attach() Entry Point (SCSI Target Drivers)

After the probe(9E) routine has verified that the expected device is present, attach(9E) is called. attach() performs these tasks:

• Allocates and initializes any per-instance data.

• Creates minor device node information.

• Restores the hardware state of a device after a suspension of the device or the system. See attach() Entry Point for details.

A SCSI target driver needs to call scsi_probe(9F) again to retrieve the device's inquiry data. The driver must also create a SCSI request sense packet. If the attach is successful, the attach() function should not call scsi_unprobe(9F).

Three routines are used to create the request sense packet: scsi_alloc_consistent_buf(9F), scsi_init_pkt(9F), and scsi_setup_cdb(9F). scsi_alloc_consistent_buf(9F) allocates a buffer that is suitable for consistent DMA. scsi_alloc_consistent_buf() then returns a pointer to a buf(9S) structure. The advantage of a consistent buffer is that no explicit synchronization of the data is required. In other words, the target driver can access the data after the callback. The sd_sense element of the device's scsi_device(9S) structure must be initialized with the address of the sense buffer. scsi_init_pkt(9F) creates and partially initializes a scsi_pkt(9S) structure. scsi_setup_cdb(9F) creates a SCSI command descriptor block, in this case by creating a SCSI request sense command.

Note that a SCSI device is not self-identifying and does not have a reg property. As a result, the driver must set the pm-hardware-state property. Setting pm-hardware-state informs the framework that this device needs to be suspended and then resumed.

The following example shows the SCSI target driver's attach() routine.

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);
}