Make people check their OpenCL driver

doc/doxygen/chapters/390_faq.doxy

@@ -226,4 +226,52 @@ starpu_resume();
 starpu_shutdown();
 \endcode
 
+\section OpenCLDrivers StarPU does not see my OpenCL device
+
+First make sure that your OpenCL is properly running outside StarPU: build and
+run the following program:
+
+\code{.c}
+#include <CL/cl.h>
+#include <stdio.h>
+#include <assert.h>
+
+int main(void) {
+    cl_device_id did[16];
+    cl_int err;
+    cl_platform_id pid, pids[16];
+    cl_uint nbplat, nb;
+    char buf[128];
+    size_t size;
+    int i, j;
+
+    err = clGetPlatformIDs(sizeof(pids)/sizeof(pids[0]), pids, &nbplat);
+    assert(err == CL_SUCCESS);
+    printf("%u platforms\n", nbplat);
+    for (j = 0; j < nbplat; j++) {
+        pid = pids[j];
+        printf("    platform %d\n", j);
+        err = clGetPlatformInfo(pid, CL_PLATFORM_VERSION, sizeof(buf)-1, buf, &size);
+        assert(err == CL_SUCCESS);
+        buf[size] = 0;
+        printf("        platform version %s\n", buf);
+
+        err = clGetDeviceIDs(pid, CL_DEVICE_TYPE_ALL, sizeof(did)/sizeof(did[0]), did, &nb);
+        assert(err == CL_SUCCESS);
+        printf("%d devices\n", nb);
+        for (i = 0; i < nb; i++) {
+            err = clGetDeviceInfo(did[i], CL_DEVICE_VERSION, sizeof(buf)-1, buf, &size);
+            buf[size] = 0;
+            printf("    device %d version %s\n", i, buf);
+        }
+    }
+
+    return 0;
+}
+\endcode
+
+If that program does not find your device, the problem is not at the StarPU
+level, but the OpenCL drivers, check the documentation of your OpenCL
+implementation.
+
 */