[PATCH 5/5] drm/exynos: Add plane support with fimd

[Inki Dae]

Hi, Rob.
below is my answer.

> -----Original Message-----
> From: Rob Clark [mailto:robdclark at gmail.com]
> Sent: Tuesday, December 13, 2011 9:48 AM
> To: Joonyoung Shim
> Cc: Inki Dae; kyungmin.park at samsung.com; sw0312.kim at samsung.com; dri-
> devel at lists.freedesktop.org
> Subject: Re: [PATCH 5/5] drm/exynos: Add plane support with fimd
> 
> On Mon, Dec 12, 2011 at 6:41 PM, Joonyoung Shim <jy0922.shim at samsung.com>
> wrote:
> > On 12/13/2011 06:59 AM, Rob Clark wrote:
> >>
> >> On Fri, Dec 9, 2011 at 4:59 AM, Inki Dae<inki.dae at samsung.com>  wrote:
> >>>
> >>> From: Joonyoung Shim<jy0922.shim at samsung.com>
> >>>
> >>> The exynos fimd supports 5 window overlays. Only one window overlay of
> >>> fimd is used by the crtc, so we need plane feature to use the rest
> >>> window overlays.
> >>>
> >>> This creates one ioctl exynos specific - DRM_EXYNOS_PLANE_SET_ZPOS, it
> >>> is the ioctl to decide for user to assign which window overlay.
> >>>
> >> btw, I think I will end up with a similar ioctl.. so thought I'd
> >> double check for consistency, is zorder interpreted from back to front
> >> or front to back?  Ie. higher numeric value in front or behind of
> >> lower numeric value?  Are negative values permitted?
> >
> >
> > The zpos of exynos plane is just the index of overlay of exynos fimd or
> > exynos hdmi. 0 zpos means first overlay and 1 zpos means second overlay.
> > It isn't the priority value but higher zpos will have higher priority
> > generally.
> 
> I'm not sure that I quite understand that.. does that mean zpos=1 will
> be in front of zpos=0 (which would be in front of crtc, aka zpos=-1).
> Do you have a way to put overlays *behind* crtc layer (which
> presumably would be in some mode with an alpha channel?)
> 
> (IIRC, samsung has some public TRM type document.. if this is covered
> there, feel free to answer by just pointing me at the section I should
> read)
> 

I know that omap, at least omap3(Display Controller of the Display
Subsystem), has two modes. one is normal mode and another is alpha mode. and
they also have different overlay priority but Samsung exynos has fixed
priority to hardware overlays. so higher overlay always is in front of lower
overlay. in case of plane module for Samsung SoC, if zpos is -1 then crtc
has default overlay designated by machine code. so whether some overlay is
in front of crtc or not would be decided by default overlay.

Thank you,
Inki Dae.


> BR,
> -R
> 
> > A negative value -1 is defined to special value. A exynos crtc should
> > use one overlay and -1 zpos means the overlay that crtc uses.
> >
> > Thanks.
> >
> >> BR,
> >> -R
> >>
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> >>
> >