The Design and Implementation of the FreeBSD Operating System, Second Edition
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FreeBSD/Linux Kernel Cross Reference
sys/xen/interface/io/vscsiif.h

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    1 /******************************************************************************
    2  * vscsiif.h
    3  *
    4  * Based on the blkif.h code.
    5  *
    6  * Permission is hereby granted, free of charge, to any person obtaining a copy
    7  * of this software and associated documentation files (the "Software"), to
    8  * deal in the Software without restriction, including without limitation the
    9  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
   10  * sell copies of the Software, and to permit persons to whom the Software is
   11  * furnished to do so, subject to the following conditions:
   12  *
   13  * The above copyright notice and this permission notice shall be included in
   14  * all copies or substantial portions of the Software.
   15  *
   16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
   18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
   19  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
   20  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
   21  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
   22  * DEALINGS IN THE SOFTWARE.
   23  *
   24  * Copyright(c) FUJITSU Limited 2008.
   25  */
   26 
   27 #ifndef __XEN__PUBLIC_IO_SCSI_H__
   28 #define __XEN__PUBLIC_IO_SCSI_H__
   29 
   30 #include "ring.h"
   31 #include "../grant_table.h"
   32 
   33 /*
   34  * Feature and Parameter Negotiation
   35  * =================================
   36  * The two halves of a Xen pvSCSI driver utilize nodes within the XenStore to
   37  * communicate capabilities and to negotiate operating parameters.  This
   38  * section enumerates these nodes which reside in the respective front and
   39  * backend portions of the XenStore, following the XenBus convention.
   40  *
   41  * Any specified default value is in effect if the corresponding XenBus node
   42  * is not present in the XenStore.
   43  *
   44  * XenStore nodes in sections marked "PRIVATE" are solely for use by the
   45  * driver side whose XenBus tree contains them.
   46  *
   47  *****************************************************************************
   48  *                            Backend XenBus Nodes
   49  *****************************************************************************
   50  *
   51  *------------------ Backend Device Identification (PRIVATE) ------------------
   52  *
   53  * p-devname
   54  *      Values:         string
   55  *
   56  *      A free string used to identify the physical device (e.g. a disk name).
   57  *
   58  * p-dev
   59  *      Values:         string
   60  *
   61  *      A string specifying the backend device: either a 4-tuple "h:c:t:l"
   62  *      (host, controller, target, lun, all integers), or a WWN (e.g.
   63  *      "naa.60014054ac780582").
   64  *
   65  * v-dev
   66  *      Values:         string
   67  *
   68  *      A string specifying the frontend device in form of a 4-tuple "h:c:t:l"
   69  *      (host, controller, target, lun, all integers).
   70  *
   71  *--------------------------------- Features ---------------------------------
   72  *
   73  * feature-sg-grant
   74  *      Values:         unsigned [VSCSIIF_SG_TABLESIZE...65535]
   75  *      Default Value:  0
   76  *
   77  *      Specifies the maximum number of scatter/gather elements in grant pages
   78  *      supported. If not set, the backend supports up to VSCSIIF_SG_TABLESIZE
   79  *      SG elements specified directly in the request.
   80  *
   81  *****************************************************************************
   82  *                            Frontend XenBus Nodes
   83  *****************************************************************************
   84  *
   85  *----------------------- Request Transport Parameters -----------------------
   86  *
   87  * event-channel
   88  *      Values:         unsigned
   89  *
   90  *      The identifier of the Xen event channel used to signal activity
   91  *      in the ring buffer.
   92  *
   93  * ring-ref
   94  *      Values:         unsigned
   95  *
   96  *      The Xen grant reference granting permission for the backend to map
   97  *      the sole page in a single page sized ring buffer.
   98  *
   99  * protocol
  100  *      Values:         string (XEN_IO_PROTO_ABI_*)
  101  *      Default Value:  XEN_IO_PROTO_ABI_NATIVE
  102  *
  103  *      The machine ABI rules governing the format of all ring request and
  104  *      response structures.
  105  */
  106 
  107 /* Requests from the frontend to the backend */
  108 
  109 /*
  110  * Request a SCSI operation specified via a CDB in vscsiif_request.cmnd.
  111  * The target is specified via channel, id and lun.
  112  *
  113  * The operation to be performed is specified via a CDB in cmnd[], the length
  114  * of the CDB is in cmd_len. sc_data_direction specifies the direction of data
  115  * (to the device, from the device, or none at all).
  116  *
  117  * If data is to be transferred to or from the device the buffer(s) in the
  118  * guest memory is/are specified via one or multiple scsiif_request_segment
  119  * descriptors each specifying a memory page via a grant_ref_t, a offset into
  120  * the page and the length of the area in that page. All scsiif_request_segment
  121  * areas concatenated form the resulting data buffer used by the operation.
  122  * If the number of scsiif_request_segment areas is not too large (less than
  123  * or equal VSCSIIF_SG_TABLESIZE) the areas can be specified directly in the
  124  * seg[] array and the number of valid scsiif_request_segment elements is to be
  125  * set in nr_segments.
  126  *
  127  * If "feature-sg-grant" in the Xenstore is set it is possible to specify more
  128  * than VSCSIIF_SG_TABLESIZE scsiif_request_segment elements via indirection.
  129  * The maximum number of allowed scsiif_request_segment elements is the value
  130  * of the "feature-sg-grant" entry from Xenstore. When using indirection the
  131  * seg[] array doesn't contain specifications of the data buffers, but
  132  * references to scsiif_request_segment arrays, which in turn reference the
  133  * data buffers. While nr_segments holds the number of populated seg[] entries
  134  * (plus the set VSCSIIF_SG_GRANT bit), the number of scsiif_request_segment
  135  * elements referencing the target data buffers is calculated from the lengths
  136  * of the seg[] elements (the sum of all valid seg[].length divided by the
  137  * size of one scsiif_request_segment structure). The frontend may use a mix of
  138  * direct and indirect requests.
  139  */
  140 #define VSCSIIF_ACT_SCSI_CDB         1
  141 
  142 /*
  143  * Request abort of a running operation for the specified target given by
  144  * channel, id, lun and the operation's rqid in ref_rqid.
  145  */
  146 #define VSCSIIF_ACT_SCSI_ABORT       2
  147 
  148 /*
  149  * Request a device reset of the specified target (channel and id).
  150  */
  151 #define VSCSIIF_ACT_SCSI_RESET       3
  152 
  153 /*
  154  * Preset scatter/gather elements for a following request. Deprecated.
  155  * Keeping the define only to avoid usage of the value "4" for other actions.
  156  */
  157 #define VSCSIIF_ACT_SCSI_SG_PRESET   4
  158 
  159 /*
  160  * Maximum scatter/gather segments per request.
  161  *
  162  * Considering balance between allocating at least 16 "vscsiif_request"
  163  * structures on one page (4096 bytes) and the number of scatter/gather
  164  * elements needed, we decided to use 26 as a magic number.
  165  *
  166  * If "feature-sg-grant" is set, more scatter/gather elements can be specified
  167  * by placing them in one or more (up to VSCSIIF_SG_TABLESIZE) granted pages.
  168  * In this case the vscsiif_request seg elements don't contain references to
  169  * the user data, but to the SG elements referencing the user data.
  170  */
  171 #define VSCSIIF_SG_TABLESIZE             26
  172 
  173 /*
  174  * based on Linux kernel 2.6.18, still valid
  175  *
  176  * Changing these values requires support of multiple protocols via the rings
  177  * as "old clients" will blindly use these values and the resulting structure
  178  * sizes.
  179  */
  180 #define VSCSIIF_MAX_COMMAND_SIZE         16
  181 #define VSCSIIF_SENSE_BUFFERSIZE         96
  182 
  183 struct scsiif_request_segment {
  184     grant_ref_t gref;
  185     uint16_t offset;
  186     uint16_t length;
  187 };
  188 typedef struct scsiif_request_segment vscsiif_segment_t;
  189 
  190 #define VSCSIIF_SG_PER_PAGE (PAGE_SIZE / sizeof(struct scsiif_request_segment))
  191 
  192 /* Size of one request is 252 bytes */
  193 struct vscsiif_request {
  194     uint16_t rqid;          /* private guest value, echoed in resp  */
  195     uint8_t act;            /* command between backend and frontend */
  196     uint8_t cmd_len;        /* valid CDB bytes */
  197 
  198     uint8_t cmnd[VSCSIIF_MAX_COMMAND_SIZE]; /* the CDB */
  199     uint16_t timeout_per_command;   /* deprecated: timeout in secs, 0=default */
  200     uint16_t channel, id, lun;      /* (virtual) device specification */
  201     uint16_t ref_rqid;              /* command abort reference */
  202     uint8_t sc_data_direction;      /* for DMA_TO_DEVICE(1)
  203                                        DMA_FROM_DEVICE(2)
  204                                        DMA_NONE(3) requests  */
  205     uint8_t nr_segments;            /* Number of pieces of scatter-gather */
  206 /*
  207  * flag in nr_segments: SG elements via grant page
  208  *
  209  * If VSCSIIF_SG_GRANT is set, the low 7 bits of nr_segments specify the number
  210  * of grant pages containing SG elements. Usable if "feature-sg-grant" set.
  211  */
  212 #define VSCSIIF_SG_GRANT    0x80
  213 
  214     vscsiif_segment_t seg[VSCSIIF_SG_TABLESIZE];
  215     uint32_t reserved[3];
  216 };
  217 typedef struct vscsiif_request vscsiif_request_t;
  218 
  219 /*
  220  * The following interface is deprecated!
  221  */
  222 #define VSCSIIF_SG_LIST_SIZE ((sizeof(vscsiif_request_t) - 4) \
  223                               / sizeof(vscsiif_segment_t))
  224 
  225 struct vscsiif_sg_list {
  226     /* First two fields must match struct vscsiif_request! */
  227     uint16_t rqid;          /* private guest value, must match main req */
  228     uint8_t act;            /* VSCSIIF_ACT_SCSI_SG_PRESET */
  229     uint8_t nr_segments;    /* Number of pieces of scatter-gather */
  230     vscsiif_segment_t seg[VSCSIIF_SG_LIST_SIZE];
  231 };
  232 typedef struct vscsiif_sg_list vscsiif_sg_list_t;
  233 /* End of deprecated interface */
  234 
  235 /* Size of one response is 252 bytes */
  236 struct vscsiif_response {
  237     uint16_t rqid;          /* identifies request */
  238     uint8_t act;            /* deprecated: valid only if SG_PRESET supported */
  239     uint8_t sense_len;
  240     uint8_t sense_buffer[VSCSIIF_SENSE_BUFFERSIZE];
  241     int32_t rslt;
  242     uint32_t residual_len;     /* request bufflen - 
  243                                   return the value from physical device */
  244     uint32_t reserved[36];
  245 };
  246 typedef struct vscsiif_response vscsiif_response_t;
  247 
  248 DEFINE_RING_TYPES(vscsiif, struct vscsiif_request, struct vscsiif_response);
  249 
  250 
  251 #endif  /*__XEN__PUBLIC_IO_SCSI_H__*/
  252 /*
  253  * Local variables:
  254  * mode: C
  255  * c-file-style: "BSD"
  256  * c-basic-offset: 4
  257  * tab-width: 4
  258  * indent-tabs-mode: nil
  259  * End:
  260  */

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