Re: [Intel-gfx] [RFC 2/6] drm/i915: Add tiled framebuffer modifiers

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, Feb 02, 2015 at 10:41:24AM +0100, Daniel Vetter wrote:
> On Fri, Jan 30, 2015 at 05:36:54PM +0000, Tvrtko Ursulin wrote:
> > From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > 
> > To be used from the new addfb2 extension.
> > 
> > Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
> > ---
> >  include/uapi/drm/i915_drm.h | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> > 
> > diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> > index 6eed16b..a7327fd 100644
> > --- a/include/uapi/drm/i915_drm.h
> > +++ b/include/uapi/drm/i915_drm.h
> > @@ -28,6 +28,7 @@
> >  #define _UAPI_I915_DRM_H_
> >  
> >  #include <drm/drm.h>
> > +#include <uapi/drm/drm_fourcc.h>
> >  
> >  /* Please note that modifications to all structs defined here are
> >   * subject to backwards-compatibility constraints.
> > @@ -1101,4 +1102,16 @@ struct drm_i915_gem_context_param {
> >  	__u64 value;
> >  };
> >  
> > +/** @{
> > + * Intel framebuffer modifiers
> > + *
> > + * Tiling modes supported by the display hardware
> > + * to be passed in via the DRM addfb2 ioctl.
> > + */
> > +/** None */
> > +#define I915_FORMAT_MOD_NONE	fourcc_mod_code(INTEL, 0x00000000000000L)
> > +/** X tiling */
> > +#define I915_FORMAT_MOD_X_TILED	fourcc_mod_code(INTEL, 0x00000000000001L)
> 
> One thing I wonder here is whether we should have a modifier for each
> physical layout (tiling modes do change slightly between hw) or whether we
> should just continue to assume that this is Intel-specific and add a
> disclaimer that the precise layout depends upon the actual intel box
> you're running on?
> 
> Leaning towards your approach, worst case we get to write some code to
> de-alias layout modifiers with established cross-vendor layouts (if they
> ever happen). Just want to make sure that we've thought about this. Adding
> Rob&dri-devel for this.

Something else to ponder: We also need layout modifiers for non-fb formats
in userspace so that clients and compositors can communicate about render
formats. Given that I think it'll make sense to enumerate all the other
tiling formats we have, too (i.e. Y-tiled and W-tiled).
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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