linux-kernel - Re: [PATCH] ACPI: video: Handle fetching EDID as ACPI_TYPE

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Message-ID: <CAJZ5v0hAZ6nYbQ7M5BPbkeMh2_VQFdonBdrFYOfGbq3Y_Kh51w@mail.gmail.com>
Date: Fri, 28 Mar 2025 12:12:17 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Gergo Koteles <soyer@....hu>
Cc: Len Brown <lenb@...nel.org>, Mario Limonciello <mario.limonciello@....com>, 
	Rodrigo Siqueira <siqueira@...lia.com>, Alex Hung <alex.hung@....com>, 
	Alex Deucher <alexander.deucher@....com>, linux-acpi@...r.kernel.org, 
	amd-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	Hans de Goede <hdegoede@...hat.com>
Subject: Re: [PATCH] ACPI: video: Handle fetching EDID as ACPI_TYPE_PACKAGE

CC: Hans

On Fri, Mar 28, 2025 at 3:51 AM Gergo Koteles <soyer@....hu> wrote:
>
> Some Lenovo laptops incorrectly return EDID as
> buffer in ACPI package (instead of just a buffer)
> when calling _DDC.
>
> Calling _DDC generates this ACPI Warning:
> ACPI Warning: \_SB.PCI0.GP17.VGA.LCD._DDC: Return type mismatch - \
> found Package, expected Integer/Buffer (20240827/nspredef-254)
>
> Use the first element of the package to get the EDID buffer.
>
> The DSDT:
>
> Name (AUOP, Package (0x01)
> {
>         Buffer (0x80)
>         {
>         ...
>         }
> })
>
> ...
>
> Method (_DDC, 1, NotSerialized)  // _DDC: Display Data Current
> {
>         If ((PAID == AUID))
>         {
>                 Return (AUOP) /* \_SB_.PCI0.GP17.VGA_.LCD_.AUOP */
>         }
>         ElseIf ((PAID == IVID))
>         {
>                 Return (IVOP) /* \_SB_.PCI0.GP17.VGA_.LCD_.IVOP */
>         }
>         ElseIf ((PAID == BOID))
>         {
>                 Return (BOEP) /* \_SB_.PCI0.GP17.VGA_.LCD_.BOEP */
>         }
>         ElseIf ((PAID == SAID))
>         {
>                 Return (SUNG) /* \_SB_.PCI0.GP17.VGA_.LCD_.SUNG */
>         }
>
>         Return (Zero)
> }
>
> Cc: stable@...r.kernel.org
> Fixes: c6a837088bed ("drm/amd/display: Fetch the EDID from _DDC if available for eDP")
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4085
> Signed-off-by: Gergo Koteles <soyer@....hu>
> ---
>  drivers/acpi/acpi_video.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
> index efdadc74e3f4..65cf36796506 100644
> --- a/drivers/acpi/acpi_video.c
> +++ b/drivers/acpi/acpi_video.c
> @@ -649,6 +649,9 @@ acpi_video_device_EDID(struct acpi_video_device *device, void **edid, int length
>
>         obj = buffer.pointer;
>
> +       if (obj && obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 1)
> +               obj = &obj->package.elements[0];
> +
>         if (obj && obj->type == ACPI_TYPE_BUFFER) {
>                 *edid = kmemdup(obj->buffer.pointer, obj->buffer.length, GFP_KERNEL);
>                 ret = *edid ? obj->buffer.length : -ENOMEM;
> @@ -658,7 +661,7 @@ acpi_video_device_EDID(struct acpi_video_device *device, void **edid, int length
>                 ret = -EFAULT;
>         }
>
> -       kfree(obj);
> +       kfree(buffer.pointer);
>         return ret;
>  }
>
> --
> 2.49.0
>