linux-kernel - Re: [PATCH v3 2/4] drm/edid: Add a function to check monitor string

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Message-ID: <CAJMQK-hE8sWL2rO-N2WZuyXzPhnXZJN4LUL_TwzKGhq_Ozz6Vw@mail.gmail.com>
Date: Tue, 5 Mar 2024 16:48:12 -0800
From: Hsin-Yi Wang <hsinyi@...omium.org>
To: Doug Anderson <dianders@...omium.org>
Cc: Jani Nikula <jani.nikula@...ux.intel.com>, 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, 
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Subject: Re: [PATCH v3 2/4] drm/edid: Add a function to check monitor string

On Tue, Mar 5, 2024 at 11:25 AM Doug Anderson <dianders@...omium.org> wrote:
>
> Hi,
>
> On Tue, Mar 5, 2024 at 12:17 AM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
> >
> > On Mon, 04 Mar 2024, Doug Anderson <dianders@...omium.org> wrote:
> > > Hi,
> > >
> > > On Mon, Mar 4, 2024 at 4:19 PM Hsin-Yi Wang <hsinyi@...omium.org> wrote:
> > >>
> > >> > > Probably change to u32 drm_edid_get_panel_id(const struct drm_edid
> > >> > > *);? Given that we still need to parse id from
> > >> > > drm_edid_read_base_block().
> > >> >
> > >> > No, we no longer need to parse the id outside of drm_edid.c. You'll have
> > >> > the id's in panel code in the form of struct drm_edid_ident (or
> > >> > whatever), and use the match function to see if the opaque drm_edid
> > >> > matches.
> > >> >
> > >> drm_panel prints the panel_id info on whether the panel is detected or not.
> > >> https://elixir.bootlin.com/linux/v6.8-rc7/source/drivers/gpu/drm/panel/panel-edp.c#L792
> > >>
> > >> Is it okay to remove this information?
> > >
> > > Hmmm, I guess it also is exported via debugfs, actually. See
> > > detected_panel_show() in panel-edp.c. We probably don't want to remove
> > > that...
> >
> > You currently print the information via panel->detected_panel, which is
> > a struct edp_panel_entry *. That doesn't change. It'll be slightly
> > restructured to contain a struct drm_edid_ident, which will not be an
> > opaque type.
>
> Hmm. As Hsin-Yi pointed out to me offline. Somehow we'll need to get
> the actual panel ID out. Right now in panel-edp.c we have:
>
> dev_warn(dev,
>   "Unknown panel %s %#06x, using conservative timings\n",
>   vend, product_id);
>
> Where "vend" and "product_id" come from the panel ID of a panel that
> we didn't recognize. For instance:
>
>   Unknown panel BOE 0x0731, using conservative timings
>
> We need to still be able to print this message for unrecognized
> panels. Then when we see field reports including this message we know
> that somehow we ended up shipping an unrecognized panel.
>
> Any suggestions on what abstraction you'd like to see to enable us to
> print that message if everything is opaque?

Sent v4 here: https://lore.kernel.org/lkml/20240306004347.974304-1-hsinyi@chromium.org/

Besides that it still keeps drm_edid_get_panel_id() to be used on the
kernel warning when no panel is matched, other parts I think are
following the comments.

Thanks.
>
> -Doug