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

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Date:   Mon, 14 Nov 2022 12:02:28 +0200
From:   Jani Nikula <jani.nikula@...ux.intel.com>
To:     Doug Anderson <dianders@...omium.org>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>
Cc:     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

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.

BR,
Jani.

>
> Thanks!
>
> -Doug

-- 
Jani Nikula, Intel Open Source Graphics Center