DRM planes and new fb creation ioctl

Joonyoung Shim jy0922.shim at samsung.com
Tue Oct 25 03:47:13 PDT 2011

Hi, Jesse.

Thanks for posting.

10/25/2011 06:46 PM, Jesse Barnes 쓴 글:
> I've given up waiting for someone to implement support for these ioctls
> on another platform before they're merged, but I have received a lot of
> feedback on the interfaces, and it sounds like they're ok.  I've also
> fixed all the remaining issues I'm aware of on SNB platforms and things
> are working well, so I'm just going to push them out.  (Note IVB support
> is still missing a few bits for scaling and such; I'll fix those up when
> I get back home and can test on IVB again.)
> One change you may notice from the last set is that I've removed the
> 'zpos' parameter.  Plane blending and z ordering is very chipset
> specific (it even varies between Intel chipsets), so exposing it through
> a device specific ioctl is probably a better plan.

But i think zpos is essential parameter of plane. If plane doesn't
support it, drm driver cannot know user wants to use which overlay,
so i wonder what it meant DRM_IOCTL_MODE_SETPLANE zpos is absent .

If use device specific ioctl, should implement device specific ioctl for

>    By default, planes
> should just overlay the primary plane; a device specific ioctl (none
> available yet, but I have some planned for i915) can provide more
> flexibility.

Could you explain what is the primary plane? Is it same as the overlay
handled by crtc? It confuses a bit when one overlay is handled by crtc
and plane at the same time.

> To recap previous posts, this patchset provides a few new interfaces:
>    - addfb2 - a new FB creation ioctl that lets you specify a surface
>      format, as defined by a fourcc code from the video4linux headers
>      (libdrm will wrap these in DRM_ macros for portability)
>    - planes - ioctls for fetching plane info and attaching an fb to a
>      plane; note there's no separate flip ioctl for planes, just use
>      setplane to update the fb
> The testdisplay.c program in intel-gpu-tools has support for testing
> these interfaces, and I'll be fixing up and pushing the
> xf86-video-intel support soon as well, so you can use either as a
> reference for how the new interfaces work.
> Thanks,
> Jesse
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