Re: [PATCH v2] platform/x86: asus-wmi: add keystone dongle support

["Dariusz Figzał" <dariuszfigzal@gmail.com>]

On 6/10/26 2:25 PM, Ilpo Järvinen wrote:
> On Thu, 28 May 2026, Dariusz Figzał wrote:
> 
>> The ASUS Keystone is a physical NFC-like dongle that slots into supported
>> ASUS laptops. The EC fires WMI notify code 0xB4 on insert/remove events.
>>
>> Expose the current insert state via a sysfs attribute by querying WMI
>> device ID 0x00120091 (DSTS). This devid does not follow the standard DSTS
>> convention: PRESENCE_BIT (0x00010000) encodes the insert state rather than
>> feature presence, and STATUS_BIT is never set. Presence of a keystone slot
>> is detected by a successful DSTS call.
>>
>> Signed-off-by: Dariusz Figzał <dariuszfigzal@gmail.com>
>> ---
>>
>> Changes in v2:
>> - Use .is_visible and platform_attributes[] instead of
>>    device_create_file/device_remove_file (Ilpo Järvinen)
>>
>>   drivers/platform/x86/asus-wmi.c            | 65 ++++++++++++++++++++++
>>   include/linux/platform_data/x86/asus-wmi.h |  7 +++
> 
> Please document the interface in
> Documentation/ABI/testing/sysfs-platform-asus-wmi
> 
> --
>   i.

I'll add the documentation in v3. Thanks for the review.

> 
>>   2 files changed, 72 insertions(+)
>>
>> diff --git a/drivers/platform/x86/asus-wmi.c b/drivers/platform/x86/asus-wmi.c
>> index 80144c412b90..3c9ef826551d 100644
>> --- a/drivers/platform/x86/asus-wmi.c
>> +++ b/drivers/platform/x86/asus-wmi.c
>> @@ -70,6 +70,7 @@ module_param(fnlock_default, bool, 0444);
>>   #define NOTIFY_KBD_TTP			0xae
>>   #define NOTIFY_LID_FLIP			0xfa
>>   #define NOTIFY_LID_FLIP_ROG		0xbd
>> +#define NOTIFY_KEYSTONE			0xb4
>>   
>>   #define ASUS_WMI_FNLOCK_BIOS_DISABLED	BIT(0)
>>   
>> @@ -279,6 +280,8 @@ struct asus_wmi {
>>   	u32 tablet_switch_dev_id;
>>   	bool tablet_switch_inverted;
>>   
>> +	bool keystone_available;
>> +
>>   	enum fan_type fan_type;
>>   	enum fan_type gpu_fan_type;
>>   	enum fan_type mid_fan_type;
>> @@ -646,6 +649,55 @@ static bool asus_wmi_dev_is_present(struct asus_wmi *asus, u32 dev_id)
>>   	return status == 0 && (retval & ASUS_WMI_DSTS_PRESENCE_BIT);
>>   }
>>   
>> +/* Keystone *******************************************************************/
>> +
>> +static int keystone_check_present(struct asus_wmi *asus)
>> +{
>> +	u32 retval;
>> +	int err;
>> +
>> +	asus->keystone_available = false;
>> +
>> +	/*
>> +	 * Use a raw devstate call rather than asus_wmi_dev_is_present().
>> +	 * For this devid, PRESENCE_BIT encodes current insert state, not
>> +	 * feature presence, so asus_wmi_dev_is_present() would return false
>> +	 * whenever the dongle is absent at boot, even on machines that have
>> +	 * a keystone slot.
>> +	 * -ENODEV means the firmware doesn't know this devid at all.
>> +	 * retval is not examined here, only the return code matters.
>> +	 */
>> +	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_KEYSTONE, &retval);
>> +	if (err == -ENODEV)
>> +		return 0;
>> +	if (err)
>> +		return err;
>> +
>> +	asus->keystone_available = true;
>> +	return 0;
>> +}
>> +
>> +static ssize_t keystone_show(struct device *dev,
>> +			     struct device_attribute *attr, char *buf)
>> +{
>> +	struct asus_wmi *asus = dev_get_drvdata(dev);
>> +	u32 retval;
>> +	int err;
>> +
>> +	err = asus_wmi_get_devstate(asus, ASUS_WMI_DEVID_KEYSTONE, &retval);
>> +	if (err)
>> +		return err;
>> +
>> +	return sysfs_emit(buf, "%d\n", !!(retval & ASUS_WMI_DSTS_PRESENCE_BIT));
>> +}
>> +
>> +static DEVICE_ATTR_RO(keystone);
>> +
>> +static void asus_wmi_keystone_notify(struct asus_wmi *asus)
>> +{
>> +	sysfs_notify(&asus->platform_device->dev.kobj, NULL, "keystone");
>> +}
>> +
>>   /* Input **********************************************************************/
>>   static void asus_wmi_tablet_sw_report(struct asus_wmi *asus, bool value)
>>   {
>> @@ -4575,6 +4627,12 @@ static void asus_wmi_handle_event_code(int code, struct asus_wmi *asus)
>>   		return;
>>   	}
>>   
>> +	if (code == NOTIFY_KEYSTONE) {
>> +		if (asus->keystone_available)
>> +			asus_wmi_keystone_notify(asus);
>> +		return;
>> +	}
>> +
>>   	if (code == NOTIFY_KBD_FBM || code == NOTIFY_KBD_TTP) {
>>   		if (asus->fan_boost_mode_available)
>>   			fan_boost_mode_switch_next(asus);
>> @@ -4698,6 +4756,7 @@ static struct attribute *platform_attributes[] = {
>>   	&dev_attr_lid_resume.attr,
>>   	&dev_attr_als_enable.attr,
>>   	&dev_attr_fan_boost_mode.attr,
>> +	&dev_attr_keystone.attr,
>>   #if IS_ENABLED(CONFIG_ASUS_WMI_DEPRECATED_ATTRS)
>>   		&dev_attr_charge_mode.attr,
>>   		&dev_attr_egpu_enable.attr,
>> @@ -4741,6 +4800,8 @@ static umode_t asus_sysfs_is_visible(struct kobject *kobj,
>>   		devid = ASUS_WMI_DEVID_ALS_ENABLE;
>>   	else if (attr == &dev_attr_fan_boost_mode.attr)
>>   		ok = asus->fan_boost_mode_available;
>> +	else if (attr == &dev_attr_keystone.attr)
>> +		ok = asus->keystone_available;
>>   
>>   #if IS_ENABLED(CONFIG_ASUS_WMI_DEPRECATED_ATTRS)
>>   	if (attr == &dev_attr_charge_mode.attr)
>> @@ -5081,6 +5142,10 @@ static int asus_wmi_add(struct platform_device *pdev)
>>   	if (err)
>>   		goto fail_platform_profile_setup;
>>   
>> +	err = keystone_check_present(asus);
>> +	if (err)
>> +		dev_warn(&pdev->dev, "Failed to check Keystone presence: %d\n", err);
>> +
>>   	err = asus_wmi_sysfs_init(asus->platform_device);
>>   	if (err)
>>   		goto fail_sysfs;
>> diff --git a/include/linux/platform_data/x86/asus-wmi.h b/include/linux/platform_data/x86/asus-wmi.h
>> index 554f41b827e1..c29962d5baac 100644
>> --- a/include/linux/platform_data/x86/asus-wmi.h
>> +++ b/include/linux/platform_data/x86/asus-wmi.h
>> @@ -147,6 +147,13 @@
>>   #define ASUS_WMI_DEVID_GPU_MUX		0x00090016
>>   #define ASUS_WMI_DEVID_GPU_MUX_VIVO	0x00090026
>>   
>> +/* Keystone dongle insert/remove state.
>> + * PRESENCE_BIT (0x00010000) encodes insert state:
>> + * 0x00010000 = inserted, 0x00000000 = absent. STATUS_BIT is never set.
>> + * 0xFFFFFFFE means no keystone slot on this machine.
>> + */
>> +#define ASUS_WMI_DEVID_KEYSTONE		0x00120091
>> +
>>   /* TUF laptop RGB modes/colours */
>>   #define ASUS_WMI_DEVID_TUF_RGB_MODE	0x00100056
>>   #define ASUS_WMI_DEVID_TUF_RGB_MODE2	0x0010005A