Re: [PATCH 1/3] power: supply: core: Add power_supply_get/set_property_direct()

[Armin Wolf <W_Armin@gmx.de>]

Am 28.06.25 um 11:25 schrieb Hans de Goede:

> Hi Armin,
>
> On 27-Jun-25 10:51 PM, Armin Wolf wrote:
>> Power supply extensions might want to interact with the underlying
>> power supply to retrieve data like serial numbers, charging status
>> and more. However doing so causes psy->extensions_sem to be locked
>> twice, possibly causing a deadlock.
>>
>> Provide special variants of power_supply_get/set_property() that
>> ignore any power supply extensions and thus do not touch the
>> associated psy->extensions_sem lock.
>>
>> Suggested-by: Hans de Goede <hansg@kernel.org>
>> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
> Thank you for your work on this.
>
> The entire series looks good to me:
>
> Reviewed-by: Hans de Goede <hansg@kernel.org>
>
> for the series.
>
> There is the question of how to merge this. I think it might
> be best for the entire series to go through the power-supply
> tree.
>
> Ilpo would that work for you and if yes can we have your ack ?
>
> Sebastian, IMHO this should be merged as fixed not as for-next
> material.
>
> Regards,
>
> Hans

Personally i would prefer to merge this through the pdx86 tree as the
uniwill-laptop driver currently under review will also require this functionality.

Thanks,
Armin Wolf

>> ---
>>   drivers/power/supply/power_supply_core.c | 82 ++++++++++++++++++++----
>>   include/linux/power_supply.h             |  8 +++
>>   2 files changed, 78 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
>> index aedb20c1d276..e70ffedf1a80 100644
>> --- a/drivers/power/supply/power_supply_core.c
>> +++ b/drivers/power/supply/power_supply_core.c
>> @@ -1241,9 +1241,8 @@ bool power_supply_has_property(struct power_supply *psy,
>>   	return false;
>>   }
>>   
>> -int power_supply_get_property(struct power_supply *psy,
>> -			    enum power_supply_property psp,
>> -			    union power_supply_propval *val)
>> +static int __power_supply_get_property(struct power_supply *psy, enum power_supply_property psp,
>> +				       union power_supply_propval *val, bool use_extensions)
>>   {
>>   	struct power_supply_ext_registration *reg;
>>   
>> @@ -1253,10 +1252,14 @@ int power_supply_get_property(struct power_supply *psy,
>>   		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 (use_extensions) {
>> +		scoped_guard(rwsem_read, &psy->extensions_sem) {
>> +			power_supply_for_each_extension(reg, psy) {
>> +				if (!power_supply_ext_has_property(reg->ext, psp))
>> +					continue;
>> +
>>   				return reg->ext->get_property(psy, reg->ext, reg->data, psp, val);
>> +			}
>>   		}
>>   	}
>>   
>> @@ -1267,20 +1270,49 @@ int power_supply_get_property(struct power_supply *psy,
>>   	else
>>   		return -EINVAL;
>>   }
>> +
>> +int power_supply_get_property(struct power_supply *psy, enum power_supply_property psp,
>> +			      union power_supply_propval *val)
>> +{
>> +	return __power_supply_get_property(psy, psp, val, true);
>> +}
>>   EXPORT_SYMBOL_GPL(power_supply_get_property);
>>   
>> -int power_supply_set_property(struct power_supply *psy,
>> -			    enum power_supply_property psp,
>> -			    const union power_supply_propval *val)
>> +/**
>> + * power_supply_get_property_direct - Read a power supply property without checking for extensions
>> + * @psy: The power supply
>> + * @psp: The power supply property to read
>> + * @val: The resulting value of the power supply property
>> + *
>> + * Read a power supply property without taking into account any power supply extensions registered
>> + * on the given power supply. This is mostly useful for power supply extensions that want to access
>> + * their own power supply as using power_supply_get_property() directly will result in a potential
>> + * deadlock.
>> + *
>> + * Return: 0 on success or negative error code on failure.
>> + */
>> +int power_supply_get_property_direct(struct power_supply *psy, enum power_supply_property psp,
>> +				     union power_supply_propval *val)
>> +{
>> +        return __power_supply_get_property(psy, psp, val, false);
>> +}
>> +EXPORT_SYMBOL_GPL(power_supply_get_property_direct);
>> +
>> +
>> +static int __power_supply_set_property(struct power_supply *psy, enum power_supply_property psp,
>> +				       const union power_supply_propval *val, bool use_extensions)
>>   {
>>   	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 (use_extensions) {
>> +		scoped_guard(rwsem_read, &psy->extensions_sem) {
>> +			power_supply_for_each_extension(reg, psy) {
>> +				if (!power_supply_ext_has_property(reg->ext, psp))
>> +					continue;
>> +
>>   				if (reg->ext->set_property)
>>   					return reg->ext->set_property(psy, reg->ext, reg->data,
>>   								      psp, val);
>> @@ -1295,8 +1327,34 @@ int power_supply_set_property(struct power_supply *psy,
>>   
>>   	return psy->desc->set_property(psy, psp, val);
>>   }
>> +
>> +int power_supply_set_property(struct power_supply *psy, enum power_supply_property psp,
>> +			      const union power_supply_propval *val)
>> +{
>> +	return __power_supply_set_property(psy, psp, val, true);
>> +}
>>   EXPORT_SYMBOL_GPL(power_supply_set_property);
>>   
>> +/**
>> + * power_supply_set_property_direct - Write a power supply property without checking for extensions
>> + * @psy: The power supply
>> + * @psp: The power supply property to write
>> + * @val: The value to write to the power supply property
>> + *
>> + * Write a power supply property without taking into account any power supply extensions registered
>> + * on the given power supply. This is mostly useful for power supply extensions that want to access
>> + * their own power supply as using power_supply_set_property() directly will result in a potential
>> + * deadlock.
>> + *
>> + * Return: 0 on success or negative error code on failure.
>> + */
>> +int power_supply_set_property_direct(struct power_supply *psy, enum power_supply_property psp,
>> +				     const union power_supply_propval *val)
>> +{
>> +	return __power_supply_set_property(psy, psp, val, false);
>> +}
>> +EXPORT_SYMBOL_GPL(power_supply_set_property_direct);
>> +
>>   int power_supply_property_is_writeable(struct power_supply *psy,
>>   					enum power_supply_property psp)
>>   {
>> diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
>> index 45468959dd98..f21f806bfb38 100644
>> --- a/include/linux/power_supply.h
>> +++ b/include/linux/power_supply.h
>> @@ -878,15 +878,23 @@ static inline int power_supply_is_system_supplied(void) { return -ENOSYS; }
>>   extern int power_supply_get_property(struct power_supply *psy,
>>   			    enum power_supply_property psp,
>>   			    union power_supply_propval *val);
>> +int power_supply_get_property_direct(struct power_supply *psy, enum power_supply_property psp,
>> +				     union power_supply_propval *val);
>>   #if IS_ENABLED(CONFIG_POWER_SUPPLY)
>>   extern int power_supply_set_property(struct power_supply *psy,
>>   			    enum power_supply_property psp,
>>   			    const union power_supply_propval *val);
>> +int power_supply_set_property_direct(struct power_supply *psy, enum power_supply_property psp,
>> +				     const union power_supply_propval *val);
>>   #else
>>   static inline int power_supply_set_property(struct power_supply *psy,
>>   			    enum power_supply_property psp,
>>   			    const union power_supply_propval *val)
>>   { return 0; }
>> +static inline int power_supply_set_property_direct(struct power_supply *psy,
>> +						   enum power_supply_property psp,
>> +						   const union power_supply_propval *val)
>> +{ return 0; }
>>   #endif
>>   extern void power_supply_external_power_changed(struct power_supply *psy);
>>   
>