linux-kernel - Re: [PATCH v7 04/23] dt-bindings: display: mediatek: padding: Add MT8188

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Message-ID: <cadc280e7be3c14687bd4ef4f4fe6b459120396c.camel@mediatek.com>
Date:   Tue, 17 Oct 2023 04:19:46 +0000
From:   Shawn Sung (宋孝謙) 
        <Shawn.Sung@...iatek.com>
To:     "daniel@...ishbar.org" <daniel@...ishbar.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Singo Chang (張興國) 
        <Singo.Chang@...iatek.com>,
        Jason-JH Lin (林睿祥) 
        <Jason-JH.Lin@...iatek.com>,
        "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Nancy Lin (林欣螢) <Nancy.Lin@...iatek.com>,
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        CK Hu (胡俊光) <ck.hu@...iatek.com>,
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        <angelogioacchino.delregno@...labora.com>
Subject: Re: [PATCH v7 04/23] dt-bindings: display: mediatek: padding: Add
 MT8188

Hi Daniel,

On Mon, 2023-10-16 at 12:47 +0200, Daniel Stone wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  Hi Shawn,
> 
> On Mon, 16 Oct 2023 at 06:23, Shawn Sung (宋孝謙) <
> Shawn.Sung@...iatek.com> wrote:
> > On Fri, 2023-10-13 at 17:26 +0100, Daniel Stone wrote:
> > > If I understand the driver correctly, padding is automatically
> > > applied
> > > to compensate for unaligned dimensions. The first/last
> rows/columns
> > > of
> > > the overlay area will be filled with a specified colour (black?)
> to
> > > preserve the area. This is unfortunately not OK to do
> transparently.
> > > Userspace must be aware of this policy decision and specifically
> > > request it. If not, the atomic request check should fail and tell
> > > userspace that the requested configuration is not possible to
> > > achieve.
> >
> > Yes, Padding works as you described, users can assign background
> colors
> > for the filled area in 10bit RGB format, however, the rows and
> columns
> > that are filled by Padding will be cropped by the hardware
> components
> > after it to avoid situations as you mentioned, so users should not
> > notice any difference.
> 
> Thanks for the explanation, I hadn't realised that the added padding
> later gets cropped.
> 
> Cheers,
> Daniel

Since Padding is bypassed in the current version, we didn't mention too
many details about it. Thank you for checking.

For more information, 4-pixel alignment in width is only required when
HDR is in Dolby Vision format, and the paddings will be cropped by
video front-end in the HDR module.

Cheers,
Shawn