linux-kernel - Re: dt-bindings: display: xlnx: mixer: Inconsistent pixel format terminology in dt docs

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Date:   Mon, 24 Aug 2020 02:17:37 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Hyun Kwon <hyun.kwon@...inx.com>
Cc:     Kenneth Sloat <ksloat@...ignlinxhs.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Michal Simek <michals@...inx.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>
Subject: Re: dt-bindings: display: xlnx: mixer: Inconsistent pixel format
 terminology in dt docs

Hello,

On Thu, Aug 20, 2020 at 04:38:18PM -0700, Hyun Kwon wrote:
> On Thursday, August 20, 2020 2:18 PM, Kenneth Sloat write:
> > Hello,
> > 
> > The Xilinx Video mixer IP uses the DRM fourcc string as a device tree binding in
> > order to describe the format for a specific DRM layer/plane. Currently, in the
> > device tree doc in
> > "Documentation/devicetree/bindings/dma/xilinx/xilinx_frmbuf.txt" there is a list
> > called "VIDEO FORMATS" with a table containing "Mixer IP Format" and
> > associated "Driver supported Format String" (fourcc). In general, this table is not
> > helpful, because "Mixer IP Format" does not match the Xilinx IP datasheet
> > terminology for formats but rather some other commonly used nomenclature.
> > This is also inconsistent from other Xilinx dts binding docs which specify the
> > actual correct IP name and at times list other format nomenclature where
> > helpful (i.e. xilinx_frmbuf.txt)
> > 
> > My suggestion is to remove the current "Mixer IP Format" strings in the doc and
> > replace them with the actual IP names in the datasheet (which also match those
> > used in Xilinx's Vivado FPGA tool). Otherwise, the programmer must cross
> > reference other dts documentation or the code in order to figure these out. I am
> > happy to provide a patch for this but wanted to throw out the suggestion first.

Are you talking about the "Video Format" column in table 2-8 of PG243 ?
Those values seem good to me.

Documentation/devicetree/bindings/media/xilinx/video.txt also defines a
xlnx,video-format property that uses the values from UG934 for the AXI
streaming interface.

> I agree. The bindings should be in sync with datasheet and not rely on
> software definitions. Since the driver is only in Xilinx vendor tree,
> please send directly to git@...inx.com.

-- 
Regards,

Laurent Pinchart