power: supply: core: Add power_supply_get/set_property_direct()

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>
Acked-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: Hans de Goede <hansg@kernel.org>
Link: https://lore.kernel.org/r/20250627205124.250433-1-W_Armin@gmx.de
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index 33a5bfce4604f012344733ba489eda1c5e8b92c0..cfb0e3e0d4aa0189df2f1a98554379189d21833a 100644 (file)
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -1235,9 +1235,8 @@ 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;
 
@@ -1247,10 +1246,14 @@ 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);
+                       }
                }
        }
 
@@ -1261,20 +1264,49 @@ 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);
@@ -1289,8 +1321,34 @@ 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 7803edaa8ff8dac786a1f1e6e185d8adea0bccfe..0cca01b5607b1ac79766bc0aab7ae16c156c59b8 100644 (file)
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -888,15 +888,23 @@ 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);