[PATCH] drm/atomic-helper: Calculate normalized zpos values

[Daniel Vetter]

On Mon, Nov 13, 2017 at 09:56:19PM +0100, Thierry Reding wrote:
> On Mon, Nov 13, 2017 at 04:14:05PM +0200, Ville Syrjälä wrote:
> > On Mon, Nov 13, 2017 at 02:48:20PM +0100, Thierry Reding wrote:
> > > From: Thierry Reding <treding at nvidia.com>
> > > 
> > > kerneldoc for drm_plane_create_zpos_property() says that the DRM core
> > > will automatically calculate the normalized zpos values, but it won't
> > > currently do so. Modify the atomic helpers to behave as documented.
> > 
> > NAK
> > 
> > See commit  38d868e41c4b ("drm: Don't force all planes to be added to
> > the state due to zpos")
> 
> Thanks, that's interesting background. It's a little unfortunate that
> I'll have to go and add a custom ->atomic_check() just because of this.

I'm behind on mails still, but is there a patch to fix the misleading
kerneldoc?
-Daniel

> 
> This is something in general that's been bugging me. How are we supposed
> to keep all of the custom ->atomic_check() implementations in sync with
> the atomic helpers? It looks to me like most drivers will at some point
> copy the atomic helper to their driver and then make driver-specific
> changes to them. But then when one of the helpers gets updated, the same
> changes are usually not propagated to the drivers that originally copied
> from the helpers.
> 
> One way I've seen used (and have used myself) occasionally is for the
> driver-specific implementations to "subclass" the helpers by calling the
> helper first and then calling the driver-specific bits. That helps a lot
> but will obviously not work if ordering is important.
> 
> Any ideas on how we can improve that? Other than periodically checking
> the git log for the helpers and updating drivers? I suppose if one were
> to closely follow the mailing list one might notice early on, and maybe
> speak up and have the changes applied to the drivers in the same patch
> as the helpers. But I don't think that's going to work for every driver.
> 
> Thierry



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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch