linux-kernel - Re: [EXT] Re: [PATCH v5 07/10] media: Add parsing for APP14 data segment in jpeg helpers

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Message-ID: <ebaf3126dddf686e1ff07e00c61cd43c07ab07cd.camel@pengutronix.de>
Date:   Fri, 04 Dec 2020 15:32:34 +0100
From:   Philipp Zabel <p.zabel@...gutronix.de>
To:     "Mirela Rabulea (OSS)" <mirela.rabulea@....nxp.com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "hverkuil-cisco@...all.nl" <hverkuil-cisco@...all.nl>
Cc:     dl-linux-imx <linux-imx@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "laurent.pinchart+renesas@...asonboard.com" 
        <laurent.pinchart+renesas@...asonboard.com>,
        Aisheng Dong <aisheng.dong@....com>,
        Laurentiu Palcu <laurentiu.palcu@....com>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        Robert Chiras <robert.chiras@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "paul.kocialkowski@...tlin.com" <paul.kocialkowski@...tlin.com>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "niklas.soderlund+renesas@...natech.se" 
        <niklas.soderlund+renesas@...natech.se>,
        Daniel Baluta <daniel.baluta@....com>,
        "dafna.hirschfeld@...labora.com" <dafna.hirschfeld@...labora.com>,
        "ezequiel@...labora.com" <ezequiel@...labora.com>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>
Subject: Re: [EXT] Re: [PATCH v5 07/10] media: Add parsing for APP14 data
 segment in jpeg helpers

On Fri, 2020-12-04 at 14:13 +0000, Mirela Rabulea (OSS) wrote:
> Hi Phipipp,
>
> On Wed, 2020-12-02 at 16:18 +0100, Philipp Zabel wrote:
> > Hi Mirela,
> > 
> > On Thu, 2020-11-12 at 05:05 +0200, Mirela Rabulea (OSS) wrote:
> > > From: Mirela Rabulea <mirela.rabulea@....com>
> > > 
> > > According to Rec. ITU-T T.872 (06/2012) 6.5.3
> > > APP14 segment is for color encoding, it contains a transform flag,
> > > which
> > > may have values of 0, 1 and 2 and are interpreted as follows:
> > > 0 - CMYK for images that are encoded with four components
> > >   - RGB for images that are encoded with three components
> > > 1 - An image encoded with three components using YCbCr colour
> > > encoding.
> > > 2 - An image encoded with four components using YCCK colour
> > > encoding.
> > > 
> > > This is used in imx-jpeg decoder, to distinguish between
> > > YUV444 and RGB24.
> > > 
> > > Signed-off-by: Mirela Rabulea <mirela.rabulea@....com>
> > > ---
> > > Changes in v5:
> > > This was patch 8 in previous version
> > > Replaced a struct for app14 data with just an int, since the
> > > transform flag is the only meaningfull information from this
> > > segment
> > 
> > Could we turn this into an enum for the transform flag, and include
> > the
> > above spec reference in its kerneldoc comment? I think this would be
> > better than checking for (app14_tf == <magic_number>) in the drivers.
> 
> Appreciate your feedback, for all patches, I'll address it in v6.
> Where would be a better place for this enum, v4l2-jpeg.h, or maybe
> include/uapi/linux/v4l2-controls.h?

v4l2-jpeg.h seems like the right place to me.

regards
Philipp