Re: [PATCH v2 1/2] power: supply: Add helpers to get and put arrays of power supply handles

[Hans de Goede <hansg@kernel.org>]

Hi,

Thank you for the new version.

On 27-May-26 02:02, Amit Sunil Dhamne via B4 Relay wrote:
> From: Amit Sunil Dhamne <amitsd@google.com>
> 
> Add power_supply_get_battery_all() to allow drivers to obtain a list of
> registered battery type power supply references in the system. Also add
> power_supply_put_array() to release references to the power supplies
> when no longer needed.
> 
> Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
> ---
>  drivers/power/supply/power_supply_core.c | 137 +++++++++++++++++++++++++++++++
>  include/linux/power_supply.h             |  12 +++
>  2 files changed, 149 insertions(+)
> 
> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
> index a446d3d086fc..04e5c1083e8f 100644
> --- a/drivers/power/supply/power_supply_core.c
> +++ b/drivers/power/supply/power_supply_core.c
> @@ -482,6 +482,127 @@ struct power_supply *power_supply_get_by_name(const char *name)
>  }
>  EXPORT_SYMBOL_GPL(power_supply_get_by_name);
>  
> +static int __power_supply_get_num_battery(struct power_supply *epsy, void *data)
> +{
> +	int *count = data;
> +
> +	if (epsy->desc->type == POWER_SUPPLY_TYPE_BATTERY)
> +		(*count)++;
> +
> +	return 0;
> +}
> +
> +static int power_supply_get_num_battery(struct device *dev)
> +{
> +	int ret, count = 0;
> +
> +	ret = power_supply_for_each_psy(&count, __power_supply_get_num_battery);
> +
> +	dev_dbg(dev, "%s: count: %d ret %d\n", __func__, count, ret);
> +
> +	if (ret)
> +		return ret;
> +
> +	return count;
> +}
> +
> +struct psy_get_supplies_data {
> +	int cnt;
> +	int size;
> +	struct power_supply **psys;
> +};
> +
> +static int __power_supply_populate_battery_array(struct power_supply *epsy,
> +						 void *_data)
> +{
> +	struct psy_get_supplies_data *data = _data;
> +
> +	if (epsy->desc->type == POWER_SUPPLY_TYPE_BATTERY) {
> +		if (data->size <= data->cnt)
> +			return -EOVERFLOW;
> +
> +		get_device(&epsy->dev);
> +		data->psys[data->cnt] = epsy;
> +		atomic_inc(&epsy->use_cnt);
> +		data->cnt++;
> +	}
> +
> +	return 0;
> +}
> +
> +static int power_supply_populate_battery_array(struct device *dev, int size,
> +					       struct power_supply **batteries)
> +{
> +	int ret;
> +
> +	struct psy_get_supplies_data data = {
> +		.cnt = 0,
> +		.size = size,
> +		.psys = batteries,
> +	};
> +
> +	ret = power_supply_for_each_psy(&data, __power_supply_populate_battery_array);
> +
> +	dev_dbg(dev, "%s Found %d batteries with array size %d ret %d\n",
> +		__func__, data.cnt, data.size, ret);
> +
> +	if (ret < 0) {
> +		power_supply_put_array(batteries, data.cnt);
> +		return ret;
> +	}
> +
> +	return data.cnt;
> +}
> +
> +/**
> + * power_supply_get_battery_all() - Fetches references to all battery type power
> + *                                  supplies.
> + * @dev: Pointer to device requesting the power supply refs.
> + * @psys: Pointer to an array of power supply refs.
> + *
> + * Helper function to get handles to all battery type power supplies.
> + * If acquiring a ref to a power supply fails, then the search for battery
> + * type power supplies will abort and the acquired power supply references will
> + * be released.
> + *
> + * Return: Indicates the number of battery type power supplies returned on
> + * success or a negative error code on failure.
> + *
> + * The caller should invoke power_supply_put_array() on the returned array
> + * of psy refs and free the array returned by this function using kfree()
> + * after use.
> + */
> +int __must_check power_supply_get_battery_all(struct device *dev,
> +					      struct power_supply ***psys)
> +{
> +	int ret;
> +
> +	if (!psys)
> +		return -EINVAL;
> +
> +	ret = power_supply_get_num_battery(dev);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (!ret) {
> +		*psys = NULL;
> +		return 0;
> +	}
> +
> +	*psys = kzalloc_objs(**psys, ret);
> +	if (!*psys)
> +		return -ENOMEM;
> +
> +	ret = power_supply_populate_battery_array(dev, ret, *psys);
> +	if (ret <= 0) {
> +		kfree(*psys);
> +		*psys = NULL;
> +	}
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(power_supply_get_battery_all);
> +
>  /**
>   * power_supply_put() - Drop reference obtained with power_supply_get_by_name
>   * @psy: Reference to put
> @@ -496,6 +617,22 @@ void power_supply_put(struct power_supply *psy)
>  }
>  EXPORT_SYMBOL_GPL(power_supply_put);
>  
> +/**
> + * power_supply_put_array() - Drop references to an array of power supplies.
> + * @psys: Array of power supply references to put.
> + * @count: Number of elements in the array.
> + */
> +void power_supply_put_array(struct power_supply **psys, int count)
> +{
> +	int i;
> +
> +	for (i = 0; i < count; i++) {
> +		if (psys[i])
> +			power_supply_put(psys[i]);
> +	}
> +}
> +EXPORT_SYMBOL_GPL(power_supply_put_array);
> +

I think it would be better to call this: power_supply_put_battery_all()
and move it to directly below power_supply_get_battery_all()and also
have it call kfree(psys) so that it does all the teardown of what
power_supply_get_battery_all() has done.

Regards,

Hans



>  static int power_supply_match_device_fwnode(struct device *dev, const void *data)
>  {
>  	return dev->parent && dev_fwnode(dev->parent) == data;
> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
> index 7a5e4c3242a0..026412164a88 100644
> --- a/include/linux/power_supply.h
> +++ b/include/linux/power_supply.h
> @@ -806,11 +806,23 @@ extern int power_supply_reg_notifier(struct notifier_block *nb);
>  extern void power_supply_unreg_notifier(struct notifier_block *nb);
>  #if IS_ENABLED(CONFIG_POWER_SUPPLY)
>  extern struct power_supply *power_supply_get_by_name(const char *name);
> +extern int __must_check power_supply_get_battery_all(struct device *dev,
> +						     struct power_supply ***psys);
> +extern void power_supply_put_array(struct power_supply **psys, int count);
>  extern void power_supply_put(struct power_supply *psy);
>  #else
>  static inline void power_supply_put(struct power_supply *psy) {}
>  static inline struct power_supply *power_supply_get_by_name(const char *name)
>  { return NULL; }
> +static inline int __must_check power_supply_get_battery_all(struct device *dev,
> +							    struct power_supply ***psys)
> +{
> +	if (psys)
> +		*psys = NULL;
> +	return 0;
> +}
> +
> +static inline void power_supply_put_array(struct power_supply **psys, int count) {}
>  #endif
>  extern struct power_supply *power_supply_get_by_reference(struct fwnode_handle *fwnode,
>  							  const char *property);
>