Re: [PATCH v6 5/7] platform/x86: lenovo-wmi-capdata: Add support for Fan Test Data

[Rong Zhang <i@rong.moe>]

Hi Ilpo,

Thanks for your review.

On Mon, 2025-11-24 at 18:45 +0200, Ilpo Järvinen wrote:
> On Sun, 23 Nov 2025, Rong Zhang wrote:
> 
> > Add support for LENOVO_FAN_TEST_DATA WMI data block. Provides an
> > interface for querying the min/max fan speed RPM (reference data) of a
> > given fan ID.
> > 
> > This interface is optional. Hence, it does not bind to lenovo-wmi-other
> > and is not registered as a component for the moment. Appropriate binding
> > will be implemented in the subsequent patch.
> > 
> > Signed-off-by: Rong Zhang <i@rong.moe>
> > Reviewed-by: Derek J. Clark <derekjohn.clark@gmail.com>
> > Tested-by: Derek J. Clark <derekjohn.clark@gmail.com>
> > ---
> > Changes in v4:
> > - Rebase on top of changes made to [PATCH v4 3/7]
> > - Do not register it as a component until [PATCH v4 6/7]
> > 
> > Changes in v2:
> > - Reword documentation
> > ---
> >  .../wmi/devices/lenovo-wmi-other.rst          |  17 +++
> >  drivers/platform/x86/lenovo/wmi-capdata.c     | 102 ++++++++++++++++++
> >  drivers/platform/x86/lenovo/wmi-capdata.h     |   7 ++
> >  3 files changed, 126 insertions(+)
> > 
> > diff --git a/Documentation/wmi/devices/lenovo-wmi-other.rst b/Documentation/wmi/devices/lenovo-wmi-other.rst
> > index fcad595d49af..821282e07d93 100644
> > --- a/Documentation/wmi/devices/lenovo-wmi-other.rst
> > +++ b/Documentation/wmi/devices/lenovo-wmi-other.rst
> > @@ -62,6 +62,13 @@ The following firmware-attributes are implemented:
> >   - ppt_pl2_sppt: Platform Profile Tracking Slow Package Power Tracking
> >   - ppt_pl3_fppt: Platform Profile Tracking Fast Package Power Tracking
> >  
> > +LENOVO_FAN_TEST_DATA
> > +-------------------------
> > +
> > +WMI GUID ``B642801B-3D21-45DE-90AE-6E86F164FB21``
> > +
> > +The LENOVO_FAN_TEST_DATA interface provides reference data for self-test of
> > +cooling fans.
> >  
> >  WMI interface description
> >  =========================
> > @@ -115,3 +122,13 @@ data using the `bmfdec <https://github.com/pali/bmfdec>`_ utility:
> >      [WmiDataId(3), read, Description("Data Size.")] uint32 DataSize;
> >      [WmiDataId(4), read, Description("Default Value"), WmiSizeIs("DataSize")] uint8 DefaultValue[];
> >    };
> > +
> > +  [WMI, Dynamic, Provider("WmiProv"), Locale("MS\\0x409"), Description("Definition of Fan Test Data"), guid("{B642801B-3D21-45DE-90AE-6E86F164FB21}")]
> > +  class LENOVO_FAN_TEST_DATA {
> > +    [key, read] string InstanceName;
> > +    [read] boolean Active;
> > +    [WmiDataId(1), read, Description("Mode.")] uint32 NumOfFans;
> > +    [WmiDataId(2), read, Description("Fan ID."), WmiSizeIs("NumOfFans")] uint32 FanId[];
> > +    [WmiDataId(3), read, Description("Maximum Fan Speed."), WmiSizeIs("NumOfFans")] uint32 FanMaxSpeed[];
> > +    [WmiDataId(4), read, Description("Minumum Fan Speed."), WmiSizeIs("NumOfFans")] uint32 FanMinSpeed[];
> > +  };
> > diff --git a/drivers/platform/x86/lenovo/wmi-capdata.c b/drivers/platform/x86/lenovo/wmi-capdata.c
> > index 29267c373ab3..e6392357395c 100644
> > --- a/drivers/platform/x86/lenovo/wmi-capdata.c
> > +++ b/drivers/platform/x86/lenovo/wmi-capdata.c
> > @@ -13,6 +13,10 @@
> >   * attribute has multiple pages, one for each of the thermal modes managed by
> >   * the Gamezone interface.
> >   *
> > + * Fan Test Data includes the max/min fan speed RPM for each fan. This is
> > + * reference data for self-test. If the fan is in good condition, it is capable
> > + * to spin faster than max RPM or slower than min RPM.
> > + *
> >   * Copyright (C) 2025 Derek J. Clark <derekjohn.clark@gmail.com>
> >   *   - Initial implementation (formerly named lenovo-wmi-capdata01)
> >   *
> > @@ -41,6 +45,7 @@
> >  
> >  #define LENOVO_CAPABILITY_DATA_00_GUID "362A3AFE-3D96-4665-8530-96DAD5BB300E"
> >  #define LENOVO_CAPABILITY_DATA_01_GUID "7A8F5407-CB67-4D6E-B547-39B3BE018154"
> > +#define LENOVO_FAN_TEST_DATA_GUID "B642801B-3D21-45DE-90AE-6E86F164FB21"
> >  
> >  #define ACPI_AC_CLASS "ac_adapter"
> >  #define ACPI_AC_NOTIFY_STATUS 0x80
> > @@ -48,6 +53,7 @@
> >  enum lwmi_cd_type {
> >  	LENOVO_CAPABILITY_DATA_00,
> >  	LENOVO_CAPABILITY_DATA_01,
> > +	LENOVO_FAN_TEST_DATA,
> >  };
> >  
> >  #define LWMI_CD_TABLE_ITEM(_type)		\
> > @@ -62,6 +68,7 @@ static const struct lwmi_cd_info {
> >  } lwmi_cd_table[] = {
> >  	LWMI_CD_TABLE_ITEM(LENOVO_CAPABILITY_DATA_00),
> >  	LWMI_CD_TABLE_ITEM(LENOVO_CAPABILITY_DATA_01),
> > +	LWMI_CD_TABLE_ITEM(LENOVO_FAN_TEST_DATA),
> >  };
> >  
> >  struct lwmi_cd_priv {
> > @@ -78,6 +85,7 @@ struct cd_list {
> >  	union {
> >  		DECLARE_FLEX_ARRAY(struct capdata00, cd00);
> >  		DECLARE_FLEX_ARRAY(struct capdata01, cd01);
> > +		DECLARE_FLEX_ARRAY(struct capdata_fan, cd_fan);
> >  	};
> >  };
> >  
> > @@ -117,6 +125,10 @@ void lwmi_cd_match_add_all(struct device *master, struct component_match **match
> >  		return;
> >  
> >  	for (i = 0; i < ARRAY_SIZE(lwmi_cd_table); i++) {
> > +		/* Skip optional interfaces. */
> > +		if (lwmi_cd_table[i].type == LENOVO_FAN_TEST_DATA)
> > +			continue;
> > +
> >  		component_match_add(master, matchptr, lwmi_cd_match,
> >  				    (void *)&lwmi_cd_table[i].type);
> >  		if (IS_ERR(*matchptr))
> > @@ -194,6 +206,9 @@ EXPORT_SYMBOL_NS_GPL(lwmi_cd00_get_data, "LENOVO_WMI_CD");
> >  DEF_LWMI_CDXX_GET_DATA(cd01, LENOVO_CAPABILITY_DATA_01, struct capdata01);
> >  EXPORT_SYMBOL_NS_GPL(lwmi_cd01_get_data, "LENOVO_WMI_CD");
> >  
> > +DEF_LWMI_CDXX_GET_DATA(cd_fan, LENOVO_FAN_TEST_DATA, struct capdata_fan);
> > +EXPORT_SYMBOL_NS_GPL(lwmi_cd_fan_get_data, "LENOVO_WMI_CD");
> > +
> >  /**
> >   * lwmi_cd_cache() - Cache all WMI data block information
> >   * @priv: lenovo-wmi-capdata driver data.
> > @@ -217,6 +232,9 @@ static int lwmi_cd_cache(struct lwmi_cd_priv *priv)
> >  		p = &priv->list->cd01[0];
> >  		size = sizeof(priv->list->cd01[0]);
> >  		break;
> > +	case LENOVO_FAN_TEST_DATA:
> > +		/* Done by lwmi_cd_alloc() => lwmi_cd_fan_list_alloc_cache(). */
> > +		return 0;
> >  	default:
> >  		return -EINVAL;
> >  	}
> > @@ -239,6 +257,78 @@ static int lwmi_cd_cache(struct lwmi_cd_priv *priv)
> >  	return 0;
> >  }
> >  
> > +/**
> > + * lwmi_cd_fan_list_alloc_cache() - Alloc and cache Fan Test Data list
> > + * @priv: lenovo-wmi-capdata driver data.
> > + * @listptr: Pointer to returned cd_list pointer.
> > + *
> > + * Return: count of fans found, or an error.
> > + */
> > +static int lwmi_cd_fan_list_alloc_cache(struct lwmi_cd_priv *priv, struct cd_list **listptr)
> > +{
> > +	u32 count, *fan_ids, *fan_min_rpms, *fan_max_rpms;
> > +	union acpi_object *ret_obj __free(kfree) = NULL;
> 
> Since you're using __free(), please move this to where you assign the 
> value. This is to create a pattern with cleanup helpers. The cleanup 
> order depends on the order the variables are introduced which in some 
> other cases may be significant.

Make sense. Will move it to the last declaration lines with its
assignment. Thanks.

> > +	struct block { u32 nr; u32 data[]; } *block;
> 
> This is the first time I see this style anywhere in the kernel's context, 
> has there been some general discussion about this style somewhere?
> 
> At least it seems immediately obvious to me that this style will have a 
> negative impact on documentability due to (too) concise use of space.

Make sense. Will break it into multiple lines. Thanks.

> > +	struct cd_list *list;
> > +	size_t size;
> > +	int idx;
> > +
> > +	ret_obj = wmidev_block_query(priv->wdev, 0);
> > +	if (!ret_obj)
> > +		return -ENODEV;
> > +
> > +	/*
> > +	 * This is usually caused by a dummy ACPI method. Do not return an error
> > +	 * as failing to probe this device will result in master driver being
> > +	 * unbound - this behavior aligns with lwmi_cd_cache().
> > +	 */
> > +	if (ret_obj->type != ACPI_TYPE_BUFFER) {
> > +		count = 0;
> > +		goto alloc;
> > +	}
> > +
> > +	size = ret_obj->buffer.length;
> > +	block = (struct block *)ret_obj->buffer.pointer;
> 
> void * can be cast implicitly.

`ret_obj->buffer.pointer' is a `u8 *' pointer so the cast is mandatory.

Hmmm, this reminds me that `struct block' probably needs a `__packed'
to generate unaligned access to it.

> > +
> > +	count = size >= sizeof(*block) ? block->nr : 0;
> > +	if (size < struct_size(block, data, count * 3)) {
> > +		dev_warn(&priv->wdev->dev,
> > +			 "incomplete fan test data block: %zu < %zu, ignoring\n",
> > +			 size, struct_size(block, data, count * 3));
> > +		count = 0;
> > +	}
> > +
> > +	if (count == 0)
> > +		goto alloc;
> > +
> > +	if (count > U8_MAX) {
> > +		dev_warn(&priv->wdev->dev,
> > +			 "too many fans reported: %u > %u, truncating\n",
> > +			 count, U8_MAX);
> > +		count = U8_MAX;
> > +	}
> > +
> > +	fan_ids = &block->data[0];
> > +	fan_max_rpms = &block->data[count];
> > +	fan_min_rpms = &block->data[count * 2];
> 
> Please rearrange so you can remove the goto:
> 
> 	1. limit count
> 	if (count) {
> 		...
> 	}

Nice catch! Will rearrange. Thanks.

Thanks,
Rong

> > +
> > +alloc:
> > +	list = devm_kzalloc(&priv->wdev->dev, struct_size(list, cd_fan, count), GFP_KERNEL);
> > +	if (!list)
> > +		return -ENOMEM;
> > +
> > +	for (idx = 0; idx < count; idx++) {
> > +		list->cd_fan[idx] = (struct capdata_fan) {
> > +			.id = fan_ids[idx],
> > +			.min_rpm = fan_min_rpms[idx],
> > +			.max_rpm = fan_max_rpms[idx],
> > +		};
> > +	}
> > +
> > +	*listptr = list;
> > +	return count;
> > +}
> > +
> >  /**
> >   * lwmi_cd_alloc() - Allocate a cd_list struct in drvdata
> >   * @priv: lenovo-wmi-capdata driver data.
> > @@ -264,6 +354,12 @@ static int lwmi_cd_alloc(struct lwmi_cd_priv *priv, enum lwmi_cd_type type)
> >  	case LENOVO_CAPABILITY_DATA_01:
> >  		list_size = struct_size(list, cd01, count);
> >  		break;
> > +	case LENOVO_FAN_TEST_DATA:
> > +		count = lwmi_cd_fan_list_alloc_cache(priv, &list);
> > +		if (count < 0)
> > +			return count;
> > +
> > +		goto got_list;
> >  	default:
> >  		return -EINVAL;
> >  	}
> > @@ -272,6 +368,7 @@ static int lwmi_cd_alloc(struct lwmi_cd_priv *priv, enum lwmi_cd_type type)
> >  	if (!list)
> >  		return -ENOMEM;
> >  
> > +got_list:
> >  	ret = devm_mutex_init(&priv->wdev->dev, &list->list_mutex);
> >  	if (ret)
> >  		return ret;
> > @@ -390,6 +487,8 @@ static int lwmi_cd_probe(struct wmi_device *wdev, const void *context)
> >  
> >  		ret = component_add(&wdev->dev, &lwmi_cd_component_ops);
> >  		goto out;
> > +	case LENOVO_FAN_TEST_DATA:
> > +		goto out;
> >  	default:
> >  		return -EINVAL;
> >  	}
> > @@ -413,6 +512,8 @@ static void lwmi_cd_remove(struct wmi_device *wdev)
> >  	case LENOVO_CAPABILITY_DATA_01:
> >  		component_del(&wdev->dev, &lwmi_cd_component_ops);
> >  		break;
> > +	case LENOVO_FAN_TEST_DATA:
> > +		break;
> >  	default:
> >  		WARN_ON(1);
> >  	}
> > @@ -425,6 +526,7 @@ static void lwmi_cd_remove(struct wmi_device *wdev)
> >  static const struct wmi_device_id lwmi_cd_id_table[] = {
> >  	{ LWMI_CD_WDEV_ID(LENOVO_CAPABILITY_DATA_00) },
> >  	{ LWMI_CD_WDEV_ID(LENOVO_CAPABILITY_DATA_01) },
> > +	{ LWMI_CD_WDEV_ID(LENOVO_FAN_TEST_DATA) },
> >  	{}
> >  };
> >  
> > diff --git a/drivers/platform/x86/lenovo/wmi-capdata.h b/drivers/platform/x86/lenovo/wmi-capdata.h
> > index a6d006ef458f..38af4c4e4ef4 100644
> > --- a/drivers/platform/x86/lenovo/wmi-capdata.h
> > +++ b/drivers/platform/x86/lenovo/wmi-capdata.h
> > @@ -26,6 +26,12 @@ struct capdata01 {
> >  	u32 max_value;
> >  };
> >  
> > +struct capdata_fan {
> > +	u32 id;
> > +	u32 min_rpm;
> > +	u32 max_rpm;
> > +};
> > +
> >  struct lwmi_cd_binder {
> >  	struct cd_list *cd00_list;
> >  	struct cd_list *cd01_list;
> > @@ -34,5 +40,6 @@ struct lwmi_cd_binder {
> >  void lwmi_cd_match_add_all(struct device *master, struct component_match **matchptr);
> >  int lwmi_cd00_get_data(struct cd_list *list, u32 attribute_id, struct capdata00 *output);
> >  int lwmi_cd01_get_data(struct cd_list *list, u32 attribute_id, struct capdata01 *output);
> > +int lwmi_cd_fan_get_data(struct cd_list *list, u32 attribute_id, struct capdata_fan *output);
> >  
> >  #endif /* !_LENOVO_WMI_CAPDATA_H_ */
> >