From: Mika Kahola Date: Wed, 6 May 2020 12:08:27 +0000 (+0300) Subject: uapi/drm/drm_fourcc.h: Note on platform specificity for format modifiers X-Git-Tag: baikal/mips/sdk5.9~13559^2~9^2~15 X-Git-Url: https://git.baikalelectronics.ru/sdk/?a=commitdiff_plain;h=24a14eeada74cb48c45e06b34faed45e1cdaa71f;p=kernel.git uapi/drm/drm_fourcc.h: Note on platform specificity for format modifiers 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 Signed-off-by: Daniel Vetter Link: https://patchwork.freedesktop.org/patch/msgid/20200506120827.12250-1-mika.kahola@intel.com --- diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h index 8bc0b31597d80..9e488d10f8b40 100644 --- a/include/uapi/drm/drm_fourcc.h +++ b/include/uapi/drm/drm_fourcc.h @@ -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)