u64: " /* unsigned 64-bit value */ ", Modern versions of the Linux kernel are highly portable, running on numerous different architectures. Given the multiplatform nature of Linux, drivers intended for serious use should be portable as well. u64 is type int datatype with maximum possible size.
u64in:u64in helps you to share long urls across your multiple device in a click. On click of a button you will get an easily shareable qr-code ( and in upcoming versions a compressed url )