linux-kernel - Re: [PATCH] drm/edid: Dump the EDID when drm_edid_get_panel

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Message-ID: <CAD=FV=V4m5HNavewSTkrh64_BzLAkivR2mRkTQdaxA8k9JKQbA@mail.gmail.com>
Date:   Mon, 24 Oct 2022 13:28:24 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     dri-devel@...ts.freedesktop.org,
        Kuogee Hsieh <quic_khsieh@...cinc.com>,
        Stephen Boyd <swboyd@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/edid: Dump the EDID when drm_edid_get_panel_id() has
 an error

Hi,

On Fri, Oct 21, 2022 at 2:18 PM Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
>
> Hi Doug
>
> On 10/21/2022 1:07 PM, Douglas Anderson wrote:
> > If we fail to get a valid panel ID in drm_edid_get_panel_id() we'd
> > like to see the EDID that was read so we have a chance of
> > understanding what's wrong. There's already a function for that, so
> > let's call it in the error case.
> >
> > NOTE: edid_block_read() has a retry loop in it, so actually we'll only
> > print the block read back from the final attempt. This still seems
> > better than nothing.
> >
> > Signed-off-by: Douglas Anderson <dianders@...omium.org>
>
> Instead of checkinf for edid_block_status_valid() on the base_block, do
> you want to use drm_edid_block_valid() instead?
>
> That way you get the edid_block_dump() for free if it was invalid.

I can... ...but it feels a bit awkward and maybe not quite how the
functions were intended to work together?

One thing I notice is that if I call drm_edid_block_valid() I'm doing
a bunch of duplicate work that already happened in edid_block_read(),
which already calls edid_block_check() and handles fixing headers. I
guess also if I call drm_edid_block_valid() then I should ignore the
"status" return value of edid_block_read() because we don't need to
pass it anywhere (because the work is re-done in
drm_edid_block_valid()).

So I guess I'm happy to do a v2 like that if everyone likes it better,
but to me it feels a little weird.

-Doug