linux-kernel - Re: [PATCH v2 1/6] platform/x86: lenovo-wmi-helpers: convert returned 4B buffer into u32

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Message-ID: <CAFqHKTn4tEqGpTpyaWEMUHvskRux1RHGxp89tWr1UeYgsnsV2Q@mail.gmail.com>
Date: Thu, 30 Oct 2025 18:56:42 -0700
From: Derek John Clark <derekjohn.clark@...il.com>
To: Rong Zhang <i@...g.moe>
Cc: Mark Pearson <mpearson-lenovo@...ebb.ca>, Armin Wolf <W_Armin@....de>, 
	Hans de Goede <hansg@...nel.org>, Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>, 
	Guenter Roeck <linux@...ck-us.net>, platform-driver-x86@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-hwmon@...r.kernel.org
Subject: Re: [PATCH v2 1/6] platform/x86: lenovo-wmi-helpers: convert returned
 4B buffer into u32

On Thu, Oct 30, 2025 at 12:40 PM Rong Zhang <i@...g.moe> 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 4-byte 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>
> ---
> 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..f3bc92ac505ac 100644
> --- a/drivers/platform/x86/lenovo/wmi-helpers.c
> +++ b/drivers/platform/x86/lenovo/wmi-helpers.c
> @@ -59,10 +59,25 @@ 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 4-byte buffer when a u32
> +                * integer 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 != 4)
> +                               return -ENXIO;
>
> -               *retval = (u32)ret_obj->integer.value;
> +                       *retval = *((u32 *)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
>

Reviewed-by: Derek J. Clark <derekjohn.clark@...il.com>

Thanks,
Derek