Hi,
On 31-Mar-25 1:46 PM, Rafael J. Wysocki wrote:
> On Fri, Mar 28, 2025 at 10:09 PM Gergo Koteles <so...@irl.hu> wrote:
>>
>> 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/
>
> Hans, any concerns here?
No the patch looks good to me:
Reviewed-by: Hans de Goede <hdego...@redhat.com>
Regards,
Hans
>
>> 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
>>
>
