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Contents of README:Intel Surface Layout Introduction ============ isl is a small library that calculates the layout of Intel GPU surfaces, queries those layouts, and queries the properties of surface formats. Independence from User APIs =========================== isl's API is independent of any user-facing graphics API, such as OpenGL and Vulkan. This independence allows isl to be used a shared component by multiple Intel drivers. Rather than mimic the user-facing APIs, the isl API attempts to reflect Intel hardware: the actual memory layout of Intel GPU surfaces and how one programs the GPU to use those surfaces. For example: - The tokens of `enum isl_format` (such as `ISL_FORMAT_R8G8B8A8_UNORM`) match those of the hardware enum `SURFACE_FORMAT` rather than the OpenGL or Vulkan format tokens. And the values of `isl_format` and `SURFACE_FORMAT` are identical. - The OpenGL and Vulkan APIs contain depth and stencil formats. However the hardware enum `SURFACE_FORMAT` does not, and therefore neither does `enum isl_format`. Rather than define new pixel formats that have no hardware counterpart, isl records the intent to use a surface as a depth or stencil buffer with the usage flags `ISL_SURF_USAGE_DEPTH_BIT` and `ISL_SURF_USAGE_STENCIL_BIT`. - `struct isl_surf` distinguishes between the surface's logical dimension from the user API's perspective (`enum isl_surf_dim`, which may be 1D, 2D, or 3D) and the layout of those dimensions in memory (`enum isl_dim_layout`). Surface Units ============= Intro ----- ISL takes care in its equations to correctly handle conversion among surface units (such as pixels and compression blocks) and to carefully distinguish between a surface's logical layout in the client API and its physical layout in memory. Symbol names often explicitly declare their unit with a suffix: - px: logical pixels - sa: physical surface samples - el: physical surface elements - sa_rows: rows of physical surface samples - el_rows: rows of physical surface elements Logical units are independent of hardware generation and are closely related to the user-facing API (OpenGL and Vulkan). Physical units are dependent on hardware generation and reflect the surface's layout in memory. Definitions ----------- - Logical Pixels (px): The surface's layout from the perspective of the client API (OpenGL and Vulkan) is in units of logical pixels. Logical pixels are independent of the surface's layout in memory. A surface's width and height, in units of logical pixels, is not affected by the surface's sample count. For example, consider a VkImage created with VkImageCreateInfo{width=w0, height=h0, samples=s0}. The surface's width and height at level 0 is, in units of logical pixels, w0 and h0 regardless of the value of s0. For example, the logical array length of a 3D surface is always 1, even on Gen9 where the surface's memory layout is that of an array surface (ISL_DIM_LAYOUT_GEN4_2D). - Physical Surface Samples (sa): For a multisampled surface, this unit has the obvious meaning. A singlesampled surface, from ISL's perspective, is simply a multisampled surface whose sample count is 1. For example, consider a 2D single-level non-array surface with samples=4, width_px=64, and height_px=64 (note that the suffix 'px' indicates logical pixels). If the surface's multisample layout is ISL_MSAA_LAYOUT_INTERLEAVED, then the extent of level 0 is, in units of physical surface samples, width_sa=128, height_sa=128, depth_sa=1, array_length_sa=1. If ISL_MSAA_LAYOUT_ARRAY, then width_sa=64, height_sa=64, depth_sa=1, array_length_sa=4. - Physical Surface Elements (el): This unit allows ISL to treat compressed and uncompressed formats identically in many calculations. If the surface's pixel format is compressed, such as ETC2, then a surface element is equivalent to a compression block. If uncompressed, then a surface element is equivalent to a surface sample. As a corollary, for a given surface a surface element is at least as large as a surface sample. Errata ------ ISL acquired the term 'surface element' from the Broadwell PRM [1], which defines it as follows: An element is defined as a pixel in uncompresed surface formats, and as a compression block in compressed surface formats. For MSFMT_DEPTH_STENCIL type multisampled surfaces, an element is a sample. References ========== [1]: Broadwell PRM >> Volume 2d: Command Reference: Structures >> RENDER_SURFACE_STATE Surface Vertical Alignment (p325) |
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Parent Directory -
CVS/ 19-Mar-2020 23:41 -
tests/ 19-Mar-2020 23:39 -
README 10-Mar-2019 04:42 4.5K
gen_format_layout.py 10-Mar-2019 04:42 9.1K
isl.c 10-Mar-2019 04:42 88K
isl.h 10-Mar-2019 04:42 76K
isl_drm.c 10-Mar-2019 04:42 2.9K
isl_emit_depth_stencil.c 10-Mar-2019 04:42 7.5K
isl_format.c 10-Mar-2019 04:42 47K
isl_format_layout.c 10-Mar-2019 04:42 135K
isl_format_layout.csv 10-Mar-2019 04:42 31K
isl_gen4.c 10-Mar-2019 04:42 5.0K
isl_gen4.h 10-Mar-2019 04:42 2.1K
isl_gen6.c 10-Mar-2019 04:42 5.2K
isl_gen6.h 10-Mar-2019 04:42 1.9K
isl_gen7.c 10-Mar-2019 04:42 16K
isl_gen7.h 10-Mar-2019 04:42 2.1K
isl_gen8.c 10-Mar-2019 04:42 6.9K
isl_gen8.h 10-Mar-2019 04:42 1.9K
isl_gen9.c 10-Mar-2019 04:42 8.2K
isl_gen9.h 10-Mar-2019 04:42 1.7K
isl_genX_priv.h 10-Mar-2019 04:42 2.0K
isl_priv.h 10-Mar-2019 04:42 4.7K
isl_storage_image.c 10-Mar-2019 04:42 11K
isl_surface_state.c 10-Mar-2019 04:42 27K
meson.build 10-Mar-2019 04:42 2.8K
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