clGetDeviceIDs fails when passed CL_DEVICE_TYPE_ALL

Hello,

When I call clGetDeviceIDs with CL_DEVICE_TYPE_ALL, it fails with CL_INVALID_DEVICE_TYPE, why?

It works fine when I pass CL_DEVICE_TYPE_ACCELERATOR, but shouldn't it work with CL_DEVICE_TYPE_ALL as well since its intended purpose is to return ALL devices?

Thanks.