Power supply

Power supply (<tt>rt_power_supply</tt>)

Header: **components/drivers/include/drivers/power_supply.h**. Core: **components/drivers/power/supply/supply.c**.

Models batteries, USB ports, mains, etc. as property objects (Linux power_supply–like). Chargers use the same class — Charger (gpio-charger).

Kconfig: **RT_USING_POWER_SUPPLY**, optional **RT_POWER_SUPPLY_DAEMON**.

---

Architecture

Platform driver probe
        |
        v
  Fill struct rt_power_supply (type, properties, ops, dev)
        |
        v
  rt_power_supply_register(psy)
        |
        +-- global list + rt_ofw_data(np) = psy
        +-- optional thermal zone (PROP_TEMP)
        +-- changed_work for notifiers / LED update
        |
        v
  Consumers: rt_power_supply_get_property / notifier / daemon

There is no separate platform bus for power supplies: the platform driver owns **struct rt_platform_device**, and the **rt_power_supply** hangs off **psy->dev = &pdev->parent**.

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Registering a power supply (important)

1. Platform driver (<tt>RT_PLATFORM_DRIVER_EXPORT</tt>)

Bind to DT with **compatible**, then register the supply in **probe**:

struct my_psy_priv {
    struct rt_power_supply psy;
    /* hardware state */
};
 
static enum rt_power_supply_property my_props[] = {
    RT_POWER_SUPPLY_PROP_STATUS,
    RT_POWER_SUPPLY_PROP_CAPACITY,
};
 
static rt_err_t my_get_property(struct rt_power_supply *psy,
        enum rt_power_supply_property prop, union rt_power_supply_property_val *val)
{
    /* read hardware, fill val->intval or val->strval */
    return RT_EOK;
}
 
static const struct rt_power_supply_ops my_ops = {
    .get_property = my_get_property,
};
 
static rt_err_t my_probe(struct rt_platform_device *pdev)
{
    struct rt_device *dev = &pdev->parent;
    struct my_psy_priv *priv = rt_calloc(1, sizeof(*priv));
 
    priv->psy.dev = dev;
    priv->psy.type = RT_POWER_SUPPLY_TYPE_BATTERY;
    priv->psy.properties = my_props;
    priv->psy.properties_nr = RT_ARRAY_SIZE(my_props);
    priv->psy.ops = &my_ops;
 
    return rt_power_supply_register(&priv->psy);
}
 
static rt_err_t my_remove(struct rt_platform_device *pdev)
{
    struct my_psy_priv *priv = rt_dm_dev_get_fwdata(&pdev->parent);
    rt_power_supply_unregister(&priv->psy);
    rt_free(priv);
    return RT_EOK;
}

Reference: **gpio-charger.c** — **RT_PLATFORM_DRIVER_EXPORT(gpio_charger_driver)**.

2. <tt>rt_power_supply_register</tt> requirements

Field	Required
**psy->dev**	Yes — usually **&pdev->parent**
**psy->ops** + **properties** + **properties_nr**	Yes, unless **battery_info** is set (static battery descriptor path)
**psy->type**	Set before register (USB type, battery, mains, …)
**psy->battery_info**	Alternative to dynamic properties for some battery profiles

On success:

• Inserts **psy** into global list
• **rt_dm_dev_bind_fwdata(psy->dev, NULL, psy)** when **dev->ofw_node** is set
• Initializes **changed_work** for **rt_power_supply_changed()**

**rt_power_supply_unregister**: removes from list; fails with **-RT_EBUSY** if **rt_power_supply_get** refcount > 1.

3. Optional: <tt>set_property</tt>

Implement **ops->set_property** for writable limits (e.g. charge current). Only properties listed in **properties[]** are exposed via **rt_power_supply_set_property**.

4. Notify userspace / daemon / LED

After hardware state changes (GPIO IRQ, PMIC interrupt):

rt_power_supply_changed(psy);

This queues **power_supply_changed_work**, which:

• Updates bound **led_dev** if **RT_USING_LED**
• Calls all **rt_power_supply_notifier** callbacks

Register a notifier:

static rt_err_t my_notify(struct rt_power_supply_notifier *n,
        struct rt_power_supply *psy) { ... return RT_EOK; }
 
static struct rt_power_supply_notifier n = {
    .callback = my_notify,
};
rt_power_supply_notifier_register(&n);

**RT_POWER_SUPPLY_DAEMON**: built-in notifier drives low-battery / PM hints when **RT_USING_PM**.

---

Property API

rt_err_t rt_power_supply_get_property(psy, prop, &val);
rt_err_t rt_power_supply_set_property(psy, prop, &val);

**get_property** only succeeds if **prop** is in **psy->properties[]** (or **battery_info** path for supported static props).

Common properties: **STATUS**, **CAPACITY**, **ONLINE**, **VOLTAGE_NOW**, **CURRENT_NOW**, **TEMP**, **CONSTANT_CHARGE_CURRENT_MAX**, … — see enum in **power_supply.h**.

---

Lookup from another device

struct rt_power_supply *psy = rt_power_supply_get(consumer_dev, "battery");
if (rt_is_err(psy))
    ...
rt_power_supply_get_property(psy, RT_POWER_SUPPLY_PROP_CAPACITY, &val);
rt_power_supply_put(psy);

**id** is a DT phandle property name on **consumer_dev** (e.g. **power-supply = <&bat>** → **"power-supply"**). Resolves **rt_ofw_data** on the supply’s OFW node after register.

---

DT consumer example

thermal-zone {
    polling-delay = <1000>;
    thermal-sensors = <&bat>;
};
 
bat: battery {
    compatible = "vendor,fuel-gauge";
    monitored-battery;
};

Fuel-gauge driver **probe** registers **rt_power_supply** on node **bat**. Thermal references **&bat** via **rt_power_supply_thermal_register** when **PROP_TEMP** exists.

---

Integration

Subsystem	Hook
LED	Assign **psy->led_dev** before register; **changed** updates indicators
Thermal	**power_supply_thermal_register** if **PROP_TEMP**
Regulator	Charger **set_property** may adjust rails (see **gpio-charger**)
PM	Daemon may request sleep modes on low SOC

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Pitfalls

Issue	Mitigation
Register before **psy->dev** set	**register** returns **-RT_EINVAL**
Empty **properties**	Must list every prop **get_property** handles
Forget **rt_power_supply_changed**	Notifiers/LED/PM stay stale
**unregister with active get**	**put** all references first
**get_property from ISR**	Defer to workqueue; gauge I2C may block
Stale SOC cache	Re-read hardware in **get_property**

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See also

• Power subsystem overview — stack overview
• Charger (gpio-charger) — **gpio-charger**
• Platform bus — driver export
• components/drivers/power/supply/supply.c