linux-kernel - Re: [PATCH] drm/edid: Fix EDID quirk compile error on older compilers

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Message-ID: <fe48df3f-a6ec-d787-4672-254c8bd4c313@infradead.org>
Date:   Fri, 24 Sep 2021 08:23:54 -0700
From:   Randy Dunlap <rdunlap@...radead.org>
To:     Douglas Anderson <dianders@...omium.org>,
        dri-devel@...ts.freedesktop.org
Cc:     a.hajda@...sung.com, smyakam@...rosoft.com,
        jani.nikula@...ux.intel.com, linus.walleij@...aro.org,
        stanislav.lisovskiy@...el.com, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Jani Nikula <jani.nikula@...el.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thierry Reding <thierry.reding@...il.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/edid: Fix EDID quirk compile error on older compilers

On 9/24/21 7:53 AM, Douglas Anderson wrote:
> Apparently some compilers [1] cannot handle doing math on dereferenced
> string constants at compile time. This has led to reports [2] of
> compile errors like:
> 
>    In file included from drivers/gpu/drm/drm_edid.c:42:0:
>    ./include/drm/drm_edid.h:525:2: error: initializer element is not constant
>      ((((u32)((vend)[0]) - '@') & 0x1f) << 26 | \
> 
> Go back to the syntax I used in v4 of the patch series [3] that added
> this code instead of what landed (v5). This syntax is slightly uglier
> but should be much more compatible with varied compilers.
> 
> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69960#c18
> [2] https://lore.kernel.org/r/874kaabdt5.fsf@intel.com/
> [3] https://lore.kernel.org/r/20210909135838.v4.4.I6103ce2b16e5e5a842b14c7022a034712b434609@changeid/
> 
> Fixes: d9f91a10c3e8 ("drm/edid: Allow querying/working with the panel ID from the EDID")
> Reported-by: Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>
> Reported-by: Srikanth Myakam <smyakam@...rosoft.com>
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> ---
> 
>   drivers/gpu/drm/drm_edid.c        | 121 +++++++++++++++---------------
>   drivers/gpu/drm/panel/panel-edp.c |  23 +++---
>   include/drm/drm_edid.h            |  14 ++--
>   3 files changed, 81 insertions(+), 77 deletions(-)
> 

Works for me. Thanks.

Acked-by: Randy Dunlap <rdunlap@...radead.org> # build-tested


-- 
~Randy