add comment clarifying the cusolver_enabled flag
@@ -9,6 +9,8 @@ from cupy.cuda cimport runtime
from cupy.cuda import runtime as runtime_module
from cupy import util
+# This flag is kept for backward compatibility.
+# It is always True as cuSOLVER library is always available in CUDA 8.0+.
cusolver_enabled = True
cdef object _thread_local = threading.local()
