Re: [PATCH 1/2] platform/x86: wmi: Fix WMI event enablement

[Ilpo Järvinen]

On Fri, 20 Jun 2025, Armin Wolf wrote:

> It turns out that the Windows WMI-ACPI driver always enables/disables
> WMI events regardless of whether they are marked as expensive or not.
> This finding is further reinforced when reading the documentation of
> the WMI_FUNCTION_CONTROL_CALLBACK callback used by Windows drivers
> for enabling/disabling WMI devices:
> 
> 	The DpWmiFunctionControl routine enables or disables
> 	notification of events, and enables or disables data
> 	collection for data blocks that the driver registered
> 	as expensive to collect.
> 
> Follow this behavior to fix the WMI event used for reporting hotkey
> events on the Dell Latitude 5400 and likely many more devices.
> 
> Reported-by: Dmytro Bagrii <dimich.dmb@xxxxxxxxx>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=220246
> Tested-by: Dmytro Bagrii <dimich.dmb@xxxxxxxxx>
> Fixes: 656f0961d126 ("platform/x86: wmi: Rework WCxx/WExx ACPI method handling")
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
>  drivers/platform/x86/wmi.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 21b7e54bd7ab..4e86a422f05f 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -180,16 +180,22 @@ static int wmi_device_enable(struct wmi_device *wdev, bool enable)
>  	acpi_handle handle;
>  	acpi_status status;
>  
> -	if (!(wblock->gblock.flags & ACPI_WMI_EXPENSIVE))
> -		return 0;
> -
>  	if (wblock->dev.dev.type == &wmi_type_method)
>  		return 0;
>  
> -	if (wblock->dev.dev.type == &wmi_type_event)
> +	if (wblock->dev.dev.type == &wmi_type_event) {
> +		/*
> +		 * Windows always enables/disables WMI events, even when they are
> +		 * not marked as being expensive. We follow this behavior for

Hi Armin,

Is the wording in the comment reversed? (I suspect you didn't mean to 
include "not" into that statement?)

> +		 * compatibility reasons.
> +		 */
>  		snprintf(method, sizeof(method), "WE%02X", wblock->gblock.notify_id);
> -	else
> +	} else {
> +		if (!(wblock->gblock.flags & ACPI_WMI_EXPENSIVE))
> +			return 0;
> +
>  		get_acpi_method_name(wblock, 'C', method);
> +	}
>  
>  	/*
>  	 * Not all WMI devices marked as expensive actually implement the
> 

-- 
 i.