linux-kernel - Re: [PATCH 0/2] Match panel hash for overridden mode

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Message-ID: <CAD=FV=WjZZfHBdMVG3R_iT9bskP3AyHrRsSK6Hfw9h4tEZBHFg@mail.gmail.com>
Date: Mon, 26 Feb 2024 17:00:08 -0800
From: Doug Anderson <dianders@...omium.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Hsin-Yi Wang <hsinyi@...omium.org>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Jessica Zhang <quic_jesszhan@...cinc.com>, Sam Ravnborg <sam@...nborg.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] Match panel hash for overridden mode

Hi,

On Mon, Feb 26, 2024 at 4:37 PM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On Sat, 24 Feb 2024 at 00:40, Hsin-Yi Wang <hsinyi@...omium.org> wrote:
> >
> > This series is a follow up for 1a5e81de180e ("Revert "drm/panel-edp: Add
> > auo_b116xa3_mode""). It's found that 2 different AUO panels use the same
> > product id. One of them requires an overridden mode, while the other should
> > use the mode directly from edid.
> >
> > Since product id match is no longer sufficient, EDP_PANEL_ENTRY2 is extended
> > to check the crc hash of the entire edid base block.
>
> Do you have these EDIDs posted somewhere? Can we use something less
> cryptic than hash for matching the panel, e.g. strings from Monitor
> Descriptors?

We could try it if need be. I guess I'm worried that if panel vendors
ended up re-using the panel ID for two different panels that they
might also re-use the name field too. Hashing the majority of the
descriptor's base block makes us more likely not to mix two panels up.
In general it feels like the goal is that if there is any doubt that
we shouldn't override the mode and including more fields in the hash
works towards that goal.

I guess one thing that might help would be to make it a policy that
any time a panel is added to this list that a full EDID is included in
the commit message. That would mean that if we ever needed to change
things we could. What do you think?

That being said, if everyone thinks that the "name" field is enough,
we could do it. I think that in the one case that we ran into it would
have been enough...

-Doug