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 <[email protected]>
---
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
---
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
On Thu, Feb 1, 2024 at 11:11 PM Mario Limonciello
<[email protected]> wrote:
>
> 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 <[email protected]>
Acked-by: Rafael J. Wysocki <[email protected]>
or I can apply it if that's preferred.
Thanks!
> ---
> 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
> ---
> 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
>
On 2/2/2024 10:07, Rafael J. Wysocki wrote:
> On Thu, Feb 1, 2024 at 11:11 PM Mario Limonciello
> <[email protected]> wrote:
>>
>> 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 <[email protected]>
>
> Acked-by: Rafael J. Wysocki <[email protected]>
>
> or I can apply it if that's preferred.
Thanks!
I think go ahead and apply this one to your -next tree.
The rest might take a few weeks to get right and no need to block on this.
>
> Thanks!
>
>> ---
>> 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
>> ---
>> 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
>>
On Fri, Feb 2, 2024 at 5:09 PM Mario Limonciello
<[email protected]> wrote:
>
> On 2/2/2024 10:07, Rafael J. Wysocki wrote:
> > On Thu, Feb 1, 2024 at 11:11 PM Mario Limonciello
> > <[email protected]> wrote:
> >>
> >> 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 <[email protected]>
> >
> > Acked-by: Rafael J. Wysocki <[email protected]>
> >
> > or I can apply it if that's preferred.
>
> Thanks!
>
> I think go ahead and apply this one to your -next tree.
Applied now.
Barring any issues with it, It will get into linux-next in a couple of days.
Thanks!