ACPI: video: Handle fetching EDID as ACPI_TYPE_PACKAGE

JIRA: https://issues.redhat.com/browse/RHEL-114091

commit ebca08f
Author: Gergo Koteles <soyer@irl.hu>
Date: Mon, 31 Mar 2025 17:02:14 +0000

The _DDC method should return a buffer, or an integer in case of an error.
But some Lenovo laptops incorrectly return EDID as buffer in ACPI package.

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)
}

Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/Apx_B_Video_Extensions/output-device-specific-methods.html#ddc-return-the-edid-for-this-device
Cc: stable@vger.kernel.org
Fixes: c6a8370 ("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@irl.hu>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
Link: https://patch.msgid.link/61c3df83ab73aba0bc7a941a443cd7faf4cf7fb0.1743195250.git.soyer@irl.hu
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Mark Langsdorf <mlangsdo@redhat.com>

Author: mlangsdorf

drivers/acpi/acpi_video.c

@@ -710,6 +710,13 @@ acpi_video_device_EDID(struct acpi_video_device *device, void **edid, int length
 
 	obj = buffer.pointer;
 
+	/*
+	 * Some buggy implementations incorrectly return the EDID buffer in an ACPI package.
+	 * In this case, extract the buffer from the package.
+	 */
+	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;
@@ -719,7 +726,7 @@ acpi_video_device_EDID(struct acpi_video_device *device, void **edid, int length
 		ret = -EFAULT;
 	}
 
-	kfree(obj);
+	kfree(buffer.pointer);
 	return ret;
 }