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power: supply: core: implement extension API
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Various drivers, mostly in platform/x86 extend the ACPI battery driver
with additional sysfs attributes to implement more UAPIs than are
exposed through ACPI by using various side-channels, like WMI,
nonstandard ACPI or EC communication.

While the created sysfs attributes look similar to the attributes
provided by the powersupply core, there are various deficiencies:

* They don't show up in uevent payload.
* They can't be queried with the standard in-kernel APIs.
* They don't work with triggers.
* The extending driver has to reimplement all of the parsing,
formatting and sysfs display logic.
* Writing a extension driver is completely different from writing a
normal power supply driver.

This extension API avoids all of these issues.
An extension is just a "struct power_supply_ext" with the same kind of
callbacks as in a normal "struct power_supply_desc".

The API is meant to be used via battery_hook_register(), the same way as
the current extensions.

Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Reviewed-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20241211-power-supply-extensions-v6-1-9d9dc3f3d387@weissschuh.net
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
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@t-8ch @sre
t-8ch authored and sre committed Dec 14, 2024
1 parent 57e5a9a commit 6037802
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Showing 4 changed files with 228 additions and 10 deletions.
17 changes: 17 additions & 0 deletions drivers/power/supply/power_supply.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,8 @@
* Modified: 2004, Oct Szabolcs Gyurko
*/

#include <linux/lockdep.h>

struct device;
struct device_type;
struct power_supply;
Expand All @@ -17,6 +19,21 @@ extern int power_supply_property_is_writeable(struct power_supply *psy,
enum power_supply_property psp);
extern bool power_supply_has_property(struct power_supply *psy,
enum power_supply_property psp);
extern bool power_supply_ext_has_property(const struct power_supply_ext *ext,
enum power_supply_property psp);

struct power_supply_ext_registration {
struct list_head list_head;
const struct power_supply_ext *ext;
void *data;
};

/* Make sure that the macro is a single expression */
#define power_supply_for_each_extension(pos, psy) \
if ( ({ lockdep_assert_held(&(psy)->extensions_sem); 0; }) ) \
; \
else \
list_for_each_entry(pos, &(psy)->extensions, list_head) \

#ifdef CONFIG_SYSFS

Expand Down
162 changes: 154 additions & 8 deletions drivers/power/supply/power_supply_core.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -80,13 +80,24 @@ static int __power_supply_changed_work(struct power_supply *pst, void *data)

static void power_supply_changed_work(struct work_struct *work)
{
int ret;
unsigned long flags;
struct power_supply *psy = container_of(work, struct power_supply,
changed_work);

dev_dbg(&psy->dev, "%s\n", __func__);

spin_lock_irqsave(&psy->changed_lock, flags);

if (unlikely(psy->update_groups)) {
psy->update_groups = false;
spin_unlock_irqrestore(&psy->changed_lock, flags);
ret = sysfs_update_groups(&psy->dev.kobj, power_supply_dev_type.groups);
if (ret)
dev_warn(&psy->dev, "failed to update sysfs groups: %pe\n", ERR_PTR(ret));
spin_lock_irqsave(&psy->changed_lock, flags);
}

/*
* Check 'changed' here to avoid issues due to race between
* power_supply_changed() and this routine. In worst case
Expand Down Expand Up @@ -1208,28 +1219,56 @@ static bool psy_desc_has_property(const struct power_supply_desc *psy_desc,
return found;
}

bool power_supply_ext_has_property(const struct power_supply_ext *psy_ext,
enum power_supply_property psp)
{
int i;

for (i = 0; i < psy_ext->num_properties; i++)
if (psy_ext->properties[i] == psp)
return true;

return false;
}

bool power_supply_has_property(struct power_supply *psy,
enum power_supply_property psp)
{
struct power_supply_ext_registration *reg;

if (psy_desc_has_property(psy->desc, psp))
return true;

if (power_supply_battery_info_has_prop(psy->battery_info, psp))
return true;

power_supply_for_each_extension(reg, psy) {
if (power_supply_ext_has_property(reg->ext, psp))
return true;
}

return false;
}

int power_supply_get_property(struct power_supply *psy,
enum power_supply_property psp,
union power_supply_propval *val)
{
struct power_supply_ext_registration *reg;

if (atomic_read(&psy->use_cnt) <= 0) {
if (!psy->initialized)
return -EAGAIN;
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))
return reg->ext->get_property(psy, reg->ext, reg->data, psp, val);
}
}

if (psy_desc_has_property(psy->desc, psp))
return psy->desc->get_property(psy, psp, val);
else if (power_supply_battery_info_has_prop(psy->battery_info, psp))
Expand All @@ -1243,7 +1282,24 @@ int power_supply_set_property(struct power_supply *psy,
enum power_supply_property psp,
const union power_supply_propval *val)
{
if (atomic_read(&psy->use_cnt) <= 0 || !psy->desc->set_property)
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 (reg->ext->set_property)
return reg->ext->set_property(psy, reg->ext, reg->data,
psp, val);
else
return -ENODEV;
}
}
}

if (!psy->desc->set_property)
return -ENODEV;

return psy->desc->set_property(psy, psp, val);
Expand All @@ -1253,7 +1309,22 @@ EXPORT_SYMBOL_GPL(power_supply_set_property);
int power_supply_property_is_writeable(struct power_supply *psy,
enum power_supply_property psp)
{
return psy->desc->property_is_writeable && psy->desc->property_is_writeable(psy, psp);
struct power_supply_ext_registration *reg;

power_supply_for_each_extension(reg, psy) {
if (power_supply_ext_has_property(reg->ext, psp)) {
if (reg->ext->property_is_writeable)
return reg->ext->property_is_writeable(psy, reg->ext,
reg->data, psp);
else
return 0;
}
}

if (!psy->desc->property_is_writeable)
return 0;

return psy->desc->property_is_writeable(psy, psp);
}

void power_supply_external_power_changed(struct power_supply *psy)
Expand All @@ -1272,6 +1343,76 @@ int power_supply_powers(struct power_supply *psy, struct device *dev)
}
EXPORT_SYMBOL_GPL(power_supply_powers);

static int power_supply_update_sysfs_and_hwmon(struct power_supply *psy)
{
unsigned long flags;

spin_lock_irqsave(&psy->changed_lock, flags);
psy->update_groups = true;
spin_unlock_irqrestore(&psy->changed_lock, flags);

power_supply_changed(psy);

power_supply_remove_hwmon_sysfs(psy);
return power_supply_add_hwmon_sysfs(psy);
}

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

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

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

for (i = 0; i < ext->num_properties; i++)
if (power_supply_has_property(psy, ext->properties[i]))
return -EEXIST;

reg = kmalloc(sizeof(*reg), GFP_KERNEL);
if (!reg)
return -ENOMEM;

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

ret = power_supply_update_sysfs_and_hwmon(psy);
if (ret)
goto sysfs_hwmon_failed;

return 0;

sysfs_hwmon_failed:
list_del(&reg->list_head);
kfree(reg);
return ret;
}
EXPORT_SYMBOL_GPL(power_supply_register_extension);

void power_supply_unregister_extension(struct power_supply *psy, const struct power_supply_ext *ext)
{
struct power_supply_ext_registration *reg;

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

power_supply_for_each_extension(reg, psy) {
if (reg->ext == ext) {
list_del(&reg->list_head);
kfree(reg);
power_supply_update_sysfs_and_hwmon(psy);
return;
}
}

dev_warn(&psy->dev, "Trying to unregister invalid extension");
}
EXPORT_SYMBOL_GPL(power_supply_unregister_extension);

static void power_supply_dev_release(struct device *dev)
{
struct power_supply *psy = to_power_supply(dev);
Expand Down Expand Up @@ -1426,6 +1567,9 @@ __power_supply_register(struct device *parent,
}

spin_lock_init(&psy->changed_lock);
init_rwsem(&psy->extensions_sem);
INIT_LIST_HEAD(&psy->extensions);

rc = device_add(dev);
if (rc)
goto device_add_failed;
Expand All @@ -1438,13 +1582,15 @@ __power_supply_register(struct device *parent,
if (rc)
goto register_thermal_failed;

rc = power_supply_create_triggers(psy);
if (rc)
goto create_triggers_failed;
scoped_guard(rwsem_read, &psy->extensions_sem) {
rc = power_supply_create_triggers(psy);
if (rc)
goto create_triggers_failed;

rc = power_supply_add_hwmon_sysfs(psy);
if (rc)
goto add_hwmon_sysfs_failed;
rc = power_supply_add_hwmon_sysfs(psy);
if (rc)
goto add_hwmon_sysfs_failed;
}

/*
* Update use_cnt after any uevents (most notably from device_add()).
Expand Down
26 changes: 24 additions & 2 deletions drivers/power/supply/power_supply_sysfs.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -299,6 +299,27 @@ static ssize_t power_supply_show_enum_with_available(
return count;
}

static ssize_t power_supply_show_charge_behaviour(struct device *dev,
struct power_supply *psy,
union power_supply_propval *value,
char *buf)
{
struct power_supply_ext_registration *reg;

scoped_guard(rwsem_read, &psy->extensions_sem) {
power_supply_for_each_extension(reg, psy) {
if (power_supply_ext_has_property(reg->ext,
POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR))
return power_supply_charge_behaviour_show(dev,
reg->ext->charge_behaviours,
value->intval, buf);
}
}

return power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
value->intval, buf);
}

static ssize_t power_supply_format_property(struct device *dev,
bool uevent,
struct device_attribute *attr,
Expand Down Expand Up @@ -338,8 +359,7 @@ static ssize_t power_supply_format_property(struct device *dev,
case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
if (uevent) /* no possible values in uevents */
goto default_format;
ret = power_supply_charge_behaviour_show(dev, psy->desc->charge_behaviours,
value.intval, buf);
ret = power_supply_show_charge_behaviour(dev, psy, &value, buf);
break;
case POWER_SUPPLY_PROP_CHARGE_TYPES:
if (uevent) /* no possible values in uevents */
Expand Down Expand Up @@ -422,6 +442,8 @@ static umode_t power_supply_attr_is_visible(struct kobject *kobj,
if (attrno == POWER_SUPPLY_PROP_TYPE)
return mode;

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

if (power_supply_has_property(psy, attrno)) {
if (power_supply_property_is_writeable(psy, attrno) > 0)
mode |= S_IWUSR;
Expand Down
33 changes: 33 additions & 0 deletions include/linux/power_supply.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -15,6 +15,8 @@
#include <linux/device.h>
#include <linux/workqueue.h>
#include <linux/leds.h>
#include <linux/rwsem.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/notifier.h>

Expand Down Expand Up @@ -283,6 +285,27 @@ struct power_supply_desc {
int use_for_apm;
};

struct power_supply_ext {
u8 charge_behaviours;
const enum power_supply_property *properties;
size_t num_properties;

int (*get_property)(struct power_supply *psy,
const struct power_supply_ext *ext,
void *data,
enum power_supply_property psp,
union power_supply_propval *val);
int (*set_property)(struct power_supply *psy,
const struct power_supply_ext *ext,
void *data,
enum power_supply_property psp,
const union power_supply_propval *val);
int (*property_is_writeable)(struct power_supply *psy,
const struct power_supply_ext *ext,
void *data,
enum power_supply_property psp);
};

struct power_supply {
const struct power_supply_desc *desc;

Expand All @@ -302,10 +325,13 @@ struct power_supply {
struct delayed_work deferred_register_work;
spinlock_t changed_lock;
bool changed;
bool update_groups;
bool initialized;
bool removing;
atomic_t use_cnt;
struct power_supply_battery_info *battery_info;
struct rw_semaphore extensions_sem; /* protects "extensions" */
struct list_head extensions;
#ifdef CONFIG_THERMAL
struct thermal_zone_device *tzd;
struct thermal_cooling_device *tcd;
Expand Down Expand Up @@ -882,6 +908,13 @@ devm_power_supply_register(struct device *parent,
extern void power_supply_unregister(struct power_supply *psy);
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,
void *data);
extern void power_supply_unregister_extension(struct power_supply *psy,
const struct power_supply_ext *ext);

#define to_power_supply(device) container_of(device, struct power_supply, dev)

extern void *power_supply_get_drvdata(struct power_supply *psy);
Expand Down

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