Re: [PATCH v4 4/8] platform/x86: lenovo-wmi-other: Limit adding attributes to supported devices

[Derek J. Clark]

On March 14, 2026 6:26:08 PM PDT, Rong Zhang <i@xxxxxxxx> wrote:
>Hi Derek,
>
>On Thu, 2026-03-12 at 03:10 +0000, Derek J. Clark wrote:
>> Adds lwmi_is_attr_01_supported, and only creates the attribute subfolder
>> if the attribute is supported by the hardware. Due to some poorly
>> implemented BIOS this is a multi-step sequence of events. This is
>> because:
>> - Some BIOS support getting the capability data from custom mode (0xff),
>>   while others only support it in no-mode (0x00).
>> - Some BIOS support get/set for the current value from custom mode (0xff),
>>   while others only support it in no-mode (0x00).
>> - Some BIOS report capability data for a method that is not fully
>>   implemented.
>> - Some BIOS have methods fully implemented, but no complimentary
>>   capability data.
>> 
>> To ensure we only expose fully implemented methods with corresponding
>> capability data, we check each outcome before reporting that an
>> attribute can be supported.
>> 
>> Checking for lwmi_is_attr_01_supported during remove is not done to
>> ensure that we don't attempt to call cd01 or send WMI events if one of
>> the interfaces being removed was the cause of the driver unloading.
>> 
>> Reviewed-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>
>> Reported-by: Kurt Borja <kuurtb@xxxxxxxxx>
>> Closes: https://lore.kernel.org/platform-driver-x86/DG60P3SHXR8H.3NSEHMZ6J7XRC@xxxxxxxxx/
>> Signed-off-by: Derek J. Clark <derekjohn.clark@xxxxxxxxx>
>> ---
>> v4:
>>   - Use for loop instead of backtrace gotos for checking if an attribute
>>     is supported.
>>   - Add include for dev_printk.
>>   - Wrap dev_dbg in lwmi_is_attr_01_supported earlier.
>>   - Don't use symmetric cleanup of attributes in error states.
>> ---
>>  drivers/platform/x86/lenovo/wmi-other.c | 76 ++++++++++++++++++++++++-
>>  1 file changed, 74 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/platform/x86/lenovo/wmi-other.c b/drivers/platform/x86/lenovo/wmi-other.c
>> index 9fff9c1f768c..55a26e5617d4 100644
>> --- a/drivers/platform/x86/lenovo/wmi-other.c
>> +++ b/drivers/platform/x86/lenovo/wmi-other.c
>> @@ -32,6 +32,7 @@
>>  #include <linux/component.h>
>>  #include <linux/container_of.h>
>>  #include <linux/device.h>
>> +#include <linux/dev_printk.h>
>>  #include <linux/export.h>
>>  #include <linux/gfp_types.h>
>>  #include <linux/hwmon.h>
>> @@ -871,6 +872,76 @@ static ssize_t attr_current_value_show(struct kobject *kobj,
>>  	return sysfs_emit(buf, "%d\n", retval);
>>  }
>>  
>> +/**
>> + * lwmi_attr_01_is_supported() - Determine if the given attribute is supported.
>> + * @tunable_attr: The attribute to verify.
>> + *
>> + * First check if the attribute has a corresponding capdata01 table in the cd01
>> + * module under the "custom" mode (0xff). If that is not present then check if
>> + * there is a corresponding "no-mode" (0x00) entry. If either of those passes,
>> + * check capdata->supported for values > 0. If capdata is available, attempt to
>> + * determine the set/get mode for the current value property using a similar
>> + * pattern. If the value returned by either custom or no-mode is 0, or we get
>> + * an error, we assume that mode is not supported. If any of the above checks
>> + * fail then the attribute is not fully supported.
>> + *
>> + * The probed cd_mode_id/cv_mode_id are stored on the tunable_attr for later
>> + * reference.
>> + *
>> + * Return: Support level, or an error code.
>> + */
>> +static int lwmi_attr_01_is_supported(struct tunable_attr_01 *tunable_attr)
>> +{
>> +	u8 modes[2] = { LWMI_GZ_THERMAL_MODE_CUSTOM, LWMI_GZ_THERMAL_MODE_NONE };
>> +	struct lwmi_om_priv *priv = dev_get_drvdata(tunable_attr->dev);
>> +	struct wmi_method_args_32 args;
>> +	bool cd_mode_found = false;
>> +	bool cv_mode_found = false;
>> +	struct capdata01 capdata;
>> +	int retval, ret, i;
>> +
>> +	/* Determine tunable_attr->cd_mode_id*/
>> +	for (i = 0; i < ARRAY_SIZE(modes); i++) {
>
>#include <linux/array_size.h>
>
>> +		args.arg0 = lwmi_attr_id(tunable_attr->device_id, tunable_attr->feature_id,
>> +					 modes[i], tunable_attr->type_id);
>> +
>> +		ret = lwmi_cd01_get_data(priv->cd01_list, args.arg0, &capdata);
>> +		if (ret || !capdata.supported)
>> +			continue;
>> +		tunable_attr->cd_mode_id = modes[i];
>> +		cd_mode_found = true;
>> +		break;
>> +	}
>> +
>> +	if (!cd_mode_found)
>> +		return -EOPNOTSUPP;
>> +
>> +	/* Determine tunable_attr->cv_mode_id, returns 1 if supported*/
>> +	for (i = 0; i < ARRAY_SIZE(modes); i++) {
>> +		args.arg0 = lwmi_attr_id(tunable_attr->device_id, tunable_attr->feature_id,
>> +					 modes[i], tunable_attr->type_id);
>> +
>> +		ret = lwmi_dev_evaluate_int(priv->wdev, 0x0, LWMI_FEATURE_VALUE_GET,
>> +					    (unsigned char *)&args, sizeof(args),
>> +					    &retval);
>> +		if (ret || !retval)
>> +			continue;
>> +		tunable_attr->cv_mode_id = modes[i];
>> +		cv_mode_found = true;
>> +		break;
>> +	}
>> +
>> +	if (!cv_mode_found)
>> +		return -EOPNOTSUPP;
>> +
>> +	dev_dbg(tunable_attr->dev,
>> +		"cd_mode_id: %02x%02x%02x%02x, cv_mode_id: %#08x attribute support level: %x\n",
>                             ^                               ^  ^                          ^
>> +		tunable_attr->device_id, tunable_attr->feature_id, tunable_attr->cd_mode_id,
>> +		tunable_attr->type_id, args.arg0, capdata.supported);
>                ^
>
>	dev_dbg(tunable_attr->dev,
>		"cd_mode_id: %#10x, cv_mode_id: %#10x, attribute support level: %#10x\n",
>		lwmi_attr_id(...), args.arg0, capdata.supported);
>

I hadn't thought about using that here, good idea.

>> +
>> +	return capdata.supported;
>
>You are casting u32 to int. Return it in a pointer argument if you need
>it.

We don't do anything with the specific value, we just check that the level is above 0. We also don't do anything with the error codes specifically. Perhaps this should return a bool instead and we can return true if this is above 0 and false in all other paths? That would also improve the syntax a bit since the function name is a question and that would allow for !.._is_supported checks.

Thanks,
Derek

>> +}
>> +
>>  /* Lenovo WMI Other Mode Attribute macros */
>>  #define __LWMI_ATTR_RO(_func, _name)                                  \
>>  	{                                                             \
>> @@ -994,12 +1065,13 @@ static int lwmi_om_fw_attr_add(struct lwmi_om_priv *priv)
>>  	}
>>  
>>  	for (i = 0; i < ARRAY_SIZE(cd01_attr_groups) - 1; i++) {
>> +		cd01_attr_groups[i].tunable_attr->dev = &priv->wdev->dev;
>> +		if (lwmi_attr_01_is_supported(cd01_attr_groups[i].tunable_attr)  <= 0)
>
>Extra whitespace.
>
>> +			continue;
>
>Add an empty line in between.
>
>Thanks,
>Rong
>
>>  		err = sysfs_create_group(&priv->fw_attr_kset->kobj,
>>  					 cd01_attr_groups[i].attr_group);
>>  		if (err)
>>  			goto err_remove_groups;
>> -
>> -		cd01_attr_groups[i].tunable_attr->dev = &priv->wdev->dev;
>>  	}
>>  	return 0;
>>