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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Sat, 28 May 2022 13:31:24 -0700
Message-ID: <CAHk-=whfmwzjF4eBPYS6pHFqHVzJF3m=2h=gRWSRyHks8V=ABA@mail.gmail.com>
Subject: Re: mainline build failure due to f1e4c916f97f ("drm/edid: add EDID
 block count and size helpers")
To:     Arnd Bergmann <arnd@arndb.de>
Cc:     Sudip Mukherjee <sudipm.mukherjee@gmail.com>,
        Russell King <linux@armlinux.org.uk>,
        Viresh Kumar <vireshk@kernel.org>,
        Shiraz Hashim <shiraz.linux.kernel@gmail.com>,
        Jani Nikula <jani.nikula@intel.com>,
        =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= <ville.syrjala@linux.intel.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        SoC Team <soc@kernel.org>
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On Sat, May 28, 2022 at 11:59 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> It's CONFIG_ARM_AEABI, which is normally set everywhere. Without this
> option, you the kernel is built for the old 'OABI' that forces all non-packed
> struct members to be at least 16-bit aligned.

Looks like forced word (32 bit) alignment to me.

I wonder how many other structures that messes up, but I committed the
EDID fix for now.

This has presumably been broken for a long time, but maybe the
affected targets don't typically use EDID and kernel modesetting, and
only use some fixed display setup instead.

Those structure definitions go back a _loong_ time (from a quick 'git
blame' I see November 2008).

But despite that, I did not mark my fix 'cc:stable' because I don't
know if any of those machines affected by this bad arm ABI issue could
possibly care.

At least my tree hopefully now builds on them, with the BUILD_BUG_ON()
that uncovered this.

                   Linus