docs: start some documentation on Anv

Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14522>

docs/drivers/anv.rst

@@ -0,0 +1,142 @@
+ANV
+===
+
+.. _`Bindless model`:
+
+Binding Model
+-------------
+
+Here is the Anv bindless binding model that was implemented for the
+descriptor indexing feature of Vulkan 1.2 :
+
+.. graphviz::
+
+  digraph G {
+    fontcolor="black";
+    compound=true;
+
+    subgraph cluster_1 {
+      label = "Binding Table (HW)";
+
+      bgcolor="cornflowerblue";
+
+      node [ style=filled,shape="record",fillcolor="white",
+             label="RT0"    ] n0;
+      node [ label="RT1"    ] n1;
+      node [ label="dynbuf0"] n2;
+      node [ label="set0"   ] n3;
+      node [ label="set1"   ] n4;
+      node [ label="set2"   ] n5;
+
+      n0 -> n1 -> n2 -> n3 -> n4 -> n5 [style=invis];
+    }
+    subgraph cluster_2 {
+      label = "Descriptor Set 0";
+
+      bgcolor="burlywood3";
+      fixedsize = true;
+
+      node [ style=filled,shape="record",fillcolor="white", fixedsize = true, width=4,
+             label="binding 0 - STORAGE_IMAGE\n anv_storage_image_descriptor"          ] n8;
+      node [ label="binding 1 - COMBINED_IMAGE_SAMPLER\n anv_sampled_image_descriptor" ] n9;
+      node [ label="binding 2 - UNIFORM_BUFFER\n anv_address_range_descriptor"         ] n10;
+      node [ label="binding 3 - UNIFORM_TEXEL_BUFFER\n anv_storage_image_descriptor"   ] n11;
+
+      n8 -> n9 -> n10 -> n11 [style=invis];
+    }
+    subgraph cluster_5 {
+      label = "Vulkan Objects"
+
+      fontcolor="black";
+      bgcolor="darkolivegreen4";
+
+      subgraph cluster_6 {
+        label = "VkImageView";
+
+        bgcolor=darkolivegreen3;
+        node [ style=filled,shape="box",fillcolor="white", fixedsize = true, width=2,
+               label="surface_state" ] n12;
+      }
+      subgraph cluster_7 {
+        label = "VkSampler";
+
+        bgcolor=darkolivegreen3;
+        node [ style=filled,shape="box",fillcolor="white", fixedsize = true, width=2,
+               label="sample_state" ] n13;
+      }
+      subgraph cluster_8 {
+        label = "VkImageView";
+        bgcolor="darkolivegreen3";
+
+        node [ style=filled,shape="box",fillcolor="white", fixedsize = true, width=2,
+               label="surface_state" ] n14;
+      }
+      subgraph cluster_9 {
+        label = "VkBuffer";
+        bgcolor=darkolivegreen3;
+
+        node [ style=filled,shape="box",fillcolor="white", fixedsize = true, width=2,
+               label="address" ] n15;
+      }
+      subgraph cluster_10 {
+        label = "VkBufferView";
+
+        bgcolor=darkolivegreen3;
+        node [ style=filled,shape="box",fillcolor="white", fixedsize = true, width=2,
+               label="surface_state" ] n16;
+      }
+
+      n12 -> n13 -> n14 -> n15 -> n16 [style=invis];
+    }
+
+    subgraph cluster_11 {
+      subgraph cluster_12 {
+        label = "CommandBuffer state stream";
+
+        bgcolor="gold3";
+        node [ style=filled,shape="box",fillcolor="white", fixedsize = true, width=2,
+               label="surface_state" ] n17;
+        node [ label="surface_state" ] n18;
+        node [ label="surface_state" ] n19;
+
+        n17 -> n18 -> n19 [style=invis];
+      }
+    }
+
+    n3  -> n8 [lhead=cluster_2];
+
+    n8  -> n12;
+    n9  -> n13;
+    n9  -> n14;
+    n10 -> n15;
+    n11 -> n16;
+
+    n0 -> n17;
+    n1 -> n18;
+    n2 -> n19;
+  }
+
+
+
+The HW binding table is generated when the draw or dispatch commands
+are emitted. Here are the types of entries one can find in the binding
+table :
+
+- The currently bound descriptor sets, one entry per descriptor set
+  (our limit is 8).
+
+- For dynamic buffers, one entry per dynamic buffer.
+
+- For draw commands, render target entries if needed.
+
+The entries of the HW binding table for descriptor sets are
+RENDER_SURFACE_STATE similar to what you would have for a normal
+uniform buffer. The shader will emit reads this buffer first to get
+the information it needs to access a surface/sampler/etc... and then
+emits the appropriate message using the information gathered from the
+descriptor set buffer.
+
+Each binding type entry gets an associated structure in memory
+(``anv_storage_image_descriptor``, ``anv_sampled_image_descriptor``,
+``anv_address_range_descriptor``, ``anv_storage_image_descriptor``).
+This is the information read by the shader.

docs/index.rst

@@ -83,6 +83,7 @@ Linux, FreeBSD, and other operating systems.
    :caption: Drivers
    :hidden:
 
+   drivers/anv
    drivers/d3d12
    drivers/freedreno
    drivers/lima