On FreeBSD this problem can be solved by '-W koi2dos' mount_msdos argument.
OpenBSD localhost 4.5 200908010004#0 i386 -- 4625
Sometimes I need to mount ${subject} or floppy disk where files have
cyrillic in own names. The problem is Midnight Commander unable to copy
such files from there. May be cause the char '?' present in file name.
