Re: [PATCH v12 13/16] platform/x86: lenovo-wmi-other: Add WMI battery charge limiting

From: Rong Zhang

Date: Mon May 11 2026 - 11:50:39 EST


Hi Derek,

I am a little busy these days, sorry for not reviewing your series in
time.

On Sun, 2026-05-10 at 04:25 +0000, Derek J. Clark wrote:
> Add charge_behaviour and charge_control_end_threshold attributes through
> a power supply extension for devices that support WMI based charge enable
> & disable.
>
> Lenovo Legion devices that implement WMI function and capdata ID
> 0x03010001 in their BIOS are able to enable or disable charging at 80%
> through the lenovo-wmi-other interface. Add a charge_control_end_threshold
> attribute for BATX devices to expose this capability. The GET method for
> this attribute is bugged. After analyzing the DSDT and some testing it
> appears the method grabs bit(3) instead of bit(4) from the EC register
> that stores the current status, and will only report if charging has
> been inhibited or not. To work around this, store and report the last
> setting written to the attribute.

You said "the GET method for charge_control_end_threshold is bugged"
here, but your code applied the workaround to charge_behaviour. Which is
the bugged one?

>
> Additionally, devices that support WMI function and capdata ID 0x03020000
> are able to force discharge of the battery. Expose this capability with
> a charge_behaviour attribute in the power supply extension, with the
> AUTO and FORCE_DISCHARGE behaviors enabled.
>
> As some devices only expose one attribute or the other, a bitmask is
> added with a lookup table and some helper macros to select the correct
> configuration for the hardware at runtime.
>
> The ideapad_laptop driver provides the charge_type attribute to provide
> similar functionality. When the WMI method is set this can corrupt the
> ACPI method return and cause hardware and driver errors. To avoid
> conflicts between the drivers, we get the acpi_handle and do the same
> check that ideapad_laptop does when it enables the feature. If the
> feature is supported in ideapad_laptop, abort adding the extension from
> lenovo-wmi-other. The ACPI method is more reliable when both are
> present, from my testing, so we can prefer that implementation and do
> not need to worry about de-conflicting from inside that driver. A new
> module parameter, force_load_psy_ext, is provided to bypass this ACPI
> check, as well as feature supported checks, if desired.
>
> Signed-off-by: Derek J. Clark <derekjohn.clark@xxxxxxxxx>
> ---
> v12:
> - Move force_load_psy_ext into its own patch after this.
> - Use correct type casting for args in new funtions.
> - Remove extra parenthesis.
> v11:
> - Refactor to use charge_behaviour and charge_control_end_threshold,
> per the class documentation. The ideapad_laptop driver will be fixed
> in a separate patch series.
> - Due to the extensive refactoring, I have removed the reviewed-by
> tags from Rong and Mark to allow them to recertify the code in its
> current state.
> v7:
> - Use devm_battery_hook_register, manually unregister during unbind.
> v6:
> - Check feature flags to determine if the extension should be loaded
> and if it is writable.
> - Zero initialize wmi_method_args_32.
> - Fix formatting.
> v5:
> - Use switch statement instead of if for battery charge state set/get.
> - use force_load_psy_ext to skip all ACPI interactions.
> - Various formatting fixes.
> v4:
> - Remove unused defines.
> - Disambiguate charging defines by renaming them to be more consistent
> with the kernel modes they represent.
> - Add module parameter to ignore ACPI checks.
> - Don't fail if the ACPI handle isn't found, skip the ACPI check
> instead.
> ---
> drivers/platform/x86/lenovo/Kconfig | 1 +
> drivers/platform/x86/lenovo/wmi-capdata.h | 1 +
> drivers/platform/x86/lenovo/wmi-other.c | 388 ++++++++++++++++++++++
> 3 files changed, 390 insertions(+)
>
> diff --git a/drivers/platform/x86/lenovo/Kconfig b/drivers/platform/x86/lenovo/Kconfig
> index 09b1b055d2e0..b9a5d18caa1e 100644
> --- a/drivers/platform/x86/lenovo/Kconfig
> +++ b/drivers/platform/x86/lenovo/Kconfig
> @@ -262,6 +262,7 @@ config LENOVO_WMI_GAMEZONE
> config LENOVO_WMI_TUNING
> tristate "Lenovo Other Mode WMI Driver"
> depends on ACPI_WMI
> + depends on ACPI_BATTERY
> select HWMON
> select FW_ATTR_CLASS
> select LENOVO_WMI_CAPDATA
> diff --git a/drivers/platform/x86/lenovo/wmi-capdata.h b/drivers/platform/x86/lenovo/wmi-capdata.h
> index a7cfdeaa58f7..a49229cec245 100644
> --- a/drivers/platform/x86/lenovo/wmi-capdata.h
> +++ b/drivers/platform/x86/lenovo/wmi-capdata.h
> @@ -21,6 +21,7 @@
> enum lwmi_device_id {
> LWMI_DEVICE_ID_CPU = 0x01,
> LWMI_DEVICE_ID_GPU = 0x02,
> + LWMI_DEVICE_ID_PSU = 0x03,
> LWMI_DEVICE_ID_FAN = 0x04,
> };
>
> diff --git a/drivers/platform/x86/lenovo/wmi-other.c b/drivers/platform/x86/lenovo/wmi-other.c
> index 1cd2bb5244d2..4d95a9109f5e 100644
> --- a/drivers/platform/x86/lenovo/wmi-other.c
> +++ b/drivers/platform/x86/lenovo/wmi-other.c
> @@ -41,9 +41,12 @@
> #include <linux/limits.h>
> #include <linux/module.h>
> #include <linux/platform_profile.h>
> +#include <linux/power_supply.h>
> #include <linux/types.h>
> #include <linux/wmi.h>
>
> +#include <acpi/battery.h>
> +
> #include "wmi-capdata.h"
> #include "wmi-events.h"
> #include "wmi-helpers.h"
> @@ -75,9 +78,15 @@ enum lwmi_feature_id_gpu {
> LWMI_FEATURE_ID_GPU_NV_CPU_BOOST = 0x0b,
> };
>
> +enum lwmi_feature_id_psu {
> + LWMI_FEATURE_ID_PSU_CHARGE_END_THRESHOLD = 0x01,
> + LWMI_FEATURE_ID_PSU_CHARGE_BEHAVIOR = 0x02,
> +};
> +
> #define LWMI_FEATURE_ID_FAN_RPM 0x03
>
> #define LWMI_TYPE_ID_CROSSLOAD 0x01
> +#define LWMI_TYPE_ID_PSU_AC 0x01
>
> #define LWMI_FEATURE_VALUE_GET 17
> #define LWMI_FEATURE_VALUE_SET 18
> @@ -88,10 +97,19 @@ enum lwmi_feature_id_gpu {
>
> #define LWMI_FAN_DIV 100
>
> +#define LWMI_CHARGE_BEHAVIOR_DISCHARGE 0x00
> +#define LWMI_CHARGE_BEHAVIOR_AUTO 0x01
> +#define LWMI_CHARGE_END_100 0x00
> +#define LWMI_CHARGE_END_80 0x01
> +
> #define LWMI_ATTR_ID_FAN_RPM(x) \
> lwmi_attr_id(LWMI_DEVICE_ID_FAN, LWMI_FEATURE_ID_FAN_RPM, \
> LWMI_GZ_THERMAL_MODE_NONE, LWMI_FAN_ID(x))
>
> +#define LWMI_ATTR_ID_PSU(feat, type) \
> + lwmi_attr_id(LWMI_DEVICE_ID_PSU, feat, \
> + LWMI_GZ_THERMAL_MODE_NONE, type)
> +
> #define LWMI_OM_SYSFS_NAME "lenovo-wmi-other"
> #define LWMI_OM_HWMON_NAME "lenovo_wmi_other"
>
> @@ -131,6 +149,11 @@ struct lwmi_om_priv {
> bool capdata00_collected : 1;
> bool capdata_fan_collected : 1;
> } fan_flags;
> +
> + enum power_supply_charge_behaviour charge_behaviour;
> + const struct power_supply_ext *battery_ext;
> + struct acpi_battery_hook battery_hook;
> + bool bh_registered;
> };
>
> /*
> @@ -555,6 +578,368 @@ static void lwmi_om_fan_info_collect_cd_fan(struct device *dev, struct cd_list *
> lwmi_om_hwmon_add(priv);
> }
>
> +/* ======== Power Supply Extension (component: lenovo-wmi-capdata 00) ======== */
> +
> +/**
> + * lwmi_psy_ext_get_prop() - Get a power_supply_ext property
> + * @ps: The battery that was extended
> + * @ext: The extension
> + * @ext_data: Pointer to the lwmi_om_priv drvdata
> + * @prop: The property to read
> + * @val: The value to return
> + *
> + * Writes the given value to the power_supply_ext property
> + *
> + * Return: 0 on success, or an error
> + */
> +static int lwmi_psy_ext_get_prop(struct power_supply *ps,
> + const struct power_supply_ext *ext,
> + void *ext_data,
> + enum power_supply_property prop,
> + union power_supply_propval *val)
> +{
> + struct lwmi_om_priv *priv = ext_data;
> + struct wmi_method_args_32 args = {};
> + u32 retval;
> + int ret;
> +
> + switch (prop) {
> + case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> + /* Reading from BIOS reads the wrong bit. Use cached value */
> + val->intval = priv->charge_behaviour;
> + return 0;
> + case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
> + args.arg0 = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_END_THRESHOLD,
> + LWMI_TYPE_ID_PSU_AC);
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + ret = lwmi_dev_evaluate_int(priv->wdev, 0x0, LWMI_FEATURE_VALUE_GET,
> + (u8 *)&args, sizeof(args),
> + &retval);
> + if (ret)
> + return ret;
> +
> + dev_dbg(&priv->wdev->dev, "Got return value %#x for property %#x\n", retval, prop);
> +
> + switch (retval) {
> + case LWMI_CHARGE_END_80:
> + val->intval = 80;
> + break;
> + case LWMI_CHARGE_END_100:
> + val->intval = 100;
> + break;
> + default:
> + dev_err(&priv->wdev->dev, "Got invalid charge limit value: %#x\n", retval);
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +
> +/**
> + * lwmi_psy_ext_set_prop() - Set a power_supply_ext property
> + * @ps: The battery that was extended
> + * @ext: The extension
> + * @ext_data: Pointer to the lwmi_om_priv drvdata
> + * @prop: The property to write
> + * @val: The value to write
> + *
> + * Writes the given value to the power_supply_ext property
> + *
> + * Return: 0 on success, or an error
> + */
> +static int lwmi_psy_ext_set_prop(struct power_supply *ps,
> + const struct power_supply_ext *ext,
> + void *ext_data,
> + enum power_supply_property prop,
> + const union power_supply_propval *val)
> +{
> + struct lwmi_om_priv *priv = ext_data;
> + struct wmi_method_args_32 args = {};
> +
> + switch (prop) {
> + case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> + args.arg0 = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_BEHAVIOR,
> + LWMI_TYPE_ID_NONE);
> + switch (val->intval) {
> + case POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO:
> + args.arg1 = LWMI_CHARGE_BEHAVIOR_AUTO;
> + break;
> + case POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE:
> + args.arg1 = LWMI_CHARGE_BEHAVIOR_DISCHARGE;
> + break;
> + default:
> + dev_err(&priv->wdev->dev, "Got invalid charge behavior value: %#x\n",
> + val->intval);
> + return -EINVAL;
> + }
> + priv->charge_behaviour = val->intval;

The cache shouldn't be updated if lwmi_dev_evaluate_int() returns an
error, right?

> + break;
> + case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
> + args.arg0 = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_END_THRESHOLD,
> + LWMI_TYPE_ID_PSU_AC);
> + switch (val->intval) {
> + case 0 ... 80:
> + args.arg1 = LWMI_CHARGE_END_80;
> + break;
> + case 81 ... 100:
> + args.arg1 = LWMI_CHARGE_END_100;
> + break;
> + default:
> + dev_err(&priv->wdev->dev, "Got invalid charge limit value: %#x\n",
> + val->intval);
> + return -EINVAL;
> + }
> + break;
> + default:
> + return false;
> + }
> +
> + dev_dbg(&priv->wdev->dev, "Attempting to set %#010x for property %#x to %#x\n",
> + args.arg0, prop, args.arg1);
> +
> + return lwmi_dev_evaluate_int(priv->wdev, 0x0, LWMI_FEATURE_VALUE_SET,
> + (u8 *)&args, sizeof(args), NULL);
> +}
> +
> +/**
> + * lwmi_psy_prop_is_suppported() - Determine if the property is supported
> + * @priv: Pointer to the lwmi_om_priv drvdata
> + * @prop: The power supply property to be evaluated
> + *
> + * Checks capdata 00 to determine if the property is supported.
> + *
> + * Return: true if readable, or false
> + */
> +static bool lwmi_psy_prop_is_supported(struct lwmi_om_priv *priv, enum power_supply_property prop)
> +{
> + struct capdata00 capdata;
> + u32 attribute_id;
> + int ret;
> +
> + switch (prop) {
> + case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> + attribute_id = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_BEHAVIOR,
> + LWMI_TYPE_ID_NONE);
> + break;
> + case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
> + attribute_id = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_END_THRESHOLD,
> + LWMI_TYPE_ID_PSU_AC);
> + break;
> + default:
> + return false;
> + }
> +
> + ret = lwmi_cd00_get_data(priv->cd00_list, attribute_id, &capdata);
> + if (ret)
> + return false;
> +
> + dev_dbg(&priv->wdev->dev, "Battery charge feature (%#010x) support level: %#x\n",
> + attribute_id, capdata.supported);
> +
> + return (capdata.supported & LWMI_SUPP_VALID) && (capdata.supported & LWMI_SUPP_GET);
> +}
> +
> +/**
> + * lwmi_psy_prop_is_writeable() - Determine if the property is writeable
> + * @ps: The battery that was extended
> + * @ext: The extension
> + * @ext_data: Pointer the lwmi_om_priv drvdata
> + * @prop: The property to check
> + *
> + * Checks capdata 00 to determine if the property is writable.
> + *
> + * Return: true if writable, or false
> + */
> +static int lwmi_psy_prop_is_writeable(struct power_supply *ps,
> + const struct power_supply_ext *ext,
> + void *ext_data,
> + enum power_supply_property prop)
> +{
> + struct lwmi_om_priv *priv = ext_data;
> + struct capdata00 capdata;
> + u32 attribute_id;
> + int ret;
> +
> + switch (prop) {
> + case POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR:
> + attribute_id = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_BEHAVIOR,
> + LWMI_TYPE_ID_NONE);
> + break;
> + case POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD:
> + attribute_id = LWMI_ATTR_ID_PSU(LWMI_FEATURE_ID_PSU_CHARGE_END_THRESHOLD,
> + LWMI_TYPE_ID_PSU_AC);
> + break;
> + default:
> + return false;
> + }
> +
> + ret = lwmi_cd00_get_data(priv->cd00_list, attribute_id, &capdata);
> + if (ret)
> + return false;

This shares a lot of lines of code with lwmi_psy_prop_is_supported().
I'd factor the common code into a helper function.

I don't have a strong preference though. It's fine to keep it as is.

> +
> + return !!(capdata.supported & LWMI_SUPP_SET);
> +}
> +
> +static const enum power_supply_property lwmi_psy_ext_props_all[] = {
> + POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR,
> + POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD,
> +};
> +
> +static const enum power_supply_property lwmi_psy_ext_props_threshold[] = {
> + POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD,
> +};
> +
> +static const enum power_supply_property lwmi_psy_ext_props_behaviour[] = {
> + POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR,
> +};
> +
> +#define DEFINE_LWMI_POWER_SUPPLY_EXTENSION(_name, _props, _behaviours) \
> + static const struct power_supply_ext _name = { \
> + .name = LWMI_OM_SYSFS_NAME, \
> + .properties = _props, \
> + .num_properties = ARRAY_SIZE(_props), \
> + .charge_behaviours = _behaviours, \
> + .get_property = lwmi_psy_ext_get_prop, \
> + .set_property = lwmi_psy_ext_set_prop, \
> + .property_is_writeable = lwmi_psy_prop_is_writeable, \
> + }
> +
> +#define LWMI_CHARGE_BEHAVIOURS (BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_AUTO) | \
> + BIT(POWER_SUPPLY_CHARGE_BEHAVIOUR_INHIBIT_CHARGE))

lwmi_psy_ext_get_prop() and lwmi_psy_ext_set_prop() use
POWER_SUPPLY_CHARGE_BEHAVIOUR_FORCE_DISCHARGE. Mismatch.

> +
> +DEFINE_LWMI_POWER_SUPPLY_EXTENSION(lwmi_psy_ext_all, lwmi_psy_ext_props_all,
> + LWMI_CHARGE_BEHAVIOURS);
> +DEFINE_LWMI_POWER_SUPPLY_EXTENSION(lwmi_psy_ext_threshold,
> + lwmi_psy_ext_props_threshold, 0);
> +DEFINE_LWMI_POWER_SUPPLY_EXTENSION(lwmi_psy_ext_behaviour,
> + lwmi_psy_ext_props_behaviour,
> + LWMI_CHARGE_BEHAVIOURS);
> +
> +#define LWMI_PSY_PROP_BEHAVIOUR BIT(0)
> +#define LWMI_PSY_PROP_THRESHOLD BIT(1)
> +
> +static const struct power_supply_ext *lwmi_psy_exts[] = {
> + [LWMI_PSY_PROP_BEHAVIOUR] = &lwmi_psy_ext_behaviour,
> + [LWMI_PSY_PROP_THRESHOLD] = &lwmi_psy_ext_threshold,
> + [LWMI_PSY_PROP_BEHAVIOUR | LWMI_PSY_PROP_THRESHOLD] = &lwmi_psy_ext_all,
> +};
> +
> +/**
> + * lwmi_add_battery() - Connect the power_supply_ext
> + * @battery: The battery to extend
> + * @hook: The driver hook used to extend the battery
> + *
> + * Return: 0 on success, or an error.
> + */
> +static int lwmi_add_battery(struct power_supply *battery, struct acpi_battery_hook *hook)
> +{
> + struct lwmi_om_priv *priv = container_of(hook, struct lwmi_om_priv, battery_hook);
> +
> + return power_supply_register_extension(battery, priv->battery_ext, &priv->wdev->dev, priv);
> +}
> +
> +/**
> + * lwmi_remove_battery() - Disconnect the power_supply_ext
> + * @battery: The battery that was extended
> + * @hook: The driver hook used to extend the battery
> + *
> + * Return: 0 on success, or an error.
> + */
> +static int lwmi_remove_battery(struct power_supply *battery, struct acpi_battery_hook *hook)
> +{
> + struct lwmi_om_priv *priv = container_of(hook, struct lwmi_om_priv, battery_hook);
> +
> + power_supply_unregister_extension(battery, priv->battery_ext);
> + return 0;
> +}
> +
> +/**
> + * lwmi_acpi_match() - Attempts to return the ideapad acpi handle
> + * @handle: The ACPI handle that manages battery charging
> + * @lvl: Unused
> + * @context: Void pointer to the acpi_handle object to return
> + * @retval: Unused
> + *
> + * Checks if the ideapad_laptop driver is going to manage charge_type first,
> + * then if not, hooks the battery to our WMI methods.
> + *
> + * Return: AE_CTRL_TERMINATE if found, AE_OK if not found.
> + */
> +static acpi_status lwmi_acpi_match(acpi_handle handle, u32 lvl,
> + void *context, void **retval)
> +{
> + acpi_handle *ahand = context;
> +
> + if (!handle)
> + return AE_OK;
> +
> + *ahand = handle;
> +
> + return AE_CTRL_TERMINATE;
> +}
> +
> +/**
> + * lwmi_om_psy_ext_init() - Hooks power supply extension to device battery
> + * @priv: Pointer to the lwmi_om_priv drvdata.
> + *
> + * Checks if the ideapad_laptop driver is going to manage charge attributes first,
> + * then if not, hooks the battery to our WMI methods if they are supported.
> + */
> +static void lwmi_om_psy_ext_init(struct lwmi_om_priv *priv)
> +{
> + static const char * const ideapad_hid = "VPC2004";
> + acpi_handle handle = NULL;
> + unsigned int props = 0;
> + int ret;
> +
> + priv->bh_registered = false;

Why do we need this? priv was devm_kzalloc()ed.

> +
> + /* Deconflict ideapad_laptop driver */
> + ret = acpi_get_devices(ideapad_hid, lwmi_acpi_match, &handle, NULL);
> + if (ret)
> + return;
> +
> + if (handle && acpi_has_method(handle, "GBMD") && acpi_has_method(handle, "SBMC")) {
> + dev_dbg(&priv->wdev->dev, "ideapad_laptop driver manages battery for device\n");
> + return;
> + }
> +
> + if (lwmi_psy_prop_is_supported(priv, POWER_SUPPLY_PROP_CHARGE_BEHAVIOUR))
> + props |= LWMI_PSY_PROP_BEHAVIOUR;
> + if (lwmi_psy_prop_is_supported(priv, POWER_SUPPLY_PROP_CHARGE_CONTROL_END_THRESHOLD))
> + props |= LWMI_PSY_PROP_THRESHOLD;
> + if (!props)
> + return;
> +
> + /* Add battery hooks */
> + priv->battery_ext = lwmi_psy_exts[props];
> + priv->battery_hook.add_battery = lwmi_add_battery;
> + priv->battery_hook.remove_battery = lwmi_remove_battery;
> + priv->battery_hook.name = "Lenovo WMI Other Battery Extension";
> + priv->bh_registered = true;

I guess the default charge behavior is auto. If that's the case, let's
initialize priv->charge_behaviour to reflect this, so that it won't
confuse users in most cases.

Thanks,
Rong

> +
> + battery_hook_register(&priv->battery_hook);
> +}
> +
> +/**
> + * lwmi_om_psy_remove() - Unregister battery hook
> + * @priv: Driver private data
> + *
> + * Unregisters the battery hook if applicable.
> + */
> +static void lwmi_om_psy_remove(struct lwmi_om_priv *priv)
> +{
> + if (!priv->bh_registered)
> + return;
> +
> + battery_hook_unregister(&priv->battery_hook);
> + priv->bh_registered = false;
> +}
> +
> /* ======== fw_attributes (component: lenovo-wmi-capdata 01) ======== */
>
> struct tunable_attr_01 {
> @@ -1241,6 +1626,7 @@ static int lwmi_om_master_bind(struct device *dev)
> }
>
> lwmi_om_fan_info_collect_cd00(priv);
> + lwmi_om_psy_ext_init(priv);
>
> lwmi_om_fw_attr_add(priv);
>
> @@ -1263,6 +1649,8 @@ static void lwmi_om_master_unbind(struct device *dev)
>
> lwmi_om_hwmon_remove(priv);
>
> + lwmi_om_psy_remove(priv);
> +
> component_unbind_all(dev, NULL);
> }
>