On Sun, Jan 22, 2023 at 05:25:38PM +0000, Rayyan Ansari wrote:

On 22/01/2023 15:36, Rob Herring wrote:

quoted

On Sat, Jan 21, 2023 at 9:36 AM Rayyan Ansari [off-list ref] wrote:

quoted

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.

quoted

Signed-off-by: Rayyan Ansari <redacted>
---
  .../devicetree/bindings/display/simple-framebuffer.yaml   | 8 ++++++++
  1 file changed, 8 insertions(+)

Hi Rob,

There is the usecase that Hans has mentioned, but I have also mentioned
another usecase previously.

Adding the width-mm and height-mm properties allows user interfaces such as
Phosh (https://puri.sm/posts/phosh-overview/) to scale correctly to the
screen. In my case, a panel node is not available and the aforementioned
interface is in fact running on the SimpleDRM driver (which binds to the
simple-framebuffer device).

Why is the panel node not available? Why not add it? Presumably it is 
not there because you aren't (yet) using the simple-panel driver (and 
others that would need). But presumably you will eventually as I'd 
imagine turning the screen off and back on might be a desired feature.

So why add a temporary DT property that's tied to your *current* kernel? 
The DT should not be tightly coupled to the kernel.

Rob