Subject: operation not supported ...
To: None <>
From: Paul Kranenburg <>
List: tech-kern
Date: 12/20/1993 09:41:50
There are several spots in the current kernel sources where functions
return the error code EOPNOTSUPP to apparently signal the fact that
the requested operation is somehow "not supported".

Now, the EOPNOTSUPP code is classified as an "ipc/network argument error", and
the verbose message that goes with it is: "Operation not supported on socket".

Quite a few routines now returning EOPNOTSUPP have actually nothing to do
with sockets and one would expect them to simply say "Operation not
supported by device", ie. ENODEV.

May be there is a swing towards generalizing the use of EOPNOTSUPP to mean
"Operation not supported whether device or socket or anything else", but for
the moment I'm inclined to believe that it is the result of a poorly chosen
mnemonic for a particular class of (network) errors. Perhaps it's time to
weed through the sources and reconsider each dubious instance of this
return value.