linux-kernel - Re: mainline build failure due to f1e4c916f97f ("drm/edid: add EDID block count and size helpers")

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Message-ID: <YpT3JlLc7vEfFu8F@shell.armlinux.org.uk>
Date:   Mon, 30 May 2022 17:56:06 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Jani Nikula <jani.nikula@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Shiraz Hashim <shiraz.linux.kernel@...il.com>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        SoC Team <soc@...nel.org>
Subject: Re: mainline build failure due to f1e4c916f97f ("drm/edid: add EDID
 block count and size helpers")

On Mon, May 30, 2022 at 03:35:28PM +0200, Arnd Bergmann wrote:
> The annotations for edid are completely correct and necessary. However
> other driver authors just slap __packed annotations on any structure
> even if the layout is not fixed at all like:
> 
> struct my_driver_priv {
>        struct device dev;
>        u8 causes_misalignment;
>        spinlock_t lock;
>        atomic_t counter;
> } __packed; /* this annotation is harmful because it breaks the atomics */
> 
> or if the annotation does not change the layout like
> 
> struct my_dma_descriptor {
>      __le64 address;
>      __le64 length;
> } __packed; /* does not change layout but makes access slow on some
> architectures */

Sounds like we need a howto document for people to ignore and continue
doing their own thing. :P

-- 
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