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uapi/drm/drm_fourcc.h: Note on platform specificity for format modifiers

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Make an additional note on DRM format modifiers for x and y tiling. These
format modifiers are defined for BDW+ platforms and therefore definition
is not valid for older gens. This is due to address swizzling for tiled
surfaces is no longer used. For newer platforms main memory controller has
a more effective address swizzling algorithm.

v2: Rephrase comment (Daniel)

Signed-off-by: Mika Kahola <mika.kahola@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20200506120827.12250-1-mika.kahola@intel.com
This commit is contained in:
Mika Kahola 2020-05-06 15:08:27 +03:00 committed by Daniel Vetter
parent d6ddbd5c97
commit 50b6f619a0
1 changed files with 12 additions and 6 deletions
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18
include/uapi/drm/drm_fourcc.h
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@ -354,9 +354,12 @@ extern "C" {
* a platform-dependent stride. On top of that the memory can apply
* platform-depending swizzling of some higher address bits into bit6.
*
* This format is highly platforms specific and not useful for cross-driver
* sharing. It exists since on a given platform it does uniquely identify the
* layout in a simple way for i915-specific userspace.
* Note that this layout is only accurate on intel gen 8+ or valleyview chipsets.
* On earlier platforms the is highly platforms specific and not useful for
* cross-driver sharing. It exists since on a given platform it does uniquely
* identify the layout in a simple way for i915-specific userspace, which
* facilitated conversion of userspace to modifiers. Additionally the exact
* format on some really old platforms is not known.
*/
#define I915_FORMAT_MOD_X_TILED fourcc_mod_code(INTEL, 1)
@ -369,9 +372,12 @@ extern "C" {
* memory can apply platform-depending swizzling of some higher address bits
* into bit6.
*
* This format is highly platforms specific and not useful for cross-driver
* sharing. It exists since on a given platform it does uniquely identify the
* layout in a simple way for i915-specific userspace.
* Note that this layout is only accurate on intel gen 8+ or valleyview chipsets.
* On earlier platforms the is highly platforms specific and not useful for
* cross-driver sharing. It exists since on a given platform it does uniquely
* identify the layout in a simple way for i915-specific userspace, which
* facilitated conversion of userspace to modifiers. Additionally the exact
* format on some really old platforms is not known.
*/
#define I915_FORMAT_MOD_Y_TILED fourcc_mod_code(INTEL, 2)