io_uring.h (documented), finally

io_uring.h

struct io_sqring_offsets {
	__u32 head; /* offset of ring head */
	__u32 tail; /* offset of ring tail */
	__u32 ring_mask; /* ring mask value */
	__u32 ring_entries; /* entries in ring */
	__u32 flags; /* ring flags */
	__u32 dropped; /* number of sqes not submitted */
	__u32 array; /* sqe index array */
	__u32 resv1;
	__u64 resv2;
};

struct io_cqring_offsets {
	__u32 head;
	__u32 tail;
	__u32 ring_mask;
	__u32 ring_entries;
	__u32 overflow;
	__u32 cqes;
	__u32 flags;
	__u32 resv1;
	__u64 user_addr;
};

struct io_uring_params {
	__u32 sq_entries; /* filled by kernel, how many sqe entries this ring supports */
	__u32 cq_entries; /* this field tell how big cq_ring */ 
	__u32 flags;
	__u32 sq_thread_cpu;
	__u32 sq_thread_idle;
	__u32 features;  /* if this field filled with 
			    IORING_FEAT_SINGLE_MMAP, we can do second mmap() */ 
	__u32 wq_fd;
	__u32 resv[3];
	struct io_sqring_offsets sq_off; /* sq_off and cq_off are essential for setup offset */
	struct io_cqring_offsets cq_off;
};


-------- submission struct ------------
struct io_uring_sqe {
        __u8 opcode;    /* type of operation for this sqe */
        __u8 flags;     /* IOSQE_ flags */
        __u16 ioprio;   /* ioprio for the request */
        __s32 fd;       /* file descriptor to do IO on */
        __u64 off;      /* offset into file */
        __u64 addr;     /* addr contains the address at which 
                        the operation should perform IO, 
                        if the op-code describes an operation that 
                        transfers data. If the operation is a vectored
                        read/write of some sort, this will be a pointer 
                        to an struct iovec array, as used by preadv(2), for
                        example. For a non-vectored IO transfer,
                        addr must contain the address directly */
        __u32 len;      /* This carries into len, which is either 
        		a byte count for a non-vectored IO transfer, 
        		or a number of vectors described by
                        addr for a vectored IO transfer
                        */
        union {
                __kernel_rwf_t rw_flags; /* Next follows a union of 
                                        flags that are specific to the op-code */
                __u32 fsync_flags;
                __u16 poll_events;
                __u32 sync_range_flags;
                __u32 msg_flags;
        };
        __u64 user_data;                /* untouched by the kernel */
        union {
                __u16 buf_index; /* buf_index will be described
                                in the advanced use cases section */
                __u64 __pad2[3]; /* unused, for future and padding in 64 */
        };
};

--------- completion struct -------------
struct io_uring_cqe {
	__u64	user_data;	/* sqe->data submission passed back */
	__s32	res;		/* result code for this event */
	__u32	flags;

	/*
	 * If the ring is initialized with IORING_SETUP_CQE32, then this field
	 * contains 16-bytes of padding, doubling the size of the CQE.
	 */
	__u64 big_cqe[];
};




------- opcode list ----------------
enum io_uring_op {
	IORING_OP_NOP,
	IORING_OP_READV,
	IORING_OP_WRITEV,
	IORING_OP_FSYNC,
	IORING_OP_READ_FIXED,
	IORING_OP_WRITE_FIXED,
	IORING_OP_POLL_ADD,
	IORING_OP_POLL_REMOVE,
	IORING_OP_SYNC_FILE_RANGE,
	IORING_OP_SENDMSG,
	IORING_OP_RECVMSG,
	IORING_OP_TIMEOUT,
	IORING_OP_TIMEOUT_REMOVE,
	IORING_OP_ACCEPT,
	IORING_OP_ASYNC_CANCEL,
	IORING_OP_LINK_TIMEOUT,
	IORING_OP_CONNECT,
	IORING_OP_FALLOCATE,
	IORING_OP_OPENAT,
	IORING_OP_CLOSE,
	IORING_OP_FILES_UPDATE,
	IORING_OP_STATX,
	IORING_OP_READ,
	IORING_OP_WRITE,
	IORING_OP_FADVISE,
	IORING_OP_MADVISE,
	IORING_OP_SEND,
	IORING_OP_RECV,
	IORING_OP_OPENAT2,
	IORING_OP_EPOLL_CTL,
	IORING_OP_SPLICE,
	IORING_OP_PROVIDE_BUFFERS,
	IORING_OP_REMOVE_BUFFERS,
	IORING_OP_TEE,
	IORING_OP_SHUTDOWN,
	IORING_OP_RENAMEAT,
	IORING_OP_UNLINKAT,
	IORING_OP_MKDIRAT,
	IORING_OP_SYMLINKAT,
	IORING_OP_LINKAT,
	IORING_OP_MSG_RING,
	IORING_OP_FSETXATTR,
	IORING_OP_SETXATTR,
	IORING_OP_FGETXATTR,
	IORING_OP_GETXATTR,
	IORING_OP_SOCKET,
	IORING_OP_URING_CMD,
	IORING_OP_SEND_ZC,
	IORING_OP_SENDMSG_ZC,
	IORING_OP_READ_MULTISHOT,
	IORING_OP_WAITID,
	IORING_OP_FUTEX_WAIT,
	IORING_OP_FUTEX_WAKE,
	IORING_OP_FUTEX_WAITV,
	IORING_OP_FIXED_FD_INSTALL,
	IORING_OP_FTRUNCATE,

	/* this goes last, obviously */
	IORING_OP_LAST,
};