attach() 入口点（SCSI 目标驱动程序）

在 probe(9E) 例程验证预期设备是否存在后，将调用 attach(9E)。attach() 执行以下任务：

• 分配并初始化任何每实例数据。

• 创建从设备节点信息。

• 暂停设备或系统后恢复设备的硬件状态。有关详细信息，请参见attach() Entry Point。

SCSI 目标驱动程序需要再次调用 scsi_probe(9F)，以检索设备的查询数据。该驱动程序还必须创建 SCSI 请求检测包。如果连接成功，则 attach() 函数不应调用 scsi_unprobe(9F)。

以下三个例程可用于创建请求检测包：scsi_alloc_consistent_buf(9F)、scsi_init_pkt(9F) 和 scsi_setup_cdb(9F)。scsi_alloc_consistent_buf(9F) 分配适用于一致 DMA 的缓冲区。然后，scsi_alloc_consistent_buf() 返回指向 buf(9S) 结构的指针。一致缓冲区的优点在于无需显式同步数据。换句话说，目标驱动程序可以在回调之后访问数据。必须使用检测缓冲区的地址初始化设备的 scsi_device(9S) 结构的 sd_sense 元素。scsi_init_pkt(9F) 创建并部分初始化 scsi_pkt(9S) 结构。scsi_setup_cdb(9F) 创建 SCSI 命令描述符块，此时是通过创建 SCSI 请求检测命令来实现。

请注意，SCSI 设备不是自标识设备，并且没有 reg 属性。因此，驱动程序必须设置 pm-hardware-state 属性。设置 pm-hardware-state 将会通知框架需要暂停该设备然后将其恢复。

以下示例显示了 SCSI 目标驱动程序的 attach() 例程。

static int
xxattach(dev_info_t *dip, ddi_attach_cmd_t cmd)
{
    struct xxstate         *xsp;
    struct scsi_pkt        *rqpkt = NULL;
    struct scsi_device     *sdp;
    struct buf         *bp = NULL;
    int            instance;
    instance = ddi_get_instance(dip);
    switch (cmd) {
      case DDI_ATTACH:
          break;
      case DDI_RESUME:
          /* For information, see the "Directory Memory Access (DMA)" */
          /* chapter in this book. */
      default:
          return (DDI_FAILURE);
    }
    /*
     * Allocate a state structure and initialize it.
     */
    xsp = ddi_get_soft_state(statep, instance);
    sdp = (struct scsi_device *)ddi_get_driver_private(dip);
    /*
     * Cross-link the state and scsi_device(9S) structures.
     */
    sdp->sd_private = (caddr_t)xsp;
    xsp->sdp = sdp;
    /*
     * Call scsi_probe(9F) again to get and validate inquiry data.
     * Allocate a request sense buffer. The buf(9S) structure
     * is set to NULL to tell the routine to allocate a new one.
     * The callback function is set to NULL_FUNC to tell the
     * routine to return failure immediately if no
     * resources are available.
     */
    bp = scsi_alloc_consistent_buf(&sdp->sd_address, NULL,
    SENSE_LENGTH, B_READ, NULL_FUNC, NULL);
    if (bp == NULL)
        goto failed;
    /*
     * Create a Request Sense scsi_pkt(9S) structure.
     */
    rqpkt = scsi_init_pkt(&sdp->sd_address, NULL, bp,
    CDB_GROUP0, 1, 0, PKT_CONSISTENT, NULL_FUNC, NULL);
    if (rqpkt == NULL)
        goto failed;
    /*
     * scsi_alloc_consistent_buf(9F) returned a buf(9S) structure.
     * The actual buffer address is in b_un.b_addr.
     */
    sdp->sd_sense = (struct scsi_extended_sense *)bp->b_un.b_addr;
    /*
     * Create a Group0 CDB for the Request Sense command
     */
    if (scsi_setup_cdb((union scsi_cdb *)rqpkt->pkt_cdbp,
        SCMD_REQUEST_SENSE, 0, SENSE__LENGTH, 0) == 0)
        goto failed;;
    /*
     * Fill in the rest of the scsi_pkt structure.
     * xxcallback() is the private command completion routine.
     */
    rqpkt->pkt_comp = xxcallback;
    rqpkt->pkt_time = 30; /* 30 second command timeout */
    rqpkt->pkt_flags |= FLAG_SENSING;
    xsp->rqs = rqpkt;
    xsp->rqsbuf = bp;
    /*
     * Create minor nodes, report device, and do any other initialization. */
     * Since the device does not have the 'reg' property,
     * cpr will not call its DDI_SUSPEND/DDI_RESUME entries.
     * The following code is to tell cpr that this device
     * needs to be suspended and resumed.
     */
    (void) ddi_prop_update_string(device, dip,
        "pm-hardware-state", "needs-suspend-resume");
    xsp->open = 0;
    return (DDI_SUCCESS);
failed:
    if (bp)
        scsi_free_consistent_buf(bp);
    if (rqpkt)
        scsi_destroy_pkt(rqpkt);
    sdp->sd_private = (caddr_t)NULL;
    sdp->sd_sense = NULL;
    scsi_unprobe(sdp);
    /* Free any other resources, such as the state structure. */
    return (DDI_FAILURE);
}