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

[Daniel Vetter]

On Mon, Feb 02, 2015 at 10:23:57AM +0000, Tvrtko Ursulin wrote:
> 
> On 02/02/2015 09:58 AM, Daniel Vetter wrote:
> >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 at intel.com>
> >>>
> >>>To be used from the new addfb2 extension.
> >>>
> >>>Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin at 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).
> 
> If we need fb modifiers for non-fb formats, although that sounds a bit funky
> to me, we can always add them in separate patches, no?

Yes and no - I think the aliasing with the I915_TILING_FOO defines would
be nice, and if you reserve another number for the fancy new tiling you're
working on and so block Y-tiled that would be unfortunate ...

Otoh meh, we need to remap anyway sooner or later. Like I've said, just
something to consider.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch