The error -1 is actually ERESTART in the context of syscall. It is for kernel mode only and will not be passed to user mode. When the kernel sees this error it will restart the syscall. When the the SFP module data is not available, e.g. the SFP module is not present, the ioctl handler returns ERESTART and kernel will retry infinitely, hence the userland `ifconfig -v ql0` will hang forever until get interrupted. That is apparently wrong. Fix that by returning error ENODEV to indicate the SFP module data is not available. As for the case that ecore_ptt_acquire() fails, it appears to be quite safe to restart, so keep returning ERESTART. Reported by: Steve Wheeler See also: https://redmine.pfsense.org/issues/16248 Reviewed by: kbowling MFC after: 3 days Differential Revision: https://reviews.freebsd.org/D51351