Re: [PATCHv4 04/13] drm/shmobile: Restrict plane loops to only operate on legacy planes

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Mar 28, 2014 at 06:52:50PM +0100, Daniel Vetter wrote:
> On Fri, Mar 28, 2014 at 04:50:13PM +0100, Laurent Pinchart wrote:
> > Hi Matt,
> > 
> > Thank you for the patch.
> > 
> > On Thursday 27 March 2014 17:44:29 Matt Roper wrote:
> > > Ensure that existing driver loops over all planes do not change behavior
> > > when we begin adding new types of planes (primary and cursor) to the DRM
> > > plane list in future patches.
> > > 
> > > Cc: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> > > Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
> > 
> > Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> > 
> > I have a question though. The patch set introduces three plane types, OVERLAY, 
> > PRIMARY and CURSOR. What should a driver that has no concept of primary plane 
> > do ? Expose all planes as OVERLAY planes only ?
> 
> It's a matter of backwards compat with old userspace. primary/cursor are
> simply ways to tell the drm core which planes to use to forward the legacy
> cursor crtc and which plane will be used for the framebuffer in setCrtc.
> 
> So until we have the new atomic interface ready your driver kinda needs to
> expose at least a primary plane, otherwise there's no way to even switch
> on the crtc.
> 
> But besides this backwards compat issue there's no difference and you can
> specify whatever plane you want as primary/cursor (or none if you don't
> care about old userspace).

Well the NULL primary plane probably needs a bit of work on top of Matt's
patch series here ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch