linux-kernel - Re: [PATCH v2 2/2] dt-bindings: display: simple-framebuffer: Document physical width and height properties

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Date:   Sun, 22 Jan 2023 16:42:22 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Rob Herring <robh+dt@...nel.org>, Rayyan Ansari <rayyan@...ari.sh>
Cc:     dri-devel@...ts.freedesktop.org,
        ~postmarketos/upstreaming@...ts.sr.ht, asahi@...ts.linux.dev,
        janne@...nau.net, Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...il.com>, devicetree@...r.kernel.org,
        Javier Martinez Canillas <javierm@...hat.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH v2 2/2] dt-bindings: display: simple-framebuffer: Document
 physical width and height properties

Hi,

On 1/22/23 16:36, Rob Herring wrote:
> On Sat, Jan 21, 2023 at 9:36 AM Rayyan Ansari <rayyan@...ari.sh> wrote:
>>
> 
> Why do you need this change?
> 
> The 'simple-framebuffer' contains data on how the bootloader
> configured the display. The bootloader doesn't configure the display
> size, so this information doesn't belong here. The information should
> already be in the panel node, so also no point in duplicating it here.

The idea is that early boot code which uses the simplefb node (no more
complex display driver loaded yet) knows the panel's DPI so that it can
decide if hi-dpi rendering / scaling is necessary or not.

This definitely is a useful feature to have.

I guess that for dt systems an alternative approach could be to
add a link to the panel node to the simplefb dt-node.

Regards,

Hans