Re: [Intel-gfx] [PATCH 0/4] drm/amd/display: stop using drm_edid_override_connector_update()

[Alex Hung <alex.hung@amd.com>]

On 2023-08-29 11:03, Jani Nikula wrote:
> On Tue, 29 Aug 2023, Jani Nikula <jani.nikula@intel.com> wrote:
>> On Tue, 29 Aug 2023, Alex Deucher <alexdeucher@gmail.com> wrote:
>>> On Tue, Aug 29, 2023 at 6:48 AM Jani Nikula <jani.nikula@intel.com> wrote:
>>>>
>>>> On Wed, 23 Aug 2023, Jani Nikula <jani.nikula@intel.com> wrote:
>>>>> On Tue, 22 Aug 2023, Alex Hung <alex.hung@amd.com> wrote:
>>>>>> On 2023-08-22 06:01, Jani Nikula wrote:
>>>>>>> Over the past years I've been trying to unify the override and firmware
>>>>>>> EDID handling as well as EDID property updates. It won't work if drivers
>>>>>>> do their own random things.
>>>>>> Let's check how to replace these references by appropriate ones or fork
>>>>>> the function as reverting these patches causes regressions.
>>>>>
>>>>> I think the fundamental problem you have is conflating connector forcing
>>>>> with EDID override. They're orthogonal. The .force callback has no
>>>>> business basing the decisions on connector->edid_override. Force is
>>>>> force, override is override.
>>>>>
>>>>> The driver isn't even supposed to know or care if the EDID originates
>>>>> from the firmware loader or override EDID debugfs. drm_get_edid() will
>>>>> handle that for you transparently. It'll return the EDID, and you
>>>>> shouldn't look at connector->edid_blob_ptr either. Using that will make
>>>>> future work in drm_edid.c harder.
>>>>>
>>>>> You can't fix that with minor tweaks. I think you'll be better off
>>>>> starting from scratch.
>>>>>
>>>>> Also, connector->edid_override is debugfs. You actually can change the
>>>>> behaviour. If your userspace, whatever it is, has been written to assume
>>>>> connector forcing if EDID override is set, you *do* have to fix that,
>>>>> and set both.
>>>>
>>>> Any updates on fixing this, or shall we proceed with the reverts?

There is a patch under internal reviews. It removes calls edid_override 
and drm_edid_override_connector_update as intended in this patchset but 
does not remove the functionality.

With the patch. both following git grep commands return nothing in 
amd-staging-drm-next.

$ git grep drm_edid_override_connector_update -- drivers/gpu/drm/amd
$ git grep edid_override -- drivers/gpu/drm/amd

Best regards,
Alex Hung

>>>
>>> What is the goal of the reverts?  I don't disagree that we may be
>>> using the interfaces wrong, but reverting them will regess
>>> functionality in the driver.
>>
>> The commits are in v6.5-rc1, but not yet in a release. No user depends
>> on them yet. I'd strongly prefer them not reaching v6.5 final and users.
> 
> Sorry for confusion here, that's obviously come and gone already. :(
> 
>> The firmware EDID, override EDID, connector forcing, the EDID property,
>> etc. have been and somewhat still are a hairy mess that we must keep
>> untangling, and this isn't helping.
>>
>> I've put in crazy amounts of work on this, and I've added kernel-doc
>> comments about stuff that should and should not be done, but they go
>> unread and ignored.
>>
>> I really don't want to end up having to clean this up myself before I
>> can embark on further cleanups and refactoring.
>>
>> And again, if the functionality in the driver depends on conflating two
>> things that should be separate, it's probably not such a hot idea to let
>> it reach users either. Even if it's just debugfs.
>>
>>
>> BR,
>> Jani.
>