linux-kernel - Re: [PATCH] drm: fourcc byteorder: brings header file comments in line with reality.

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Message-ID: <20170421094449.GF30290@intel.com>
Date:   Fri, 21 Apr 2017 12:44:49 +0300
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     Pekka Paalanen <ppaalanen@...il.com>,
        dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        Ilia Mirkin <imirkin@...m.mit.edu>,
        Michel Dänzer <michel@...nzer.net>,
        Alex Deucher <alexdeucher@...il.com>,
        amd-gfx@...ts.freedesktop.org,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Sean Paul <seanpaul@...omium.org>,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm: fourcc byteorder: brings header file comments in
 line with reality.

On Fri, Apr 21, 2017 at 11:38:28AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > > Leaving the yuv formats as-is.  I have no idea if and how those are used
> > > on bigendian machines.
> 
> > just an idea - since we are not sure how the remaining formats are being
> > used, should those be marked somehow uncertain whether they are little
> > or native endian?
> 
> ATM the yuv don't have any byte order annotations, and I simply left
> them that way.  So it is as clear/unclear as before.

Eh? Everything that is affected by byte order has the relevant comments.
If they don't, then that's a bug.

> 
> IIRC someone mentioned that for the yuv fourccs there actually is some
> standard about the exact ordering.  Anyone has a good reference?  We
> could stick a link to it into a comment.

The "standard" is fourcc. Whether there is any official reference for
that is unclear. That's exactly why I added the explicit comments into
drm_fourcc.h so that people don't have to go trawling the internets
looking for information on what each pixel format might mean.

-- 
Ville Syrjälä
Intel OTC