FreeBSD/Linux Kernel Cross Reference
sys/xen/interface/io/vscsiif.h

     /******************************************************************************
      * vscsiif.h
      *
      * Based on the blkif.h code.
      *
      * Permission is hereby granted, free of charge, to any person obtaining a copy
      * of this software and associated documentation files (the "Software"), to
      * deal in the Software without restriction, including without limitation the
      * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
     * sell copies of the Software, and to permit persons to whom the Software is
     * furnished to do so, subject to the following conditions:
     *
     * The above copyright notice and this permission notice shall be included in
     * all copies or substantial portions of the Software.
     *
     * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
     * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
     * DEALINGS IN THE SOFTWARE.
     *
     * 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 = ""
    *     <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 = ""
    *     <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 = ""
    *
    *
    * Backend/frontend protocol
    * =========================
    *
    * To create a vhost along with a device:
    *     <domid>/<vhost>/feature-host = ""
    *     <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;
   
   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:
    */

Cache object: 6289051261299bf2523fd9da68143bcc