linux-kernel - Re: [PATCH v11 1/7] platform/x86: lenovo-wmi-helpers: Convert returned buffer into u32

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Message-Id: <94a3798f-c6da-4b26-b082-d1b56d059019@app.fastmail.com>
Date: Thu, 22 Jan 2026 13:51:25 -0500
From: "Mark Pearson" <mpearson-lenovo@...ebb.ca>
To: "Rong Zhang" <i@...g.moe>, "Derek J . Clark" <derekjohn.clark@...il.com>,
 "Armin Wolf" <W_Armin@....de>, "Hans de Goede" <hansg@...nel.org>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc: "Guenter Roeck" <linux@...ck-us.net>, "Kurt Borja" <kuurtb@...il.com>,
 "platform-driver-x86@...r.kernel.org" <platform-driver-x86@...r.kernel.org>,
 linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v11 1/7] platform/x86: lenovo-wmi-helpers: Convert returned buffer
 into u32

On Tue, Jan 20, 2026, at 1:20 PM, Rong Zhang wrote:
> The Windows WMI-ACPI driver converts all ACPI objects into a common
> buffer format, so returning a buffer with four bytes will look like an
> integer for WMI consumers under Windows.
>
> Therefore, some devices may simply implement the corresponding ACPI
> methods to always return a buffer. While lwmi_dev_evaluate_int() expects
> an integer (u32), convert returned >=4B buffer into u32 to support these
> devices.
>
> Suggested-by: Armin Wolf <W_Armin@....de>
> Link: https://lore.kernel.org/r/f1787927-b655-4321-b9d9-bc12353c72db@gmx.de/
> Signed-off-by: Rong Zhang <i@...g.moe>
> Reviewed-by: Derek J. Clark <derekjohn.clark@...il.com>
> Tested-by: Derek J. Clark <derekjohn.clark@...il.com>
> Reviewed-by: Armin Wolf <W_Armin@....de>
> ---
> Changes in v7:
> - Fix mistakenly inverted boundary check
>
> Changes in v4:
> - Accept oversized buffer (thanks Armin Wolf)
> - Use get_unaligned_le32() (ditto)
>
> Changes in v2:
> - New patch (thanks Armin Wolf)
> ---
>  drivers/platform/x86/lenovo/wmi-helpers.c | 21 ++++++++++++++++++---
>  1 file changed, 18 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/platform/x86/lenovo/wmi-helpers.c 
> b/drivers/platform/x86/lenovo/wmi-helpers.c
> index f6fef6296251e..7379defac5002 100644
> --- a/drivers/platform/x86/lenovo/wmi-helpers.c
> +++ b/drivers/platform/x86/lenovo/wmi-helpers.c
> @@ -21,6 +21,7 @@
>  #include <linux/errno.h>
>  #include <linux/export.h>
>  #include <linux/module.h>
> +#include <linux/unaligned.h>
>  #include <linux/wmi.h>
> 
>  #include "wmi-helpers.h"
> @@ -59,10 +60,24 @@ int lwmi_dev_evaluate_int(struct wmi_device *wdev, 
> u8 instance, u32 method_id,
>  		if (!ret_obj)
>  			return -ENODATA;
> 
> -		if (ret_obj->type != ACPI_TYPE_INTEGER)
> -			return -ENXIO;
> +		switch (ret_obj->type) {
> +		/*
> +		 * The ACPI method may simply return a buffer when a u32
> +		 * is expected. This is valid on Windows as its WMI-ACPI
> +		 * driver converts everything to a common buffer.
> +		 */
> +		case ACPI_TYPE_BUFFER:
> +			if (ret_obj->buffer.length < sizeof(u32))
> +				return -ENXIO;
> 
> -		*retval = (u32)ret_obj->integer.value;
> +			*retval = get_unaligned_le32(ret_obj->buffer.pointer);
> +			return 0;
> +		case ACPI_TYPE_INTEGER:
> +			*retval = (u32)ret_obj->integer.value;
> +			return 0;
> +		default:
> +			return -ENXIO;
> +		}
>  	}
> 
>  	return 0;
> -- 
> 2.51.0

Looks good to me.

As an aside, you've answered a question that was puzzling me for something we're working on internally as to why the Windows dev team hadn't complained about different formats between platforms for their implementations (which was causing me a ton of pain). Now it all makes sense!

Reviewed-by: Mark Pearson <mpearson-lenovo@...ebb.ca>