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

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Message-ID: <CAD=FV=WPa+CayKowHBDTRZTgv9FtCZWUWiKv-UB7XmQ4D+9P7w@mail.gmail.com>
Date:   Mon, 14 Nov 2022 14:08:30 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Jani Nikula <jani.nikula@...ux.intel.com>
Cc:     Abhinav Kumar <quic_abhinavk@...cinc.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Stephen Boyd <swboyd@...omium.org>,
        Kuogee Hsieh <quic_khsieh@...cinc.com>
Subject: Re: [PATCH] drm/edid: Dump the EDID when drm_edid_get_panel_id() has
 an error

Hi,

On Mon, Nov 14, 2022 at 2:02 AM Jani Nikula <jani.nikula@...ux.intel.com> wrote:
>
> On Fri, 11 Nov 2022, Doug Anderson <dianders@...omium.org> wrote:
> > Hi,
> >
> > On Tue, Oct 25, 2022 at 1:39 PM Abhinav Kumar <quic_abhinavk@...cinc.com> wrote:
> >>
> >> Hi Doug
> >>
> >> On 10/24/2022 1:28 PM, Doug Anderson wrote:
> >> > 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
> >>
> >> Alright, agreed. There is some duplication of code happening if we use
> >> drm_edid_block_valid(). I had suggested that because it has inherent
> >> support for dumping the bad EDID.
> >>
> >> In that case, this change LGTM, because in principle you are doing the
> >> same thing as _drm_do_get_edid() (with the only difference being here we
> >> read only the base block as opposed to the full EDID there).
> >>
> >> Hence,
> >>
> >> Reviewed-by: Abhinav Kumar <quic_abhinavk@...cinc.com>
> >
> > I've given this patch a bunch of time because it wasn't urgent, but
> > seems like it could be about time to land. I'll plan to land it next
> > Monday or Tuesday unless anyone has any other comments.
>
> Ack, it's benign enough.

Thanks! Since you didn't write the above as an Acked-by tag I didn't
add it to the commit, but I went ahead and landed with Abhinav's tag.

69c7717c20cc drm/edid: Dump the EDID when drm_edid_get_panel_id() has an error

-Doug