Supported an OPENCL_VISIBLE_DEVICES environment variable inspired from CUDA_VISIBLE_DEVICES.

OPENCL_VISIBLE_DEVICES=descriptor_list
descriptor_list -> descriptor | descriptor::descriptor_list
descriptor -> driver,platform | driver,platform,type | driver,platform,type,device_list
device_list -> device_id | device_id,device_list
driver: client driver (foo.icd or foo.so)
platform: platform ID
type: gpu, cpu, accelerator, custom, or any
device_id: device ID in the platform

This patch is to land KhronosGroup#45 again.
Most of the code is from pull request 45.

e.g., OPENCL_VISIBLE_DEVICES=foo.icd,0,gpu,0,1::bar.icd,1,cpu,0 only shows
- GPU 0, 1 in the first platform of foo.icd
- CPU 0 in the second platform of bar.icd

Author: cdai2

CMakeLists.txt

@@ -54,6 +54,7 @@ set (OPENCL_ICD_LOADER_SOURCES
     loader/icd_dispatch.h
     loader/icd_dispatch_generated.c
     loader/icd_envvars.h
+    loader/icd_envvars.c
     loader/icd_platform.h)
 
 if (WIN32)

loader/icd.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016-2020 The Khronos Group Inc.
+ * Copyright (c) 2016-2021 The Khronos Group Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -33,6 +33,7 @@ struct KHRLayer *khrFirstLayer = NULL;
 // entrypoint to initialize the ICD and add all vendors
 void khrIcdInitialize(void)
 {
+    khrIcdOsGetOpenCLVisibleDevicesOnce();
     // enumerate vendors present on the system
     khrIcdOsVendorsEnumerateOnce();
 }
@@ -122,6 +123,12 @@ void khrIcdVendorAdd(const char *libraryName)
         {
             continue;
         }
+
+        if (!khrIcdCheckPlatformVisible(libraryName, i))
+        {
+            continue;
+        }
+
         result = platforms[i]->dispatch->clGetPlatformInfo(
             platforms[i],
             CL_PLATFORM_ICD_SUFFIX_KHR,
@@ -179,8 +186,9 @@ void khrIcdVendorAdd(const char *libraryName)
             *prevNextPointer = vendor;
         }
 
-        KHR_ICD_TRACE("successfully added vendor %s with suffix %s\n", libraryName, suffix);
+        khrIcdVisibilitySetPlatform(libraryName, i, platforms[i]);
 
+        KHR_ICD_TRACE("successfully added vendor %s with suffix %s\n", libraryName, suffix);
     }
 
 Done:

loader/icd_dispatch_generated.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2012-2020 The Khronos Group Inc.
+ * Copyright (c) 2012-2021 The Khronos Group Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,6 +17,7 @@
  */
 
 #include "icd_dispatch.h"
+#include "icd_envvars.h"
 #include "icd.h"
 
 #ifdef __cplusplus
@@ -96,12 +97,81 @@ CL_API_ENTRY cl_int CL_API_CALL clGetDeviceIDs(
             num_devices);
 #endif // defined(CL_ENABLE_LAYERS)
     KHR_ICD_VALIDATE_HANDLE_RETURN_ERROR(platform, CL_INVALID_PLATFORM);
-    return platform->dispatch->clGetDeviceIDs(
+    cl_uint num_all_devices = 0;
+    cl_device_id *all_devices = NULL;
+    cl_uint i;
+    cl_int result;
+
+    if (!num_entries && devices)
+    {
+        return CL_INVALID_VALUE;
+    }
+    if (!devices && !num_devices)
+    {
+        return CL_INVALID_VALUE;
+    }
+
+    if (num_devices)
+    {
+        *num_devices = 0;
+    }
+    for (i = 0; i < num_entries && devices; ++i)
+    {
+        devices[i] = NULL;
+    }
+
+
+    result = platform->dispatch->clGetDeviceIDs(
         platform,
         device_type,
-        num_entries,
-        devices,
-        num_devices);
+        0,
+        NULL,
+        &num_all_devices);
+
+    if (CL_SUCCESS != result)
+    {
+        return result;
+    }
+    if (!num_all_devices)
+    {
+        return CL_DEVICE_NOT_FOUND;
+    }
+    all_devices = (cl_device_id*)malloc(sizeof(cl_device_id) * num_all_devices);
+    if (!all_devices)
+    {
+        return CL_OUT_OF_HOST_MEMORY;
+    }
+    result = platform->dispatch->clGetDeviceIDs(
+        platform,
+        device_type,
+        num_all_devices,
+        all_devices,
+        NULL);
+    if (CL_SUCCESS != result)
+    {
+        free(all_devices);
+        return result;
+    }
+
+    result = CL_DEVICE_NOT_FOUND;
+    for (i = 0; i < num_all_devices; ++i)
+    {
+        if (khrIcdCheckDeviceVisible(platform, all_devices[i]))
+        {
+            result = CL_SUCCESS;
+            if (num_entries && devices)
+            {
+                *(devices++) = all_devices[i];
+                --num_entries;
+            }
+            if (num_devices)
+            {
+                ++(*num_devices);
+            }
+        }
+    }
+    free(all_devices);
+    return result;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -235,6 +305,12 @@ CL_API_ENTRY cl_context CL_API_CALL clCreateContextFromType(
     void* user_data,
     cl_int* errcode_ret)
 {
+    cl_platform_id platform = NULL;
+    cl_uint num_devices = 0;
+    cl_device_id *devices = NULL;
+    cl_context context = NULL;
+    cl_int result;
+
     khrIcdInitialize();
 #if defined(CL_ENABLE_LAYERS)
     if (khrFirstLayer)
@@ -245,15 +321,56 @@ CL_API_ENTRY cl_context CL_API_CALL clCreateContextFromType(
             user_data,
             errcode_ret);
 #endif // defined(CL_ENABLE_LAYERS)
-    cl_platform_id platform = NULL;
     khrIcdContextPropertiesGetPlatform(properties, &platform);
     KHR_ICD_VALIDATE_HANDLE_RETURN_HANDLE(platform, CL_INVALID_PLATFORM);
-    return platform->dispatch->clCreateContextFromType(
+
+    result = clGetDeviceIDs(platform, device_type, 0, NULL, &num_devices);
+    if (CL_SUCCESS != result)
+    {
+        if (*errcode_ret)
+        {
+            *errcode_ret = result;
+        }
+        return NULL;
+    }
+    if (!num_devices)
+    {
+        if (*errcode_ret)
+        {
+            *errcode_ret = CL_DEVICE_NOT_FOUND;
+        }
+        return NULL;
+    }
+    devices = (cl_device_id*)malloc(sizeof(cl_device_id) * num_devices);
+    if (!devices)
+    {
+        if (*errcode_ret)
+        {
+            *errcode_ret = CL_OUT_OF_HOST_MEMORY;
+        }
+        return NULL;
+    }
+    result = clGetDeviceIDs(platform, device_type, num_devices, devices, NULL);
+    if (CL_SUCCESS != result)
+    {
+        free(devices);
+        if (*errcode_ret)
+        {
+            *errcode_ret = result;
+        }
+        return NULL;
+    }
+
+    context = platform->dispatch->clCreateContext(
         properties,
-        device_type,
+        num_devices,
+        devices,
         pfn_notify,
         user_data,
         errcode_ret);
+    free(devices);
+    return context;
+
 }
 
 ///////////////////////////////////////////////////////////////////////////////