Hi, all.
It's my first question in here and I'm newbie in kernel development.
I was curious when I saw that error codes are defined in macros
while success status is not expressed by macros.

For example, error codes are expressed by macros like this.
However, success is not defined but expressed by constant number.
Why don't we use a macro for success status for unity with fail status (error code)?
(I think that one of possible reasons are clarity of constant number (0)
or that success status is not always expressed by 0)

I tried to use similar macros such as SUCCESS or NO_ERROR,
but it seems that they are not defined in official mainline codes.

by default the return value 0 means ok. That is a general rule. So you can say this is an exception, there is no real need (to use a macro).

Thank you for the answer.
So it seems that using 'return 0;' is a general and traditional method, which make its meaning clear.