[Question] Usage of ENOTSUPP error code

[Masahiro Yamada]

Hello experts,


I noticed many drivers return -ENOTSUPP on error.



I assume ENOTSUPP is defined in include/linux/errno.h
as follows:


/* Defined for the NFSv3 protocol */
#define EBADHANDLE 521 /* Illegal NFS file handle */
#define ENOTSYNC 522 /* Update synchronization mismatch */
#define EBADCOOKIE 523 /* Cookie is stale */
#define ENOTSUPP 524 /* Operation is not supported */
#define ETOOSMALL 525 /* Buffer or request is too small */
#define ESERVERFAULT 526 /* An untranslatable error occurred */
#define EBADTYPE 527 /* Type not supported by server */
#define EJUKEBOX 528 /* Request initiated, but will not complete
before timeout */
#define EIOCBQUEUED 529 /* iocb queued, will get completion event */


I also assume the comment "Defined for the NFSv3 protocol"
is valid for whole of this block.

If so, should ENOTSUPP be only used for NFS-related errors?

In fact, ENOTSUPP is used by various drivers
including non-network ones such as pinctrl, USB, etc.





-- 
Best Regards
Masahiro Yamada
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