc = device_add(dev);
>   	if (rc)
>   		goto device_add_failed;
> @@ -1426,13 +1570,15 @@ __power_supply_register(struct device *parent,
>   	if (rc)
>   		goto register_thermal_failed;
>
> -	rc = power_supply_create_triggers(psy);
> -	if (rc)
> -		goto create_triggers_failed;
> +	scoped_guard(rwsem_read, &psy->extensions_sem) {
> +		rc = power_supply_create_triggers(psy);
> +		if (rc)
> +			goto create_triggers_failed;
>
> -	rc = power_supply_add_hwmon_sysfs(psy);
> -	if (rc)
> -		goto add_hwmon_sysfs_failed;
> +		rc = power_supply_add_hwmon_sysfs(psy);
> +		if (rc)
> +			goto add_hwmon_sysfs_failed;
> +	}
>
>   	/*
>   	 * Update use_cnt after any uevents (most notably from device_add()).
> diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
> index 99bfe1f03eb8326d38c4e2831c9670313b42e425..927ddb9d83bb7259809ba695cb9398d1ad654b46 100644
> --- a/drivers/power/supply/power_supply_sysfs.c
> +++ b/drivers/power/supply/power_supply_sysfs.c
> @@ -268,6 +268,27 @@ static ssize_t power_supply_show_enum_with_available(
>   	return count;
>   }
>
> +static ssize_t power_supply_show_charge_behaviour(struct device *dev,
> +						  struct power_supply *psy,
> +						  union power_supply_propval *value,
> +						  char *buf)
> +{
> +	struct power_supply_ext_registration *reg;
> +
> +	scoped_guard(rwsem_read, &psy->extensions_sem) {
> +		power_supply_for_each_extension(reg, psy) {
> +			if (power_supply_ext_has_property(reg->ext,
> +							  POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR))
> +				return power_supply_charge_behaviour_show(dev,
> +						reg->ext->charge_behaviours,
> +						value->intval, buf);
> +		}
> +	}
> +
> +	return power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
> +						  value->intval, buf);
> +}
> +
>   static ssize_t power_supply_format_property(struct device *dev,
>   					    bool uevent,
>   					    struct device_attribute *attr,
> @@ -307,8 +328,7 @@ static ssize_t power_supply_format_property(struct device *dev,
>   	case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
>   		if (uevent) /* no possible values in uevents */
>   			goto default_format;
> -		ret = power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
> -							 value.intval, buf);
> +		ret = power_supply_show_charge_behaviour(dev, psy, &value, buf);
>   		break;
>   	case POWER_SUPPLY_PROP_MODEL_NAME ... POWER_SUPPLY_PROP_SERIAL_NUMBER:
>   		ret = sysfs_emit(buf, "%s\n", value.strval);
> @@ -385,6 +405,8 @@ static umode_t power_supply_attr_is_visible(struct kobject *kobj,
>   	if (attrno == POWER_SUPPLY_PROP_TYPE)
>   		return mode;
>
> +	guard(rwsem_read)(&psy->extensions_sem);
> +
>   	if (power_supply_has_property(psy, attrno)) {
>   		if (power_supply_property_is_writeable(psy, attrno) > 0)
>   			mode |= S_IWUSR;
> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
> index b98106e1a90f34bce5129317a099f363248342b9..e434516086f032cdb4698005bb1a99eda303a307 100644
> --- a/include/linux/power_supply.h
> +++ b/include/linux/power_supply.h
> @@ -15,6 +15,8 @@
>   #include <linux/device.h>
>   #include <linux/workqueue.h>
>   #include <linux/leds.h>
> +#include <linux/rwsem.h>
> +#include <linux/list.h>
>   #include <linux/spinlock.h>
>   #include <linux/notifier.h>
>
> @@ -281,6 +283,27 @@ struct power_supply_desc {
>   	int use_for_apm;
>   };
>
> +struct power_supply_ext {
> +	u8 charge_behaviours;
> +	const enum power_supply_property *properties;
> +	size_t num_properties;
> +
> +	int (*get_property)(struct power_supply *psy,
> +			    const struct power_supply_ext *ext,
> +			    void *data,
> +			    enum power_supply_property psp,
> +			    union power_supply_propval *val);
> +	int (*set_property)(struct power_supply *psy,
> +			    const struct power_supply_ext *ext,
> +			    void *data,
> +			    enum power_supply_property psp,
> +			    const union power_supply_propval *val);
> +	int (*property_is_writeable)(struct power_supply *psy,
> +				     const struct power_supply_ext *ext,
> +				     void *data,
> +				     enum power_supply_property psp);
> +};
> +
>   struct power_supply {
>   	const struct power_supply_desc *desc;
>
> @@ -300,10 +323,13 @@ struct power_supply {
>   	struct delayed_work deferred_register_work;
>   	spinlock_t changed_lock;
>   	bool changed;
> +	bool update_groups;
>   	bool initialized;
>   	bool removing;
>   	atomic_t use_cnt;
>   	struct power_supply_battery_info *battery_info;
> +	struct rw_semaphore extensions_sem; /* protects "extensions" */
> +	struct list_head extensions;
>   #ifdef CONFIG_THERMAL
>   	struct thermal_zone_device *tzd;
>   	struct thermal_cooling_device *tcd;
> @@ -878,6 +904,13 @@ devm_power_supply_register(struct device *parent,
>   extern void power_supply_unregister(struct power_supply *psy);
>   extern int power_supply_powers(struct power_supply *psy, struct device *dev);
>
> +extern int __must_check
> +power_supply_register_extension(struct power_supply *psy,
> +				const struct power_supply_ext *ext,
> +				void *data);
> +extern void power_supply_unregister_extension(struct power_supply *psy,
> +					      const struct power_supply_ext *ext);
> +
>   #define to_power_supply(device) container_of(device, struct power_supply, dev)
>
>   extern void *power_supply_get_drvdata(struct power_supply *psy);
>