From 5d389afc1f8fea707225bc2ee64e00d85dab623a Mon Sep 17 00:00:00 2001
From: Mario Limonciello <mario.limonciello@amd.com>
Date: Thu, 1 Feb 2024 16:11:15 -0600
Subject: [PATCH] ACPI: video: Handle fetching EDID that is longer than 256
bytes
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.limonciello@amd.com>
[ rjw: Type mismatch fix, minor whitespace adjustment ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/acpi/acpi_video.c | 28 +++++++++++-----------------
1 file changed, 11 insertions(+), 17 deletions(-)
diff --git a/drivers/acpi/acpi_video.c b/drivers/acpi/acpi_video.c
index 4afdda9db0195..1fda303882973 100644
--- a/drivers/acpi/acpi_video.c
+++ b/drivers/acpi/acpi_video.c
@@ -612,7 +612,7 @@ acpi_video_device_lcd_get_level_current(struct acpi_video_device *device,
static int
acpi_video_device_EDID(struct acpi_video_device *device,
- union acpi_object **edid, ssize_t length)
+ union acpi_object **edid, int length)
{
int status;
struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
@@ -625,13 +625,11 @@ 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))
return -ENODEV;
@@ -641,7 +639,8 @@ 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 %d\n", length);
status = -EFAULT;
kfree(obj);
}
@@ -1447,7 +1446,6 @@ 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 +1476,14 @@ 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;