[Intel-gfx] [RFC 2/2] drm/i915: Render decompression support for Gen9

[Daniel Stone]

Hi Vandana,

On 23 December 2015 at 03:20, Kannan, Vandana <vandana.kannan at intel.com> wrote:
> How does VT switch work in case of rotation, setting different pixel format,
> etc?

Pixel format is a property of the framebuffer, not a per-plane
property, so is unaffected. Rotation is generic, so there is specific
code to handle it for fbdev etc.

But the real problem is that this is an Intel-specific property, and
in order to get correct results, userspace must know about these
specific properties in order to unset them. This means that you can't
run generic userspace, and you can't run old userspace which predates
these properties either. This seems like a total non-starter to me.

It would be much cleaner if there was a way to attach the render
compression property to the framebuffer, e.g. by using the format
modifiers which were specifically introduced to deal with compression
and tiling.

Cheers,
Daniel