[PATCH v6 4/4] power: supply: core: add UAPI to discover currently used extensions

From: Thomas Weißschuh
Date: Wed Dec 11 2024 - 14:58:31 EST

Userspace wants to now about the used power supply extensions,
for example to handle a device extended by a certain extension
differently or to discover information about the extending device.

Add a sysfs directory to the power supply device.
This directory contains links which are named after the used extension
and point to the device implementing that extension.

Signed-off-by: Thomas Weißschuh <linux@xxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-class-power | 9 +++++++++
drivers/power/supply/cros_charge-control.c | 5 ++++-
drivers/power/supply/power_supply.h | 2 ++
drivers/power/supply/power_supply_core.c | 19 +++++++++++++++++--
drivers/power/supply/power_supply_sysfs.c | 10 ++++++++++
drivers/power/supply/test_power.c | 4 +++-
include/linux/power_supply.h | 2 ++
7 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-class-power b/Documentation/ABI/testing/sysfs-class-power
index 45180b62d42686c8999eda54f38435cb6c74a879..31e8b33d849cbe99dc93a4ba3723a43440ac3103 100644
--- a/Documentation/ABI/testing/sysfs-class-power
+++ b/Documentation/ABI/testing/sysfs-class-power
@@ -793,3 +793,12 @@ Description:

Access: Read
Valid values: 1-31
+
+What: /sys/class/power_supply/<supply_name>/extensions/<extension_name>
+Date: March 2025
+Contact: linux-pm@xxxxxxxxxxxxxxx
+Description:
+ Reports the extensions registered to the power supply.
+ Each entry is a link to the device which registered the extension.
+
+ Access: Read
diff --git a/drivers/power/supply/cros_charge-control.c b/drivers/power/supply/cros_charge-control.c
index fb4af232721dec1d4f0090f6616922848812b2a2..02d5bdbe2e8d45108dd8f2d3ab6a927b94864b9e 100644
--- a/drivers/power/supply/cros_charge-control.c
+++ b/drivers/power/supply/cros_charge-control.c
@@ -31,6 +31,7 @@
*/

struct cros_chctl_priv {
+ struct device *dev;
struct cros_ec_device *cros_ec;
struct acpi_battery_hook battery_hook;
struct power_supply *hooked_battery;
@@ -202,6 +203,7 @@ static int cros_chctl_psy_prop_is_writeable(struct power_supply *psy,
}; \
\
static const struct power_supply_ext _name = { \
+ .name = "cros-charge-control", \
.properties = _name ## _props, \
.num_properties = ARRAY_SIZE(_name ## _props), \
.charge_behaviours = EC_CHARGE_CONTROL_BEHAVIOURS, \
@@ -233,7 +235,7 @@ static int cros_chctl_add_battery(struct power_supply *battery, struct acpi_batt
return 0;

priv->hooked_battery = battery;
- return power_supply_register_extension(battery, priv->psy_ext, priv);
+ return power_supply_register_extension(battery, priv->psy_ext, priv->dev, priv);
}

static int cros_chctl_remove_battery(struct power_supply *battery, struct acpi_battery_hook *hook)
@@ -299,6 +301,7 @@ static int cros_chctl_probe(struct platform_device *pdev)

dev_dbg(dev, "Command version: %u\n", (unsigned int)priv->cmd_version);

+ priv->dev = dev;
priv->cros_ec = cros_ec;

if (priv->cmd_version == 1)
diff --git a/drivers/power/supply/power_supply.h b/drivers/power/supply/power_supply.h
index 531785516d2ac31f9a7f73a58e15e64cb81820ed..9ed749cd09369f0f13017847687509736b30aae8 100644
--- a/drivers/power/supply/power_supply.h
+++ b/drivers/power/supply/power_supply.h
@@ -25,6 +25,7 @@ extern bool power_supply_ext_has_property(const struct power_supply_ext *ext,
struct power_supply_ext_registration {
struct list_head list_head;
const struct power_supply_ext *ext;
+ struct device *dev;
void *data;
};

@@ -39,6 +40,7 @@ struct power_supply_ext_registration {

extern void __init power_supply_init_attrs(void);
extern int power_supply_uevent(const struct device *dev, struct kobj_uevent_env *env);
+extern const struct attribute_group power_supply_extension_group;
extern const struct attribute_group *power_supply_attr_groups[];

#else
diff --git a/drivers/power/supply/power_supply_core.c b/drivers/power/supply/power_supply_core.c
index bc22edbd0e6a02c27500132075f5c98d814a7330..5142fbd580ee3d629a2aae7d0b9bcd5709162129 100644
--- a/drivers/power/supply/power_supply_core.c
+++ b/drivers/power/supply/power_supply_core.c
@@ -1346,17 +1346,21 @@ static int power_supply_update_sysfs_and_hwmon(struct power_supply *psy)
}

int power_supply_register_extension(struct power_supply *psy, const struct power_supply_ext *ext,
- void *data)
+ struct device *dev, void *data)
{
struct power_supply_ext_registration *reg;
size_t i;
int ret;

- if (!psy || !ext || !ext->properties || !ext->num_properties)
+ if (!psy || !dev || !ext || !ext->name || !ext->properties || !ext->num_properties)
return -EINVAL;

guard(rwsem_write)(&psy->extensions_sem);

+ power_supply_for_each_extension(reg, psy)
+ if (strcmp(ext->name, reg->ext->name) == 0)
+ return -EEXIST;
+
for (i = 0; i < ext->num_properties; i++)
if (power_supply_has_property(psy, ext->properties[i]))
return -EEXIST;
@@ -1366,9 +1370,15 @@ int power_supply_register_extension(struct power_supply *psy, const struct power
return -ENOMEM;

reg->ext = ext;
+ reg->dev = dev;
reg->data = data;
list_add(&reg->list_head, &psy->extensions);

+ ret = sysfs_add_link_to_group(&psy->dev.kobj, power_supply_extension_group.name,
+ &dev->kobj, ext->name);
+ if (ret)
+ goto sysfs_link_failed;
+
ret = power_supply_update_sysfs_and_hwmon(psy);
if (ret)
goto sysfs_hwmon_failed;
@@ -1376,6 +1386,8 @@ int power_supply_register_extension(struct power_supply *psy, const struct power
return 0;

sysfs_hwmon_failed:
+ sysfs_remove_link_from_group(&psy->dev.kobj, power_supply_extension_group.name, ext->name);
+sysfs_link_failed:
list_del(&reg->list_head);
kfree(reg);
return ret;
@@ -1392,6 +1404,9 @@ void power_supply_unregister_extension(struct power_supply *psy, const struct po
if (reg->ext == ext) {
list_del(&reg->list_head);
kfree(reg);
+ sysfs_remove_link_from_group(&psy->dev.kobj,
+ power_supply_extension_group.name,
+ reg->ext->name);
power_supply_update_sysfs_and_hwmon(psy);
return;
}
diff --git a/drivers/power/supply/power_supply_sysfs.c b/drivers/power/supply/power_supply_sysfs.c
index 927ddb9d83bb7259809ba695cb9398d1ad654b46..aadc41ca741d8acd27a83f6bd01d578d7877e7c2 100644
--- a/drivers/power/supply/power_supply_sysfs.c
+++ b/drivers/power/supply/power_supply_sysfs.c
@@ -421,8 +421,18 @@ static const struct attribute_group power_supply_attr_group = {
.is_visible = power_supply_attr_is_visible,
};

+static struct attribute *power_supply_extension_attrs[] = {
+ NULL
+};
+
+const struct attribute_group power_supply_extension_group = {
+ .name = "extensions",
+ .attrs = power_supply_extension_attrs,
+};
+
const struct attribute_group *power_supply_attr_groups[] = {
&power_supply_attr_group,
+ &power_supply_extension_group,
NULL
};

diff --git a/drivers/power/supply/test_power.c b/drivers/power/supply/test_power.c
index 66f9ef52e0f3e6e6e6bebcfd438c2acd421284ec..2a975a110f4859a77f7689369675f2008816d704 100644
--- a/drivers/power/supply/test_power.c
+++ b/drivers/power/supply/test_power.c
@@ -293,6 +293,7 @@ static int test_power_battery_extproperty_is_writeable(struct power_supply *psy,
}

static const struct power_supply_ext test_power_battery_ext = {
+ .name = "test_power",
.properties = test_power_battery_extprops,
.num_properties = ARRAY_SIZE(test_power_battery_extprops),
.get_property = test_power_battery_extget_property,
@@ -307,7 +308,8 @@ static void test_power_configure_battery_extension(bool enable)
psy = test_power_supplies[TEST_BATTERY];

if (enable) {
- if (power_supply_register_extension(psy, &test_power_battery_ext, NULL)) {
+ if (power_supply_register_extension(psy, &test_power_battery_ext, &psy->dev,
+ NULL)) {
pr_err("registering battery extension failed\n");
return;
}
diff --git a/include/linux/power_supply.h b/include/linux/power_supply.h
index e434516086f032cdb4698005bb1a99eda303a307..88a7bd34c8a74d694013aaaebd30269b30509e8b 100644
--- a/include/linux/power_supply.h
+++ b/include/linux/power_supply.h
@@ -284,6 +284,7 @@ struct power_supply_desc {
};

struct power_supply_ext {
+ const char *const name;
u8 charge_behaviours;
const enum power_supply_property *properties;
size_t num_properties;
@@ -907,6 +908,7 @@ extern int power_supply_powers(struct power_supply *psy, struct device *dev);
extern int __must_check
power_supply_register_extension(struct power_supply *psy,
const struct power_supply_ext *ext,
+ struct device *dev,
void *data);
extern void power_supply_unregister_extension(struct power_supply *psy,
const struct power_supply_ext *ext);

--
2.47.1