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

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Message-ID: <4cef341fdf7a0e877c50b502fc95ee8be28aa811.1743129387.git.soyer@irl.hu>
Date: Fri, 28 Mar 2025 03:44:00 +0100
From: Gergo Koteles <soyer@....hu>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
  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>
Cc: linux-acpi@...r.kernel.org, amd-gfx@...ts.freedesktop.org,
  linux-kernel@...r.kernel.org, Gergo Koteles <soyer@....hu>,
  stable@...r.kernel.org
Subject: [PATCH] ACPI: video: Handle fetching EDID as ACPI_TYPE_PACKAGE

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