/******************************************************************************
 * blkif.h
 * 
 * Unified block-device I/O interface for Xen guest OSes.
 * 
 * Copyright (c) 2003-2004, Keir Fraser
 */

#ifndef __XEN_PUBLIC_IO_BLKIF_H__
#define __XEN_PUBLIC_IO_BLKIF_H__

#include "ring.h"
#include "../grant_table.h"

/*
 * Front->back notifications: When enqueuing a new request, sending a
 * notification can be made conditional on req_event (i.e., the generic
 * hold-off mechanism provided by the ring macros). Backends must set
 * req_event appropriately (e.g., using RING_FINAL_CHECK_FOR_REQUESTS()).
 * 
 * Back->front notifications: When enqueuing a new response, sending a
 * notification can be made conditional on rsp_event (i.e., the generic
 * hold-off mechanism provided by the ring macros). Frontends must set
 * rsp_event appropriately (e.g., using RING_FINAL_CHECK_FOR_RESPONSES()).
 */

#ifndef blkif_vdev_t
#define blkif_vdev_t   uint16_t
#endif
#define blkif_sector_t uint64_t

#define BLKIF_OP_READ      0
#define BLKIF_OP_WRITE     1

/*
 * Maximum scatter/gather segments per request.
 * This is carefully chosen so that sizeof(blkif_ring_t) <= PAGE_SIZE.
 * NB. This could be 12 if the ring indexes weren't stored in the same page.
 */
#define BLKIF_MAX_SEGMENTS_PER_REQUEST 11

struct blkif_request_segment {
    grant_ref_t gref;        /* reference to I/O buffer frame        */
    /* @first_sect: first sector in frame to transfer (inclusive).   */
    /* @last_sect: last sector in frame to transfer (inclusive).     */
    uint8_t     first_sect, last_sect;
};

struct blkif_request {
    uint8_t        operation;    /* BLKIF_OP_???                         */
    uint8_t        nr_segments;  /* number of segments                   */
    blkif_vdev_t   handle;       /* only for read/write requests         */
    uint64_t       id;           /* private guest value, echoed in resp  */
    blkif_sector_t sector_number;/* start sector idx on disk (r/w only)  */
    struct blkif_request_segment seg[BLKIF_MAX_SEGMENTS_PER_REQUEST];
};
typedef struct blkif_request blkif_request_t;

struct blkif_response {
    uint64_t        id;              /* copied from request */
    uint8_t         operation;       /* copied from request */
    int16_t         status;          /* BLKIF_RSP_???       */
};
typedef struct blkif_response blkif_response_t;

#define BLKIF_RSP_ERROR  -1 /* non-specific 'error' */
#define BLKIF_RSP_OKAY    0 /* non-specific 'okay'  */

/*
 * Generate blkif ring structures and types.
 */

DEFINE_RING_TYPES(blkif, struct blkif_request, struct blkif_response);

#define VDISK_CDROM        0x1
#define VDISK_REMOVABLE    0x2
#define VDISK_READONLY     0x4

#endif /* __XEN_PUBLIC_IO_BLKIF_H__ */

/*
 * Local variables:
 * mode: C
 * c-set-style: "BSD"
 * c-basic-offset: 4
 * tab-width: 4
 * indent-tabs-mode: nil
 * End:
 */