layers: update documentation

2 files changed, 18 insertions, 12 deletions

diff --git a/layers/README.md b/layers/README.md
index 039fe0e1..ec5882c8 100644
--- a/layers/README.md
+++ b/layers/README.md
@@ -12,19 +12,25 @@ activated at xglCreateDevice time. xglCreateDevice createInfo struct is extended
 a list of layers to be activated.  Layer libraries can alternatively be LD_PRELOADed.
 
 Layer library example code:
-layer/basic_plugin.c - simple example
-<build dir>/layer/generic_layer.c - auto generated example wrapping all XGL entrypoints
+include/xglLayer.h  - header file for layer code
+layer/basic_plugin.c  - simple example wrapping three entrypoints. Single global dispatch
+                        table for either single gpu/device or multi-gpu with same activated
+                        layers for each device. Can be LD_PRELOADed individually.
+<build dir>/layer/generic_layer.c  - auto generated example wrapping all XGL entrypoints.
+                                     Single global dispatch table. Can be LD_PRELOADed.
 <build dir>/layer/api_dump.c - print out API calls along with parameter values
 <build dir>/layer/object_track.c - Print object CREATE/USE/DESTROY stats
 
-Using Layers::
-Build XGL loader and i965 icd driver using normal steps (cmake and make)
-Place libXGLLayer<name>.so in the same directory as your XGL test or app:
+Using Layers:
+1) Build XGL loader  and i965 icd driver using normal steps (cmake and make)
+
+2) Place libXGLLayer<name>.so in the same directory as your XGL test or app:
   cp build/layer/libXGLLayerBasic.so build/layer/libXGLLayerGeneric.so build/tests
+This is required for the Icd loader to be able to scan and enumerate your library.
 
-Specify which Layers to activate by using xglCreateDevice XGL_LAYER_CREATE_INFO struct or
-environment variable LIBXGL_LAYERS_LIB
-   export LIBXGL_LAYERS_LIB=libXGLLayerBasic.so:LibXGLLayerGeneric.so
+3) Specify which Layers to activate by using xglCreateDevice XGL_LAYER_CREATE_INFO struct or
+environment variable LIBXGL_LAYER_LIBS
+   export LIBXGL_LAYER_LIBS=libXGLLayerBasic.so:LibXGLLayerGeneric.so
    cd build/tests; ./xglinfo
 
 
@@ -33,8 +39,8 @@ Current Features:
 -scanning of available Layers during xglInitAndEnumerateGpus
 -xglEnumerateLayers and xglGetProcAddr supported APIs in xgl.h, ICD loader and i965 driver
 -multiple layers in a hierarchy supported
--layer enumeration works
--layers activated per gpu and per icd driver: separate dispatch table and layer library
+-layer enumeration supported
+-layers  activated per gpu and per icd driver: separate  dispatch table and layer library
    list in loader for each gpu or icd driver
 -activation via xglCreateDevice extension struct in CreateInfo or via env var
    (LIBXGL_LAYER_LIBS)
diff --git a/layers/basic_plugin.c b/layers/basic_plugin.c
index 3807d493..1674107d 100644
--- a/layers/basic_plugin.c
+++ b/layers/basic_plugin.c
@@ -144,7 +144,7 @@ XGL_LAYER_EXPORT XGL_RESULT XGLAPI xglGetGpuInfo(XGL_PHYSICAL_GPU gpu, XGL_PHYSI
     XGL_BASE_LAYER_OBJECT* gpuw = (XGL_BASE_LAYER_OBJECT *) gpu;
     printf("At start of wrapped xglGetGpuInfo() call w/ gpu: %p\n", (void*)gpu);
     pCurObj = gpuw;
-    pthread_once(&tabOnce, initLayerTable);
+    pthread_once(&tabOnce, initLayerTable);  //Required for LD_PRELOAD case
     XGL_RESULT result = myTable.GetGpuInfo((XGL_PHYSICAL_GPU)gpuw->nextObject, infoType, pDataSize, pData);
     printf("Completed wrapped xglGetGpuInfo() call w/ gpu: %p\n", (void*)gpu);
     return result;
@@ -155,7 +155,7 @@ XGL_LAYER_EXPORT XGL_RESULT XGLAPI xglCreateDevice(XGL_PHYSICAL_GPU gpu, const X
     XGL_BASE_LAYER_OBJECT* gpuw = (XGL_BASE_LAYER_OBJECT *) gpu;
     printf("At start of wrapped xglCreateDevice() call w/ gpu: %p\n", (void*)gpu);
     pCurObj = gpuw;
-    pthread_once(&tabOnce, initLayerTable); 
+    pthread_once(&tabOnce, initLayerTable);   //Required for LD_PRELOAD case
     XGL_RESULT result = myTable.CreateDevice((XGL_PHYSICAL_GPU)gpuw->nextObject, pCreateInfo, pDevice);
     printf("Completed wrapped xglCreateDevice() call w/ pDevice: %p\n", (void*)pDevice);
     return result;