What does errno 55 (EBADSLT) mean?

EBADSLT

The word “slot” needs the producer’s data model

EBADSLT is value 55 in the Solaris/illumos historical convergent-error range. The official errno catalog names an invalid slot but does not define a universal Solaris structure or modern syscall slot associated with this error. POSIX Issue 8 has no EBADSLT entry.

Consequently, a debugger cannot infer whether “slot” means an array entry, exchange slot, device channel, or private protocol field from errno alone. The old custom page incorrectly treated all values in this range as one generic exchange failure; the useful distinction here is that the producer rejected a slot selection.

How to make the error actionable

• Log the selected slot/index value and the bounds or table version used by the originating interface.
• Check for stale ABI assumptions when ported code shares structures with a driver or compatibility module.
• Do not substitute advice for filesystem, sockets, or scheduler “slots” unless the failing API documents that meaning.

References

• Oracle Solaris intro(2) errno catalog
• illumos sys/errno.h ABI definitions
• POSIX Issue 8 errno.h

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