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

[Jani Nikula <jani.nikula@intel.com>]

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?
>
> 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.

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.


-- 
Jani Nikula, Intel Open Source Graphics Center