nvme_status_type - Man Page

enum nvme_status_type {
   NVME_STATUS_TYPE_SHIFT ,

   NVME_STATUS_TYPE_MASK ,

   NVME_STATUS_TYPE_NVME ,

   NVME_STATUS_TYPE_MI

};

NVME_STATUS_TYPE_SHIFT

shift value for status bits

NVME_STATUS_TYPE_MASK

mask value for status bits

NVME_STATUS_TYPE_NVME

NVMe command status value, typically from CDW3

NVME_STATUS_TYPE_MI

NVMe-MI header status

The nvme_* api returns an int, with negative values indicating an internal or syscall error, zero signifying success, positive values representing the NVMe status.

That latter case (the NVMe status) may represent status values from different parts of the transport/controller/etc, and are at most 16 bits of data. So, we use the most-significant 3 bits of the signed int to indicate which type of status this is.