Re: [PATCH 1/2] drm_edid: Add a function to get EDID base block

Jani Nikula
2024-03-04T20:44:20Z

On Mon, 04 Mar 2024, Hsin-Yi Wang <hsinyi@chromium.org> wrote:
> On Mon, Mar 4, 2024 at 8:17 AM Doug Anderson <dianders@chromium.org> wrote:
>>
>> Hi,
>>
>> On Sun, Mar 3, 2024 at 1:30 PM Dmitry Baryshkov
>> <dmitry.baryshkov@linaro.org> wrote:
>> >
>> > > The problem is that Dmitry didn't like the idea of using a hash and in
>> > > v2 Hsin-Yi has moved to using the name of the display. ...except of
>> > > course that eDP panels don't always properly specify
>> > > "EDID_DETAIL_MONITOR_NAME". See the discussion [1]. If you want to see
>> > > some of the EDIDs involved, you can see Hsin-Yi's post [2]. The panels
>> > > included stuff like this:
>> > >
>> > > Alphanumeric Data String: 'AUO'
>> > > Alphanumeric Data String: 'B116XAN04.0 '
>> > >
>> > > The fact that there is more than one string in there makes it hard to
>> > > just "return" the display name in a generic way. The way Hsin-Yi's
>> > > code was doing it was that it would consider it a match if the panel
>> > > name was in any of the strings...
>> > >
>> > > How about this as a solution: we change drm_edid_get_panel_id() to
>> > > return an opaque type (struct drm_edid_panel_id_blob) that's really
>> > > just the first block of the EDID but we can all pretend that it isn't.
>> > > Then we can add a function in drm_edid.c that takes this opaque blob,
>> > > a 32-bit integer (as per drm_edid_encode_panel_id()), and a string
>> > > name and it can tell us if the blob matches?
>> >
>> > Would it be easier to push drm_edid_match to drm_edid.c? It looks way
>> > more simpler than the opaque blob.
>>
>> Yeah, that sounds reasonable / cleaner to me. Good idea! Maybe Hsin-Yi
>> will be able to try this out and see if there's a reason it wouldn't
>> work.
>
> Thanks for all the suggestions. I sent out v3, which still has a blob
> type since we need
> 1. get panel id
> 2. do the string matching.
>
> And I felt that packing these 2 steps into one function may make that
> function do multiple tasks?
>
> But let me know if it's preferred in this way.
>
> v3: https://lore.kernel.org/lkml/20240304195214.14563-1-hsinyi@chromium.org/

I still don't like it, but incorporating all the ideas here, and in the
previous patches, I think I have a suggestion that covers all cases in a
reasonable manner [1].

Sorry about being so inflexible about this. I've just put 140+ commits
worth of effort in drm_edid.c in the past couple of years, and I'm keen
on keeping it nice and tidy. :)

BR,
Jani.

[1] https://lore.kernel.org/r/87a5nd4tsg.fsf@intel.com

>
>>
>> -Doug

--
Jani Nikula, Intel