Re: [PATCH 1/3] power: supply: core: Add power_supply_get/set_property_direct()
From: Armin Wolf
Date: Sat Jun 28 2025 - 17:34:52 EST
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@xxxxxxxxxx>
Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
Thank you for your work on this.
The entire series looks good to me:
Reviewed-by: Hans de Goede <hansg@xxxxxxxxxx>
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);