NVMe

It is recommended that you become familiar with the mechanics of the Core API before diving into the NVMe specifics. Regardless, here is a brief over of the NVMe portion of the xNVMe API.

Command-Sets

The command-capabilities of NVMe devices are grouped in defitions of command-sets, these are representated in xNVMe in the following modules:

NVM (libxnvme_nvm.h)

This describes collections of NAND memory as a range of logical block addresses, with commands to read and write them. This is first set of commands provided with NVMe and supports the well-known use-case of block-storage.

ZNS (libxnvme_znd.h)

This an extension / alternate block-storage model, where NAND memory is still organized as a range of logical blocks, but furthermore arranged in zones. To work with zones, then one needs to query device of their sizes, state, and reset it when needed. And adhere to I/O constraints. Helpers for all this is provided in the API.

KVS (libxnvme_kvs.h)

This describes colletcions of NAND memory as Key-Value pairs, thus commands for KVS are insert/retrieve rather than write/read. Additional commands are needed to list and delete. These are provided here.

ADMIN (libxnvme_adm.h)

Lastly, general admin commands are provided, these include identify commands, these provide data on controllers, namespaces, both in a general form and in command-set specific versions. Getting log-pages, getting/setting features are also admin commands. These and more are providede in the admin portion of the API.

Specification Definitions

libxnvme_spec.h is a C representation of the NVMe specification. This includes most of the structures described across the base, NVM, ZNS, and KV specifications.

In line with this, libxnvme_pi.h and libxnvme_topology.h provides functions for NVMe operations which are not commands. libxnvme_pi.h has functions for generating and verifying protection info. libxnvme_topology.h has functions for subsystem (or controller) reset, namespace rescan, and getting controller registers.