16 bpc fixed point (RGBA16) framebuffer support for core and AMD.

[Ville Syrjälä]

On Fri, Apr 16, 2021 at 06:27:23PM +0200, Mario Kleiner wrote:
> On Mon, Mar 22, 2021 at 4:52 PM Ville Syrjälä
> <ville.syrjala at linux.intel.com> wrote:
> >
> > On Fri, Mar 19, 2021 at 10:03:12PM +0100, Mario Kleiner wrote:
> > > Hi,
> > >
> > > this patch series adds the fourcc's for 16 bit fixed point unorm
> > > framebuffers to the core, and then an implementation for AMD gpu's
> > > with DisplayCore.
> > >
> > > This is intended to allow for pageflipping to, and direct scanout of,
> > > Vulkan swapchain images in the format VK_FORMAT_R16G16B16A16_UNORM.
> > > I have patched AMD's GPUOpen amdvlk OSS driver to enable this format
> > > for swapchains, mapping to DRM_FORMAT_XBGR16161616:
> > > Link: https://github.com/kleinerm/pal/commit/a25d4802074b13a8d5f7edc96ae45469ecbac3c4
> >
> > We should also add support for these formats into igt.a Should
> > be semi-easy by just adding the suitable float<->uint16
> > conversion stuff.
> >
> 
> Hi Ville,
> 
> Could you point me to a specific test case / file that I should look
> at for adding this?

lib/igt_fb.c is the main thing. It has a bunch of conversion magic
to support rendering into all kinds of weird framebuffer formats
via cairo. 

In this should be mostly a matter of adding convert_uint16_to_float()
and convert_float_to_uint16(), plugging those into fb_convert(),
and declaring the new formats in format_desc[]. There might be
a few little extra details I'm forgetting though.

Once igt_fb has the required stuff kms_plane/pixel-format*
should automagically pick it up if the kernel reports the
format as supported.

Oh, and you need some >1.17 version of cairo for the float
support.

-- 
Ville Syrjälä
Intel