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: sta...@vger.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 <so...@irl.hu>
---
Changes in v2:
- Added comment
- Improved commit message
- Link to v1:
https://lore.kernel.org/all/4cef341fdf7a0e877c50b502fc95ee8be28aa811.1743129387.git.so...@irl.hu/
drivers/acpi/acpi_video.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index efdadc74e3f4..103f29661576 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -649,6 +649,13 @@ 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;
@@ -658,7 +665,7 @@ 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
