Re: [PATCH v2 1/7] dt-bindings: display: simple-framebuffer: Support system memory framebuffers

[Thierry Reding <thierry.reding@gmail.com>]

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On Mon, Oct 10, 2022 at 11:37:37AM +0200, Thomas Zimmermann wrote:
> Hi
> 
> Am 07.10.22 um 14:49 schrieb Thierry Reding:
> > From: Thierry Reding <treding@nvidia.com>
> > 
> > In order to support framebuffers residing in system memory, allow the
> > memory-region property to override the framebuffer memory specification
> > in the "reg" property.
> 
> What happens if both properties are present and they disagree with each
> other?
> 
> I understand that the framebuffer is behind 'memory-region', but does 'reg'
> still contain device memory?  Do we need to acquire ownership from within
> the driver?

The intention is for both memory-region and reg properties to be
mutually exclusive. I can't think of a scenario where you would need or
want both.

Note also the documentation for the memory-region property:

|  memory-region:
|    maxItems: 1
|    description: Phandle to a node describing the memory to be used for the
|      framebuffer. If present, overrides the "reg" property (if one exists).

Thierry

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