    /* SPDX-License-Identifier: MIT */
    /******************************************************************************
     * vscsiif.h
     *
     * Based on the blkif.h code.
     *
     * Copyright(c) FUJITSU Limited 2008.
     */

    #ifndef __XEN__PUBLIC_IO_SCSI_H__
    #define __XEN__PUBLIC_IO_SCSI_H__

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

    /*
     * Feature and Parameter Negotiation
     * =================================
     * The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
     * communicate capabilities and to negotiate operating parameters.  This
     * section enumerates these nodes which reside in the respective front and
     * backend portions of the XenStore, following the XenBus convention.
     *
     * Any specified default value is in effect if the corresponding XenBus node
     * is not present in the XenStore.
     *
     * XenStore nodes in sections marked "PRIVATE" are solely for use by the
     * driver side whose XenBus tree contains them.
     *
     *****************************************************************************
     *                            Backend XenBus Nodes
     *****************************************************************************
     *
     *------------------ Backend Device Identification (PRIVATE) ------------------
     *
     * p-devname
     *      Values:         string
     *
     *      A free string used to identify the physical device (e.g. a disk name).
     *
     * p-dev
     *      Values:         string
     *
     *      A string specifying the backend device: either a 4-tuple "h:c:t:l"
     *      (host, controller, target, lun, all integers), or a WWN (e.g.
     *      "naa.60014054ac780582:0").
     *
     * v-dev
     *      Values:         string
     *
     *      A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
     *      (host, controller, target, lun, all integers).
     *
     *--------------------------------- Features ---------------------------------
     *
     * feature-sg-grant
     *      Values:         unsigned [VSCSIIF_SG_TABLESIZE...65535]
     *      Default Value:  0
     *
     *      Specifies the maximum number of scatter/gather elements in grant pages
     *      supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
     *      SG elements specified directly in the request.
     *
     *****************************************************************************
     *                            Frontend XenBus Nodes
     *****************************************************************************
     *
     *----------------------- Request Transport Parameters -----------------------
     *
     * event-channel
     *      Values:         unsigned
     *
     *      The identifier of the Xen event channel used to signal activity
     *      in the ring buffer.
     *
     * ring-ref
     *      Values:         unsigned
     *
     *      The Xen grant reference granting permission for the backend to map
     *      the sole page in a single page sized ring buffer.
     *
     * protocol
     *      Values:         string (XEN_IO_PROTO_ABI_*)
     *      Default Value:  XEN_IO_PROTO_ABI_NATIVE
     *
     *      The machine ABI rules governing the format of all ring request and
     *      response structures.
     */

    /*
     * Xenstore format in practice
     * ===========================
     *
     * The backend driver uses a single_host:many_devices notation to manage domU
     * devices. Everything is stored in /local/domain/<backend_domid>/backend/vscsi/.
     * The xenstore layout looks like this (dom0 is assumed to be the backend_domid):
     *
     *     <domid>/<vhost>/feature-host = "0"
     *     <domid>/<vhost>/frontend = "/local/domain/<domid>/device/vscsi/0"
     *     <domid>/<vhost>/frontend-id = "<domid>"
     *     <domid>/<vhost>/online = "1"
     *     <domid>/<vhost>/state = "4"
     *     <domid>/<vhost>/vscsi-devs/dev-0/p-dev = "8:0:2:1" or "naa.wwn:lun"
     *     <domid>/<vhost>/vscsi-devs/dev-0/state = "4"
     *     <domid>/<vhost>/vscsi-devs/dev-0/v-dev = "0:0:0:0"
     *     <domid>/<vhost>/vscsi-devs/dev-1/p-dev = "8:0:2:2"
     *     <domid>/<vhost>/vscsi-devs/dev-1/state = "4"
     *     <domid>/<vhost>/vscsi-devs/dev-1/v-dev = "0:0:1:0"
     *
     * The frontend driver maintains its state in
     * /local/domain/<domid>/device/vscsi/.
     *
     *     <vhost>/backend = "/local/domain/0/backend/vscsi/<domid>/<vhost>"
     *     <vhost>/backend-id = "0"
     *     <vhost>/event-channel = "20"
     *     <vhost>/ring-ref = "43"
     *     <vhost>/state = "4"
     *     <vhost>/vscsi-devs/dev-0/state = "4"
     *     <vhost>/vscsi-devs/dev-1/state = "4"
     *
     * In addition to the entries for backend and frontend these flags are stored
     * for the toolstack:
     *
     *     <domid>/<vhost>/vscsi-devs/dev-1/p-devname = "/dev/$device"
     *     <domid>/<vhost>/libxl_ctrl_index = "0"
     *
     *
     * Backend/frontend protocol
     * =========================
     *
     * To create a vhost along with a device:
     *     <domid>/<vhost>/feature-host = "0"
     *     <domid>/<vhost>/frontend = "/local/domain/<domid>/device/vscsi/0"
     *     <domid>/<vhost>/frontend-id = "<domid>"
     *     <domid>/<vhost>/online = "1"
     *     <domid>/<vhost>/state = "1"
     *     <domid>/<vhost>/vscsi-devs/dev-0/p-dev = "8:0:2:1"
     *     <domid>/<vhost>/vscsi-devs/dev-0/state = "1"
     *     <domid>/<vhost>/vscsi-devs/dev-0/v-dev = "0:0:0:0"
     * Wait for <domid>/<vhost>/state + <domid>/<vhost>/vscsi-devs/dev-0/state become 4
     *
     * To add another device to a vhost:
     *     <domid>/<vhost>/state = "7"
     *     <domid>/<vhost>/vscsi-devs/dev-1/p-dev = "8:0:2:2"
     *     <domid>/<vhost>/vscsi-devs/dev-1/state = "1"
     *     <domid>/<vhost>/vscsi-devs/dev-1/v-dev = "0:0:1:0"
     * Wait for <domid>/<vhost>/state + <domid>/<vhost>/vscsi-devs/dev-1/state become 4
     *
     * To remove a device from a vhost:
     *     <domid>/<vhost>/state = "7"
     *     <domid>/<vhost>/vscsi-devs/dev-1/state = "5"
     * Wait for <domid>/<vhost>/state to become 4
     * Wait for <domid>/<vhost>/vscsi-devs/dev-1/state become 6
     * Remove <domid>/<vhost>/vscsi-devs/dev-1/{state,p-dev,v-dev,p-devname}
     * Remove <domid>/<vhost>/vscsi-devs/dev-1/
     *
     */

    /* Requests from the frontend to the backend */

    /*
     * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
     * The target is specified via channel, id and lun.
     *
     * The operation to be performed is specified via a CDB in cmnd[], the length
     * of the CDB is in cmd_len. sc_data_direction specifies the direction of data
     * (to the device, from the device, or none at all).
     *
     * If data is to be transferred to or from the device the buffer(s) in the
     * guest memory is/are specified via one or multiple scsiif_request_segment
     * descriptors each specifying a memory page via a grant_ref_t, a offset into
     * the page and the length of the area in that page. All scsiif_request_segment
     * areas concatenated form the resulting data buffer used by the operation.
     * If the number of scsiif_request_segment areas is not too large (less than
     * or equal VSCSIIF_SG_TABLESIZE) the areas can be specified directly in the
     * seg[] array and the number of valid scsiif_request_segment elements is to be
     * set in nr_segments.
     *
     * If "feature-sg-grant" in the Xenstore is set it is possible to specify more
     * than VSCSIIF_SG_TABLESIZE scsiif_request_segment elements via indirection.
     * The maximum number of allowed scsiif_request_segment elements is the value
     * of the "feature-sg-grant" entry from Xenstore. When using indirection the
     * seg[] array doesn't contain specifications of the data buffers, but
     * references to scsiif_request_segment arrays, which in turn reference the
     * data buffers. While nr_segments holds the number of populated seg[] entries
     * (plus the set VSCSIIF_SG_GRANT bit), the number of scsiif_request_segment
     * elements referencing the target data buffers is calculated from the lengths
     * of the seg[] elements (the sum of all valid seg[].length divided by the
     * size of one scsiif_request_segment structure). The frontend may use a mix of
     * direct and indirect requests.
     */
    #define VSCSIIF_ACT_SCSI_CDB         1

    /*
     * Request abort of a running operation for the specified target given by
     * channel, id, lun and the operation's rqid in ref_rqid.
     */
    #define VSCSIIF_ACT_SCSI_ABORT       2

    /*
     * Request a device reset of the specified target (channel and id).
     */
    #define VSCSIIF_ACT_SCSI_RESET       3

    /*
     * Preset scatter/gather elements for a following request. Deprecated.
     * Keeping the define only to avoid usage of the value "4" for other actions.
     */
    #define VSCSIIF_ACT_SCSI_SG_PRESET   4

    /*
     * Maximum scatter/gather segments per request.
     *
     * Considering balance between allocating at least 16 "vscsiif_request"
     * structures on one page (4096 bytes) and the number of scatter/gather
     * elements needed, we decided to use 26 as a magic number.
     *
     * If "feature-sg-grant" is set, more scatter/gather elements can be specified
     * by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
     * In this case the vscsiif_request seg elements don't contain references to
     * the user data, but to the SG elements referencing the user data.
     */
    #define VSCSIIF_SG_TABLESIZE             26

    /*
     * based on Linux kernel 2.6.18, still valid
     *
     * Changing these values requires support of multiple protocols via the rings
     * as "old clients" will blindly use these values and the resulting structure
     * sizes.
     */
    #define VSCSIIF_MAX_COMMAND_SIZE         16
    #define VSCSIIF_SENSE_BUFFERSIZE         96
    #define VSCSIIF_PAGE_SIZE              4096

    struct scsiif_request_segment {
        grant_ref_t gref;
        uint16_t offset;
        uint16_t length;
    };
    typedef struct scsiif_request_segment vscsiif_segment_t;

    #define VSCSIIF_SG_PER_PAGE (VSCSIIF_PAGE_SIZE / sizeof(struct scsiif_request_segment))

    /* Size of one request is 252 bytes */
    struct vscsiif_request {
        uint16_t rqid;          /* private guest value, echoed in resp  */
        uint8_t act;            /* command between backend and frontend */
        uint8_t cmd_len;        /* valid CDB bytes */

        uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE]; /* the CDB */
        uint16_t timeout_per_command;   /* deprecated: timeout in secs, 0=default */
        uint16_t channel, id, lun;      /* (virtual) device specification */
        uint16_t ref_rqid;              /* command abort reference */
        uint8_t sc_data_direction;      /* for DMA_TO_DEVICE(1)
                                           DMA_FROM_DEVICE(2)
                                           DMA_NONE(3) requests  */
        uint8_t nr_segments;            /* Number of pieces of scatter-gather */
    /*
     * flag in nr_segments: SG elements via grant page
     *
     * If VSCSIIF_SG_GRANT is set, the low 7 bits of nr_segments specify the number
     * of grant pages containing SG elements. Usable if "feature-sg-grant" set.
     */
    #define VSCSIIF_SG_GRANT    0x80

        vscsiif_segment_t seg[VSCSIIF_SG_TABLESIZE];
        uint32_t reserved[3];
    };
    typedef struct vscsiif_request vscsiif_request_t;

    /*
     * The following interface is deprecated!
     */
    #define VSCSIIF_SG_LIST_SIZE ((sizeof(vscsiif_request_t) - 4) \
                                  / sizeof(vscsiif_segment_t))

    struct vscsiif_sg_list {
        /* First two fields must match struct vscsiif_request! */
        uint16_t rqid;          /* private guest value, must match main req */
        uint8_t act;            /* VSCSIIF_ACT_SCSI_SG_PRESET */
        uint8_t nr_segments;    /* Number of pieces of scatter-gather */
        vscsiif_segment_t seg[VSCSIIF_SG_LIST_SIZE];
    };
    typedef struct vscsiif_sg_list vscsiif_sg_list_t;
    /* End of deprecated interface */

    /* Size of one response is 252 bytes */
    struct vscsiif_response {
        uint16_t rqid;          /* identifies request */
        uint8_t act;            /* deprecated: valid only if SG_PRESET supported */
        uint8_t sense_len;
        uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
        int32_t rslt;
        uint32_t residual_len;     /* request bufflen -
                                      return the value from physical device */
        uint32_t reserved[36];
    };
    typedef struct vscsiif_response vscsiif_response_t;

    /* SCSI I/O status from vscsiif_response->rslt */
    #define XEN_VSCSIIF_RSLT_STATUS(x)  ((x) & 0x00ff)

    /* Host I/O status from vscsiif_response->rslt */
    #define XEN_VSCSIIF_RSLT_HOST(x)    (((x) & 0x00ff0000) >> 16)
    #define XEN_VSCSIIF_RSLT_HOST_OK                   0
    /* Couldn't connect before timeout */
    #define XEN_VSCSIIF_RSLT_HOST_NO_CONNECT           1
    /* Bus busy through timeout */
    #define XEN_VSCSIIF_RSLT_HOST_BUS_BUSY             2
    /* Timed out for other reason */
    #define XEN_VSCSIIF_RSLT_HOST_TIME_OUT             3
    /* Bad target */
    #define XEN_VSCSIIF_RSLT_HOST_BAD_TARGET           4
    /* Abort for some other reason */
    #define XEN_VSCSIIF_RSLT_HOST_ABORT                5
    /* Parity error */
    #define XEN_VSCSIIF_RSLT_HOST_PARITY               6
    /* Internal error */
    #define XEN_VSCSIIF_RSLT_HOST_ERROR                7
    /* Reset by somebody */
    #define XEN_VSCSIIF_RSLT_HOST_RESET                8
    /* Unexpected interrupt */
    #define XEN_VSCSIIF_RSLT_HOST_BAD_INTR             9
    /* Force command past mid-layer */
    #define XEN_VSCSIIF_RSLT_HOST_PASSTHROUGH         10
    /* Retry requested */
    #define XEN_VSCSIIF_RSLT_HOST_SOFT_ERROR          11
    /* Hidden retry requested */
    #define XEN_VSCSIIF_RSLT_HOST_IMM_RETRY           12
    /* Requeue command requested */
    #define XEN_VSCSIIF_RSLT_HOST_REQUEUE             13
    /* Transport error disrupted I/O */
    #define XEN_VSCSIIF_RSLT_HOST_TRANSPORT_DISRUPTED 14
    /* Transport class fastfailed */
    #define XEN_VSCSIIF_RSLT_HOST_TRANSPORT_FAILFAST  15
    /* Permanent target failure */
    #define XEN_VSCSIIF_RSLT_HOST_TARGET_FAILURE      16
    /* Permanent nexus failure on path */
    #define XEN_VSCSIIF_RSLT_HOST_NEXUS_FAILURE       17
    /* Space allocation on device failed */
    #define XEN_VSCSIIF_RSLT_HOST_ALLOC_FAILURE       18
    /* Medium error */
    #define XEN_VSCSIIF_RSLT_HOST_MEDIUM_ERROR        19
    /* Transport marginal errors */
    #define XEN_VSCSIIF_RSLT_HOST_TRANSPORT_MARGINAL  20

    /* Result values of reset operations */
    #define XEN_VSCSIIF_RSLT_RESET_SUCCESS  0x2002
    #define XEN_VSCSIIF_RSLT_RESET_FAILED   0x2003

    DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);

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