Re: [PATCH 2/5] power: supply: core: add function to get supplies from fwnode

[Amit Sunil Dhamne <amitsd@google.com>]

On 3/19/25 6:54 AM, Heikki Krogerus wrote:
> On Wed, Mar 12, 2025 at 04:42:02PM -0700, Amit Sunil Dhamne via B4 Relay wrote:
>> From: Amit Sunil Dhamne <amitsd@google.com>
>>
>> Add a new helper function power_supply_get_by_fwnode_reference_array()
>> to retrieve a list of power_supplies associated with the fwnode's
>> property. The property can contain multiple nodes where each node is
>> associated with a power_supply. The list of power_supply objects will be
>> stored in an array supplied by the caller and the return value will
>> indicate the size of the resulting array.
> I don't think this API is necessary. If I've understood what you are
> after here, the batteries should simply have the Type-C psy(s) listed
> in the supplied_to and/or supplied_from.
>
> So you just need to make sure your battery nodes have the USB Type-C
> node(s) listed in the "power-supplies" property in your DT, no?
Thanks Heikki! I will evaluate between this approach vs OF graph 
approach (as suggested in previous review) and implement it in v2.
>
> thanks,
>> Signed-off-by: Amit Sunil Dhamne <amitsd@google.com>
>> ---
>>   drivers/power/supply/power_supply_core.c | 60 ++++++++++++++++++++++++++++++++
>>   include/linux/power_supply.h             |  5 +++
>>   2 files changed, 65 insertions(+)
>>
>> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
>> index 76c340b38015af0a67a0d91305e6242a8646bf53..df1a52f85125748c4fdcb10687aa7ed2f626ded1 100644
>> --- a/drivers/power/supply/power_supply_core.c
>> +++ b/drivers/power/supply/power_supply_core.c
>> @@ -593,6 +593,66 @@ struct power_supply *devm_power_supply_get_by_phandle(struct device *dev,
>>   EXPORT_SYMBOL_GPL(devm_power_supply_get_by_phandle);
>>   #endif /* CONFIG_OF */
>>   
>> +static int power_supply_match_fwnode(struct device *dev, const void *data)
>> +{
>> +	return dev && dev->parent && dev->parent->fwnode == data;
>> +}
>> +
>> +/**
>> + * power_supply_get_by_fwnode_reference_array() - Returns an array of power
>> + * supply objects associated with each fwnode reference present in the property
>> + * @fwnode: Pointer to fwnode to lookup property
>> + * @property: Name of property holding references
>> + * @psy: Resulting array of power_supply pointers. To be provided by the caller.
>> + * @size: size of power_supply pointer array.
>> + *
>> + * If power supply was found, it increases reference count for the
>> + * internal power supply's device. The user should power_supply_put()
>> + * after usage.
>> + *
>> + * Return: On success returns the number of power supply objects filled
>> + * in the @psy array.
>> + * -EOVERFLOW when size of @psy array is not suffice.
>> + * -EINVAL when @psy is NULL or @size is 0.
>> + * -ENODATA when fwnode does not contain the given property
>> + */
>> +int power_supply_get_by_fwnode_reference_array(struct fwnode_handle *fwnode,
>> +					       const char *property,
>> +					       struct power_supply **psy,
>> +					       ssize_t size)
>> +{
>> +	int ret, index, count = 0;
>> +	struct fwnode_reference_args args;
>> +	struct device *dev;
>> +
>> +	if (!psy || !size)
>> +		return -EINVAL;
>> +
>> +	for (index = 0; index < size &&
>> +	     !(ret = fwnode_property_get_reference_args(fwnode, property, NULL,
>> +							0, index, &args));
>> +	     ++index) {
>> +		dev = class_find_device(&power_supply_class, NULL, args.fwnode,
>> +					power_supply_match_fwnode);
>> +		fwnode_handle_put(args.fwnode);
>> +		if (!dev)
>> +			continue;
>> +
>> +		if (count > size)
>> +			return -EOVERFLOW;
>> +
>> +		psy[count] = dev_get_drvdata(dev);
>> +		atomic_inc(&psy[count]->use_cnt);
>> +		++count;
>> +	}
>> +
>> +	if (ret != -ENOENT)
>> +		return ret;
>> +
>> +	return index ? count : -ENODATA;
>> +}
>> +EXPORT_SYMBOL_GPL(power_supply_get_by_fwnode_reference_array);
>> +
>>   int power_supply_get_battery_info(struct power_supply *psy,
>>   				  struct power_supply_battery_info **info_out)
>>   {
>> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
>> index 6ed53b292162469d7b357734d5589bff18a201d0..3f062607e5cd7c7f04384e34128ae0953e25d981 100644
>> --- a/include/linux/power_supply.h
>> +++ b/include/linux/power_supply.h
>> @@ -820,6 +820,11 @@ devm_power_supply_get_by_phandle(struct device *dev, const char *property)
>>   { return NULL; }
>>   #endif /* CONFIG_OF */
>>   
>> +extern int
>> +power_supply_get_by_fwnode_reference_array(struct fwnode_handle *fwnode,
>> +					   const char *property,
>> +					   struct power_supply **psy,
>> +					   ssize_t size);
>>   extern const enum power_supply_property power_supply_battery_info_properties[];
>>   extern const size_t power_supply_battery_info_properties_size;
>>   extern int power_supply_get_battery_info(struct power_supply *psy,
>>
>> -- 
>> 2.49.0.rc0.332.g42c0ae87b1-goog
>>