[PATCH] drm/tegra: Add zpos property for cursor planes

[Dmitry Osipenko]

11.06.2020 11:17, Daniel Stone пишет:
> Hi Dmitry,
> 
> On Thu, 11 Jun 2020 at 08:54, Dmitry Osipenko <digetx at gmail.com> wrote:
>> 10.06.2020 14:30, Thierry Reding пишет:
>>> From: Thierry Reding <treding at nvidia.com>
>>> As of commit 4dc55525b095 ("drm: plane: Verify that no or all planes
>>> have a zpos property") a warning is emitted if there's a mix of planes
>>> with and without a zpos property.
>>
>> What problem does it solve?
> 
> Well, it fixes the WARN_ON, which asserts that either no planes have
> the zpos property attached, or all planes have the zpos property
> attached. When only _some_ planes have the property, the property is
> pretty much useless: zpos exists to guarantee to userspace the
> relative ordering between planes, defined by the value of the
> property. If not all planes have the property, then userspace cannot
> reason about the ordering, since some of the planes have undefined
> ordering.

Hello Daniel,

So it's a kernel warning, thank you for the clarification! I'm running
only older Tegras that have a black-n-white cursor plane, but this is
not supported by the upstream kernel. No wonder that I haven't seen the
warning, this made me curious what this patch is about :)