display band (display area vs real visible area)

[Daniel Stone]

Hi,

On Tue, 21 Mar 2023 at 12:08, Jani Nikula <jani.nikula at linux.intel.com> wrote:
> On Tue, 21 Mar 2023, Daniel Stone <daniel at fooishbar.org> wrote:
> > There have been some threads - mostly motivated by MacBooks and the
> > Asahi team - about creating a KMS property to express invisible areas.
> > This would be the same thing, and the userspace ecosystem will pick it
> > up when the kernel exposes it.
>
> In my case the kernel handled it completely internally, and the
> userspace didn't even know. But I guess it depends on the display being
> able to take a smaller framebuffer, otherwise I don't think it's
> feasible.
>
> I haven't checked the threads you mention but I assume it covers the
> more general case of having rounded corners or holes for the camera, not
> just the frame covering the edges or something like that. That couldn't
> possibly be handled by kernel alone, but it's also a bunch of
> infrastructure work both in kernel and userspace to make it happen.

Yeah, exactly. Just a connector property, which could come from DT or
ACPI or manual overrides or whatever. Userspace would still allocate a
full-size framebuffer, but look at that property and not render
anything useful into those areas. In the camera/notch case, it's a
matter of not putting useful content there. In the letterbox/pillarbox
case, it's about shrinking the reported screen size so that window
management, clients, etc, all believe that the screen is smaller than
it is.

Cheers,
Daniel