linux-kernel - Re: [PATCH] drm/bochs: add edid present check

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Message-ID: <4a1897bf-2b48-fdd7-25e3-d7d25b9885c3@gmail.com>
Date:   Wed, 19 Dec 2018 17:37:10 +0200
From:   Oleksandr Andrushchenko <andr2000@...il.com>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR BOCHS VIRTUAL GPU" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH] drm/bochs: add edid present check

On 12/19/18 5:21 PM, Gerd Hoffmann wrote:
>    Hi,
>
>> You could probably have a comment here explaining the magic below
>> (just like in the commit message to ease the task of understanding
>> while reading the code why 2 of 8 bytes of the EDID header is checked
>> and why it is all needed). Of course one can use git blame... Up to you
> Makes sense.
>
>>> +	if (readb(bochs->mmio + 0) != 0x00 ||
>>> +	    readb(bochs->mmio + 1) != 0xff)
>> bochs->mmio is defined as "void __iomem   *mmio;". Can we please avoid
>> void pointer arithmetic here?
> Why is that a problem?  gcc uses bytes when doing pointer arithmetic
> with void pointers (even though it is undefined in the C standard),
> and as far I know the linux kernel depends on that behavior anyway.
>
> Also the driver already does it everywhere.
Ok then, just to be consistent with the rest of the driver.
> cheers,
>    Gerd
>