The ACPI specification allows for an EDID to be up to 512 bytes but the _DDC EDID fetching code will only try up to 256 bytes.
Modify the code to instead start at 512 bytes and work it's way down instead. As _DDC is now called up to 4 times on a machine debugging messages are noisier than necessary. Decrease from info to debug. 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 Signed-off-by: Mario Limonciello <mario.limoncie...@amd.com> --- v1->v2: * Use for loop for acpi_video_get_edid() * Use one of Rafael's suggestions for acpi_video_device_EDID() * Decrease message level too I was going to split this separately, but decided to keep it in the same series in case there is any decision to change the interface to acpi_video_get_edid() at the same series. --- drivers/acpi/acpi_video.c | 25 +++++++++---------------- 1 file changed, 9 insertions(+), 16 deletions(-) diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c index 4afdda9db019..3bfd013e09d2 100644 --- a/drivers/acpi/acpi_video.c +++ b/drivers/acpi/acpi_video.c @@ -625,12 +625,9 @@ acpi_video_device_EDID(struct acpi_video_device *device, if (!device) return -ENODEV; - if (length == 128) - arg0.integer.value = 1; - else if (length == 256) - arg0.integer.value = 2; - else + if (!length || (length % 128)) return -EINVAL; + arg0.integer.value = length / 128; status = acpi_evaluate_object(device->dev->handle, "_DDC", &args, &buffer); if (ACPI_FAILURE(status)) @@ -641,7 +638,8 @@ acpi_video_device_EDID(struct acpi_video_device *device, if (obj && obj->type == ACPI_TYPE_BUFFER) *edid = obj; else { - acpi_handle_info(device->dev->handle, "Invalid _DDC data\n"); + acpi_handle_debug(device->dev->handle, + "Invalid _DDC data for length %ld\n", length); status = -EFAULT; kfree(obj); } @@ -1447,7 +1445,6 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, for (i = 0; i < video->attached_count; i++) { video_device = video->attached_array[i].bind_info; - length = 256; if (!video_device) continue; @@ -1478,18 +1475,14 @@ int acpi_video_get_edid(struct acpi_device *device, int type, int device_id, continue; } - status = acpi_video_device_EDID(video_device, &buffer, length); - - if (ACPI_FAILURE(status) || !buffer || - buffer->type != ACPI_TYPE_BUFFER) { - length = 128; + for (length = 512; length > 0; length -= 128) { status = acpi_video_device_EDID(video_device, &buffer, length); - if (ACPI_FAILURE(status) || !buffer || - buffer->type != ACPI_TYPE_BUFFER) { - continue; - } + if (ACPI_SUCCESS(status)) + break; } + if (!length) + continue; *edid = buffer->buffer.pointer; return length; -- 2.34.1
