[RFC] drm: add support for tiled/compressed/etc modifier in addfb2

[Daniel Stone]

Hi,

On 12 December 2014 at 18:22, Ville Syrjälä <ville.syrjala at linux.intel.com>
wrote:
>
> On Fri, Dec 12, 2014 at 06:05:49PM +0000, Daniel Stone wrote:
> > On 12 December 2014 at 18:00, Ville Syrjälä <
> ville.syrjala at linux.intel.com>
> > wrote:
> > > Well anyone who is serious about quality ought to handle that stuff.
> > > Or at least make sure both GL/whatever and planes ignore the hints in
> > > the same way. So if you GL implementation is lax then you anyway need
> > > to have some driver/hardware specific knowledge to know which way to go
> > > when using the plane path to get matching output.
> > >
> >
> > Anyone who's serious about quality and is also using GL for video, is not
> > serious about quality. Or accurate timing.
>
> You're too hung up on the "GL" there. It doesn't actually matter what
> you use to render the video when not using the display hardware. The
> same problem remains.


Yes, the problem being that sometimes you want to force the hardware to do
exactly what you want and literally nothing else, and sometimes you don't
care.

I posit that a hint-with-optional-force interface is best, because:
  - if your hint isn't supported, what do you do? fall back to software?
  - the number of people who care enough to force it is vanishingly small,
which is partly shown by how:
  - it matches GL semantics
  - not a great deal of hardware supports them


> > > I was more thinking of some global "I want exactly what I said" kind
> > > of knob. Maybe as a client cap type of thingy.
> >
> > I like the idea of keeping it local to the chroma-siting/range hints,
> > because it makes it far more clear exactly what it affects.
>
> You're not thinking wide enough. We would need to add similar hints
> to pretty much every property.


Which other properties do we have right now that drivers treat as optional
hints? If the answer involves hypothetical new properties, what are they?

Cheers,
Daniel
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